%0 journal article %@ 1948-7185 %A Cheng, Z.,Guan, Y.,Wen, H.,Li, Z.,Cui, K.,Pei, Q.,Wang, S.,Pistidda, C.,Guo, J.,Cao, H.,Chen, P. %D 2024 %J The Journal of Physical Chemistry Letters %N 25 %P 6662–6667 %R doi:10.1021/acs.jpclett.4c00874 %T Light-Driven De/Rehydrogenation of a LiH Surface under Ambient Conditions %U https://doi.org/10.1021/acs.jpclett.4c00874 25 %X Lithium hydride (LiH), a saline hydride with a hydrogen density of 12.6 wt %, is highly thermostable, which hinders its extensive application in hydrogen storage. In this study, we demonstrate a distinct photodecomposition of LiH under ambient conditions. Ultraviolet–visible (UV–vis) illumination induces hydrogen release and creates surface hydrogen vacancies on LiH. The subsequent H– migration enables hydrogen desorption and the accumulation of vacancies at the subsurface, resulting in the generation of metallic Li clusters. Rehydrogenation, on the contrary, can be charged under UV–vis illumination in 1 bar H2. Such phenomena show that the thermodynamic and kinetic limits in the re/dehydrogenation of LiH can be broken under illumination, which allows hydrogen storage over the LiH surface at temperatures ∼600 K lower than those of the corresponding thermal process. This work provides new insights into the interaction of semiconducting hydrides and photons and opens an avenue for the development and optimization of materials for hydrogen storage and related photodriven reactions. %0 journal article %@ 1359-6462 %A Shang, Y.,Santhosh, A.,Jerabek, P.,Klassen, T.,Pistidda, C. %D 2024 %J Scripta Materialia %N %P 115837 %R doi:10.1016/j.scriptamat.2023.115837 %T First-principles study on interfacial property in MgB2-based reactive hydride composites %U https://doi.org/10.1016/j.scriptamat.2023.115837 %X The underlying physico-chemical interactions between transition metal-based boride particles that formed during the dehydrogenation process and MgB2 in 2LiBH4+MgH2 reactive hydride composite at the atomic scale are still unknown. In this work, the properties of the TiB2/MgB2 interface were investigated by first-principles calculations utilizing density functional theory (DFT). Taking the two terminations of both MgB2 and TiB2 as well as four different stacking sequences into account, energies of the TiB2 and MgB2 (0001) surfaces as well as the work of adhesion and the electronic structure of the interfaces were studied. The results show that the interface between the B-terminated MgB2 (0001) surface and the Ti-terminated TiB2 (0001) surface is the energetically most favorable among all four stacking options and possesses the largest work of adhesion. Our results further show that the TiB2 particles possess good nucleation potency for MgB2 particles from the thermodynamic perspective. %0 journal article %@ 0364-5916 %A Hannappel, P.,Alvares, E.,Heubner, F.,Pistidda, C.,Jerabek, P.,Weißgärber, T. %D 2024 %J Calphad %N %P 102701 %R doi:10.1016/j.calphad.2024.102701 %T Thermodynamic assessment of the Ce-H and CeNi5-H system %U https://doi.org/10.1016/j.calphad.2024.102701 %X Interstitial metal hydrides (MHs) have attracted considerable attention in the field of hydrogen technology, particularly in the context of storage and compression applications. Because of their minor hysteresis effects, good cyclability, activation simplicity, and high volumetric storage density, LaNi5-based alloys are recognized as prominent candidates for hydrogen storage application. Additionally, the system’s thermodynamic and electrochemical properties can be modified to suit the requirements of a particular application by alloying specific substituents. To ascertain the thermodynamic effects of Ce addition within LaNi5, in this work the Ce-H and CeNi5-H systems have been modeled with the CALPHAD method. For this reason, in this work, two different thermodynamic models have been developed and assessed using the same pressure-composition isotherms (PCIs) datasets obtained from literature and theoretical formation energies newly calculated employing periodic density functional theory (DFT). Direct comparison of the models against each other in terms of accuracy and physical plausibility revealed that extrapolation of thermodynamic properties to data-scarce regions is more reasonable with fewer model parameters and in agreement with other similar systems within the rare-earth (RE) metal-hydride class. In addition, the CeNi5-H system was investigated by assessing the (Ce)(Ni)5 (V a,H)7 phase model, which could accurately predict hydrogen storage properties while being compatible with previously developed LaNi5-H models. Ultimately, the models developed in this study may be employed and extended to describe multi-component RE-H systems and allow for thermodynamic computations that are highly desirable for accurate predictions of hydrogen absorption/desorption properties and degradation characteristics within the (La,Ce)Ni5-H metal hydride family. %0 journal article %@ 0020-1669 %A Le, T.T.,Bordignon, S.,Chierotti, M.R.,Shang, Y.,Schökel, A.,Klassen, T.,Pistidda, C. %D 2024 %J Inorganic Chemistry %N 24 %P 11233-11241 %R doi:10.1021/acs.inorgchem.4c01016 %T Mixed Metal Amide-Hydride Solid Solutions for Potential Energy Storage Applications %U https://doi.org/10.1021/acs.inorgchem.4c01016 24 %X Mixed solid solutions have played an important role in improving the kinetics and performance of hydrogen storage materials, as reported for the Li–Mg–N–H, K–Mg–N–H, and Rb–Mg–N–H systems. Besides, the formation of a homogeneous solid solution, mostly due to partial ionic substitution, is known to be an effective approach to improve the ionic conductivity of a material, which is an important property in electrochemical applications. We have reported a series of solid solutions based on mixed amide-hydride materials of the Group 1 elements, e.g., K(NH2)xH1–x, Rb(NH2)xH1–x, and Cs(NH2)xH1–x, via the exchange of NH2–/H– anions with the change of the lattice cell of the solid solution. Extending the research in this direction, we study the M–N–H solid solution in the MNH2–MH systems (M = K, Rb, Cs, and their combinations), i.e., KNH2–RbH, RbNH2–KH, RbNH2–CsH, and CsNH2–RbH via ex situ/in situ XRD, IR, and 1H 2D solid-state NMR. The results obtained confirm the formation of mixed metal amide-hydride solid solutions associated with an exchange between both anionic (NH2– and H–) and cationic species (K+, Rb+, and Cs+). With this study, we aim to create an accessible library of M–N–H solid solutions for further studies as additives for hydrogen storage materials or ionic conductors. %0 journal article %@ 1359-6454 %A Choisez, L.,Hemke, K.,Özgün, Ö.,Pistidda, C.,Jeppesen, H.,Raabe, D.,Ma, Y. %D 2024 %J Acta Materialia %N %P 119752 %R doi:10.1016/j.actamat.2024.119752 %T Hydrogen-based direct reduction of combusted iron powder: deep pre-oxidation; reduction kinetics and microstructural analysis %U https://doi.org/10.1016/j.actamat.2024.119752 %X Iron powder can be a sustainable alternative to fossil fuels in power supply due to its high energy density and abundance. Iron powder releases energy through exothermic oxidation (combustion), and stores back energy through its subsequent hydrogen-based reduction, establishing a circular loop for renewable energy supply. Hydrogen-based direct reduction is also gaining global momentum as possible future backbone technology for sustainable iron and steel production, with the aim to replace blast furnaces. Here, we investigate the microstructural formation mechanisms and reduction kinetics behind hydrogen-based direct reduction of combusted iron powder at moderate temperatures (400–500 °C) using thermogravimetry, ex-situ X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and electron backscatter diffraction, as well as in-situ high-energy X-ray diffraction. The influence of pre-oxidation treatment was studied by reducing both as-combusted iron powder (50 % magnetite and 50 % hematite) and the same powder after pre-oxidation (100 % hematite). A gas diffusion-limited reaction was obtained during the in-situ high-energy X-ray diffraction experiment, with successive hematite and magnetite reduction, and a strong increase in reduction kinetics with initial hematite content. Faster reduction kinetics were obtained during the thermogravimetry experiment, with simultaneous hematite and magnetite reduction. In this case, the reduction reaction was limited by a mix of phase boundary and nucleation and growth models, as analyzed by multi-step model fitting methods as well as by microstructural investigation. When not limited by gas diffusion, the pre-oxidation treatment showed almost no influence on the reduction time but a strong effect on the final microstructure of the reduced powder. %0 journal article %@ 1438-1656 %A Hieke, S.W.,Frank, A.,Duarte, M. J.,Gopalan, H.,Patil, P.,Wetegrove, M.,Rohloff, M.,Kruth, A.,Pistidda, C.,Dornheim, M.,Taube, K.,Dehm, G.,Scheu, C. %D 2024 %J Advanced Engineering Materials %N 4 %P 2300619 %R doi:doi.org/10.1002/adem.202300619 %T Stability and Failure Mechanisms of Al2O3|Al Bilayer Coatings Exposed to 300 Bar Hydrogen at 673 K %U https://doi.org/doi.org/10.1002/adem.202300619 4 %X Hydrogen barrier coatings are important for future hydrogen economy to enable materials for applications in hydrogen tanks. In the present study, coatings consisting of amorphous Al2O3 (≈100 nm) synthesized by plasma ion-assisted deposition on top of crystalline metallic Al (≈100 nm) are exposed to 300 bar hydrogen pressure at 673 K for 6 days. This is done to mimic and accelerate conditions in hydrogen storage containers for metallic hydrides. They remain intact after such harsh conditions, although changes do occur. Blister-like features are observed consisting of a buckled oxide layer while the metallic Al layer underneath is retracted. As these features are also found for coatings annealed under 1 bar Ar atmosphere it is concluded that they are not related to the formation of gas bubbles but they form due to solid-state dewetting. This is different to literature observation where H2 bubbles are reported as a consequence of interface diffusion of H/H+ species present due to the initial precursor used for film deposition. The mechanical properties of the coatings, which are evaluated from nanoindentation load–displacement curves, change only moderately. Overall, the study shows that Al2O3|Al coatings are suitable candidates to prevent hydrogen ingress, but dewetting due to long-term exposure at elevated temperatures must be prevented. %0 journal article %@ 2590-1230 %A Le, T.,Santhosh, A.,Bordignon, S.,Chierotti, M.,Jerabek, P.,Klassen, T.,Pistidda, C. %D 2023 %J Results in Engineering %N %P 100895 %R doi:10.1016/j.rineng.2023.100895 %T Experimental and computational studies on the formation of mixed amide-hydride solid solutions for CsNH2–CsH system %U https://doi.org/10.1016/j.rineng.2023.100895 %X In this study, experimental determination and computational prediction are combined to investigate the formation of a mixed amide-hydride solid solution for the CsNH2–CsH system in a wide compositional range. The experimentally obtained results strongly indicate that a complete amide-hydride solid solution Cs(NH2)xH1-x with a stable cubic structure is achievable when the molar fraction of amide (x) is lower than 0.9. These results validate and confirm our data computationally via first-principles calculations, including the simulations of infrared (IR) and nuclear magnetic resonance (NMR) spectra for structures of various compositions as well as the determination of the dipolar coupling constants. Both the computed vibrational frequencies and 1H chemical shifts of CsNH2 and CsH moieties in the Cs(NH2)xH1-x (x = 0.2, 0.5, 0.8, 1) solid solution structures agree with the experimental IR and 1H MAS NMR data of the mixed xCsNH2+(1-x)CsH samples, confirming the formation of the solid solutions. The closest interproton distance in the homogeneous Cs(NH2)0·5H0.5 solid solution is computed to be 3.67 Å, which is larger than that of the known Rb(NH2)0·5H0.5 solid solution (3.29 Å). This work's combination of theoretical research and experimentation provides a suitable framework for the structural analysis and property estimation of other M-N-H solid solutions. %0 journal article %@ 0925-8388 %A Warfsmann, J.,Puszkiel, J.A.,Passing, M.,Krause, P.S.,Wienken, E.,Taube, K.,Klassen, T.,Pistidda, C.,Jepsen, J. %D 2023 %J Journal of Alloys and Compounds %N %P 169814 %R doi:10.1016/j.jallcom.2023.169814 %T Applying wash coating techniques for swelling-induced stress reduction and thermal improvement in metal hydrides %U https://doi.org/10.1016/j.jallcom.2023.169814 %X The storage of hydrogen in metal alloys as an alternative to hydrogen storage in pressurized or liquid form has the advantage of high volumetric storage capacity and less complex storage systems due to lower pressure and moderate temperature conditions. The later leads to an improved safety and reduced cost of the storage vessel. However, when considering their utilization in hydrogen storage tanks, swelling-induced stress and heat management are challenges that still require to be addressed. Several strategies have been published in the past to address these problems, however it can be challenging to scale them up. In this work, we propose an easily scalable approach to overcome these drawbacks. The commercially available AB2 room-temperature metal alloy Hydralloy C5 was modified by applying a wash coating-like methodology. The surface of the metal alloy was coated with a mixture of a conductive material like expanded natural graphite (ENG) or aluminum and the elastomeric ethylene-vinyl acetate copolymer (EVA). The performance of this modified metal alloy was investigated by in situ measurement of hydrogen capacity, heat dissipation and swelling-induced stress during 50 hydrogenation/dehydrogenation cycles. The coated metal alloy maintained a satisfactory hydrogen capacity with slightly improved heat dissipation. The swelling-induced stress behavior of the treated material was greatly improved. Especially the addition of a mixture of 10 wt% ENG and 10 wt% EVA allowed to completely compensate for the swelling-induced stress during hydrogenation. %0 journal article %@ 2050-7488 %A Santhosh, A.,Kang, S.,Keilbart, N.,Wood, B.C.,Klassen, T.,Jerabek, P.,Dornheim, M. %D 2023 %J Journal of Materials Chemistry A %N %P 18776-18789 %R doi:10.1039/D3TA02205F %T Influence of near-surface oxide layers on TiFe hydrogenation - Mechanistic insights and implications for hydrogen storage applications %U https://doi.org/10.1039/D3TA02205F %X The inevitable formation of passivating oxide films on the surface of the TiFe intermetallic compound limits its performance as a stationary hydrogen storage material. Extensive experimental efforts have been dedicated to the activation of TiFe, i.e. oxide layer removal prior to utilization for hydrogen storage. However, development of an efficient activation protocol necessitates a fundamental understanding of the composition and structure of the air-exposed surface and its interaction with hydrogen, which is currently absent. Therefore, in this study we explored the growth and nature of oxide films on the most exposed TiFe surface (110) in depth using static and dynamic first-principles methods. We identified the lowest energy structures for six oxygen coverages up to approximately 1.12 nm of thickness with a global optimization method and studied the temperature effects and structural evolution of the oxide phases in detail via ab initio molecular dynamics (AIMD). Based on structural similarity and coordination analysis, motifs for TiO2 and TiFeO3 as well as Ti(FeO2)x (x = 2, 3 or 5) phases were identified. On evaluating the interaction of the oxidized surface with hydrogen, a minimal energy barrier of 0.172 eV was predicted for H2 dissociation while H migration from the top of the oxidized surface to the bulk TiFe was limited by several high-lying energy barriers above 1.4 eV. Our mechanistic insights will prove themselves valuable for informed designs towards new activation methods of TiFe and related systems as hydrogen storage materials. %0 journal article %@ 1369-7021 %A Shang, Y.,Lei, Z.,Alvares, E.,Garroni, S.,Chen, T.,Dore, R.,Rustici, M.,Enzo, S.,Schökel, A.,Shi, Y.,Jerabek, P.,Lu, Z.,Klassen, T.,Pistidda, C. %D 2023 %J Materials Today %N %P 113-126 %R doi:10.1016/j.mattod.2023.06.012 %T Ultra-lightweight compositionally complex alloys with large ambient-temperature hydrogen storage capacity %U https://doi.org/10.1016/j.mattod.2023.06.012 %X In the burgeoning field of hydrogen energy, compositionally complex alloys promise unprecedented solid-state hydrogen storage applications. However, compositionally complex alloys are facing one main challenge: reducing alloy density and increasing hydrogen storage capacity. Here, we report TiMgLi-based compositionally complex alloys with ultralow alloy density and significant room-temperature hydrogen storage capacity. The record-low alloy density (2.83 g cm−3) is made possible by multi-principal-lightweight element alloying. Introducing multiple phases instead of a single phase facilitates obtaining a large hydrogen storage capacity (2.62 wt% at 50 °C under 100 bar of H2). The kinetic modeling results indicate that three-dimensional diffusion governs the hydrogenation reaction of the current compositionally complex alloys at 50 °C. The here proposed approach broadens the horizon for designing lightweight compositionally complex alloys for hydrogen storage purposes. %0 journal article %@ 1385-8947 %A Le, T.T.,Abbas, M.,Dreistadt, D.M.,Klassen, T.,Pistidda, C. %D 2023 %J Chemical Engineering Journal %N %P 145315 %R doi:10.1016/j.cej.2023.145315 %T Ionic conductivity in complex hydrides for energy storage applications: A comprehensive review %U https://doi.org/10.1016/j.cej.2023.145315 %X In recent years, complex hydrides have been extensively studied for energy storage and conversion applications. In particular, the possibility of using this class of materials as solid ionic electrolytes is attracting increasing interest. This review aims at providing a comprehensive overview of ionic conduction in complex hydrides containing various monovalent (Li+, Na+, and K+) and multivalent (Mg2+) ions. Possible approaches to enhance the ionic conductivity of complex hydrides such as ionic substitution, nanoconfinement, interface engineering, and composite formation are highlighted, and the associated conduction mechanisms are discussed. The use of complex hydrides as solid electrolytes for electrochemical conversion and storage applications is then reviewed, including potential applications, challenges, and our perspectives. Finally, the relationship between ionic conduction and hydrogen sorption properties of complex hydrides is briefly discussed. %0 journal article %@ 2753-1457 %A Fogel, S.,Yeates, C.,Unger, S.,Rodriguez-Garcia, G.,Baetcke, L.,Dornheim, M.,Schmidt-Hattenberger, C.,Bruhn, D.,Hampel, U. %D 2022 %J Energy Advances %N %P 402-421 %R doi:10.1039/D1YA00035G %T SNG based energy storage systems with subsurface CO2 storage %U https://doi.org/10.1039/D1YA00035G %X Large-scale energy storage plants based on power-to-gas-to-power (PtG–GtP) technologies incorporating high temperature electrolysis, catalytic methanation for the provision of synthetic natural gas (SNG) and novel, highly efficient SNG-fired Allam reconversion cycles allow for a confined and circular use of CO2/CH4 and thus an emission-free storage of intermittent renewable energy. This study features a thorough technology assessment for large-scale PtG–GtP storage plants based on highly efficient sCO2 power cycles combined with subsurface CO2 storage. The Allam cycle employs supercritical CO2 as working fluid as well as an oxy-combustion process to reach high efficiencies of up to 66%. The entire PtG–GtP process chain assessed in this study is expected to reach maximum roundtrip efficiencies of 54.2% (with dedicated and sufficient O2 storage) or 49.0% (with a dedicated air separation unit). The implementation of said energy storage systems into existing national energy grids will pose a major challenge, since they will require far-reaching infrastructural changes to the respective systems, such as extensive installations of renewable generation and electrolysis capacities as well as sufficient subsurface storage capacities for both CO2 and CH4. Therefore, this study incorporates an assessment of the present subsurface storage potential for CO2 and CH4 in Germany. Furthermore, a basic forecast study for the German energy system with an assumed mass deployment of the proposed SNG-based PtG–GtP energy storage system for the year 2050 is conducted. In case of a fully circular use of CO2/CH4, when electricity is solely generated by renewable energy sources, 736 GW of renewables, 234 GW of electrolysis and 62 GW of gas-to-power capacities are required in the best case scenario in 2050. The total storage volume on the national scale of Germany for both CO2 and CH4 was determined to be 7.8 billion N m3, respectively, leading to a CH4 storage capacity of 54.5 TW h. The presented investigations illustrate the feasibility of large-scale energy storage systems for renewable electricity based on high temperature electrolysis, catalytic methanation and Allam power cycles paired with large subsurface storages for CO2 and CH4. %0 journal article %@ 2365-709X %A Abetz, C.,Georgopanos, P.,Pistidda, C.,Klassen, T.,Abetz, V. %D 2022 %J Advanced Materials Technologies %N 11 %P 2101584 %R doi:10.1002/admt.202101584 %T Reactive Hydride Composite Confined in a Polymer Matrix: New Insights into the Desorption and Absorption of Hydrogen in a Storage Material with High Cycling Stability %U https://doi.org/10.1002/admt.202101584 11 %X Hydrogen is key to the transformation of today's energy technology toward a sustainable future without carbon dioxide emissions. Hydrogen can be produced from water using renewable or sustainable energy sources such as solar or wind power. It can buffer fluctuations between energy generation and use in all energy sectors, stationary heat, and power, as well as mobility. Safe, fast, and easy to handle solutions for storing and releasing hydrogen are essential for the implementation of hydrogen technology. Among the storage alternatives, metal hydride materials represent a safe and efficient option. For the first time, detailed investigations of the local chemical changes in a confined hydrogen storage material before and after 21 hydrogen-unloading and loading cycles are reported. The system is based on micrometer-sized reactive hydride composite (RHC) particles, namely 6Mg(NH2)2 + 9LiH + 1LiBH4, dispersed in a matrix of poly(4-methyl-1-pentene) (TPXTM). The morphological stability of the confined RHC particles during the reversible and almost complete reaction with hydrogen is visualized in detail, explaining the excellent long-term cycling stability. %0 journal article %@ 2071-1050 %A Cao, H.,Pistidda, C.,Richter, T.M.M.,Capurso, G.,Milanese, C.,Tseng, J.-C.,Shang, Y.,Niewa, R.,Chen, P.,Klassen, T.,Dornheim, M. %D 2022 %J Sustainability %N 3 %P 1672 %R doi:10.3390/su14031672 %T De-hydrogenation/Rehydrogenation Properties and Reaction Mechanism of AmZn(NH2)n-2nLiH Systems (A = Li, K, Na, and Rb) %U https://doi.org/10.3390/su14031672 3 %X With the aim to find suitable hydrogen storage materials for stationary and mobile applications, multi-cation amide-based systems have attracted considerable attention, due to their unique hydrogenation kinetics. In this work, AmZn(NH2)n (with A = Li, K, Na, and Rb) were synthesized via an ammonothermal method. The synthesized phases were mixed via ball milling with LiH to form the systems AmZn(NH2)n-2nLiH (with m = 2, 4 and n = 4, 6), as well as Na2Zn(NH2)4∙0.5NH3-8LiH. The hydrogen storage properties of the obtained materials were investigated via a combination of calorimetric, spectroscopic, and diffraction methods. As a result of the performed analyses, Rb2Zn(NH2)4-8LiH appears as the most appealing system. This composite, after de-hydrogenation, can be fully rehydrogenated within 30 s at a temperature between 190 °C and 200 °C under a pressure of 50 bar of hydrogen. %0 journal article %@ 2213-9567 %A Passing, M.,Pistidda, C.,Capurso, G.,Jepsen, J.,Metz, O.,Dornheim, M.,Klassen, T. %D 2022 %J Journal of Magnesium and Alloys %N 10 %P 2761-2774 %R doi:10.1016/j.jma.2021.12.005 %T Development and experimental validation of kinetic models for the hydrogenation/dehydrogenation of Mg/Al based metal waste for energy storage %U https://doi.org/10.1016/j.jma.2021.12.005 10 %X With the increased use of renewable energy sources, the need to store large amounts of energy will become increasingly important in the near future. A cost efficient possibility is to use the reaction of recycled Mg waste with hydrogen as thermo-chemical energy storage. Owing to the high reaction enthalpy, the moderate pressure and appropriate temperature conditions, the broad abundance and the recyclability, the Mg/Al alloy is perfectly suitable for this purpose. As further development of a previous work, in which the performance of recycled Mg/Al waste was presented, a kinetic model for hydro- and dehydrogenation is derived in this study. Temperature and pressure dependencies are determined, as well as the rate limiting step of the reaction. First experiments are carried out in an autoclave with a scaled-up powder mass, which is also used to validate the model by simulating the geometry with the scaled-up experiments at different conditions. %0 journal article %@ 0022-2461 %A Gizer, G.,Karimi, F.,Pistidda, C.,Cao, H.,Puszkiel, J.,Shang, Y.,Gericke, E.,Hoell, A.,Pranzas, K.,Klassen, T.,Dornheim, M. %D 2022 %J Journal of Materials Science %N 22 %P 10028-10038 %R doi:10.1007/s10853-022-06985-4 %T Effect of the particle size evolution on the hydrogen storage performance of KH doped Mg(NH2)2 + 2LiH %U https://doi.org/10.1007/s10853-022-06985-4 22 %X In recent years, many solid-state hydride-based materials have been considered as hydrogen storage systems for mobile and stationary applications. Due to a gravimetric hydrogen capacity of 5.6 wt% and a dehydrogenation enthalpy of 38.9 kJ/mol H2, Mg(NH2)2 + 2LiH is considered a potential hydrogen storage material for solid-state storage systems to be coupled with PEM fuel cell devices. One of the main challenges is the reduction of dehydrogenation temperature since this system requires high dehydrogenation temperatures (~ 200 °C). The addition of KH to this system significantly decreases the dehydrogenation onset temperature to 130 °C. On the one hand, the addition of KH stabilizes the hydrogen storage capacity. On the other hand, the capacity is reduced by 50% (from 4.1 to 2%) after the first 25 cycles. In this work, the particle sizes of the overall hydride matrix and the potassium-containing species are investigated during hydrogen cycling. Relation between particle size evolution of the additive and hydrogen storage kinetics is described by using an advanced synchrotron-based technique: Anomalous small-angle X-ray scattering, which was applied for the first time at the potassium K-edge for amide-hydride hydrogen storage systems. The outcomes from this investigation show that, the nanometric potassium-containing phases might be located at the reaction interfaces, limiting the particle coarsening. Average diameters of potassium-containing nanoparticles double after 25 cycles (from 10 to 20 nm). Therefore, reaction kinetics at subsequent cycles degrade. The deterioration of the reaction kinetics can be minimized by selecting lower absorption temperatures, which mitigates the particle size growth, resulting in two times faster reaction kinetics. %0 journal article %@ 0364-5916 %A Alvares, E.,Jerabek, P.,Shang, Y.,Santhosh, A.,Pistidda, C.,Heo, T.,Sundman, B.,Dornheim, M. %D 2022 %J Calphad %N %P 102426 %R doi:10.1016/j.calphad.2022.102426 %T Modeling the thermodynamics of the FeTi hydrogenation under para-equilibrium: An ab-initio and experimental study %U https://doi.org/10.1016/j.calphad.2022.102426 %X FeTi-based hydrides have recently re-attracted attention as stationary hydrogen storage materials due to favorable reversibility, good sorption kinetics and relatively low costs compared to alternative intermetallic hydrides. Employing the OpenCalphad software, the thermodynamics of the (FeTi)H (0 1) system were assessed as a key basis for modeling hydrogenation of FeTi-based alloys. New thermodynamic data were acquired from our experimental pressure-composition-isotherm (PCI) curves, as well as first-principles calculations utilizing density functional theory (DFT). The thermodynamic phase models were carefully selected based on critical analysis of literature information and ab-initio investigations. Key thermodynamic properties such as dissociation pressure, formation enthalpies and phase diagrams were calculated in good agreement to our performed experiments and literature-reported data. This work provides an initial perspective, which can be extended to account for higher-order thermodynamic assessments and subsequently enables the design of novel FeTi-based hydrides. In addition, the assessed thermodynamic data can serve as key inputs for kinetic models and hydride microstructure simulations. %0 journal article %@ 1463-9262 %A Shang, Y.,Pistidda, C.,Milanese, C.,Girella, A.,Schökel, A.,Le, T.,Hagenah, A.,Metz, O.,Klassen, T.,Dornheim, M. %D 2022 %J Green Chemistry %N 10 %P 4153-4163 %R doi:10.1039/D1GC04709D %T Sustainable NaAlH4 production from recycled automotive Al alloy %U https://doi.org/10.1039/D1GC04709D 10 %X To reduce the carbon footprint associated with the production of hydrogen storage materials and to reduce their cost, we pursue the possibility of obtaining high-quality hydride-based materials from industrial metals waste. In particular, in this manuscript, we propose a method for obtaining high-quality NaAlH4, starting from the Al-based automotive recycled alloy DIN-GDAlSi10Mg(Cu). The hydrogen storage properties of the material obtained by ball milling NaH and DIN-GDAlSi10Mg(Cu) under a hydrogen atmosphere were comprehensively explored via a broad range of experimental techniques, e.g. volumetric analysis, ex situ X-ray diffraction (XRD), in situ synchrotron radiation powder X-ray diffraction (SR-PXD), scanning electron microscopy (SEM), and differential thermal analysis (DTA). These investigations show that NaAlH4 was successfully synthesized and that its properties are comparable with those of high-purity commercial NaAlH4. %0 journal article %@ 0925-8388 %A Dreistadt, D.,Le, T.,Capurso, G.,Bellosta von Colbe, J.,Santhosh, A.,Pistidda, C.,Scharnagl, N.,Ovri, H.,Milanese, C.,Jerabek, P.,Klassen, T.,Jepsen, J. %D 2022 %J Journal of Alloys and Compounds %N %P 165847 %R doi:10.1016/j.jallcom.2022.165847 %T An effective activation method for industrially produced TiFeMn powder for hydrogen storage %U https://doi.org/10.1016/j.jallcom.2022.165847 %X This work proposes an effective thermal activation method with low technical effort for industrially produced titanium-iron-manganese powders (TiFeMn) for hydrogen storage. In this context, the influence of temperature and particle size of TiFeMn on the activation process is systematically studied. The results obtained from this investigation suggest that the activation of the TiFeMn material at temperatures as low as 50 °C is already possible, with a combination of “Dynamic” and “Static” routines, and that an increase to 90 °C strongly reduces the incubation time for activation, i.e. the incubation time of the sample with the two routines at 90 °C is about 0.84 h, while ∼ 277 h is required for the sample treated at 50 °C in both “Dynamic” and “Static” sequences. Selecting TiFeMn particles of larger size also leads to significant improvements in the activation performance of the investigated material. The proposed activation routine makes it possible to overcome the oxide layer existing on the compound surface, which acts as a diffusion barrier for the hydrogen atoms. This activation method induces further cracks and defects in the powder granules, generating new surfaces for hydrogen absorption with greater frequency, and thus leading to faster sorption kinetics in the subsequent absorption-desorption cycles. %0 journal article %@ 0360-3199 %A Shang, Y.,Jin, O.,Puszkiel, J.,Karimi, F.,Dansirima, P.,Sittiwet, C.,Utke, R.,Soontaranon, S.,Le, T.,Gizer, G.,Szabó, D.,Wagner, S.,Kübel, C.,Klassen, T.,Dornheim, M.,Pundt, A.,Pistidda, C. %D 2022 %J International Journal of Hydrogen Energy %N 89 %P 37882-37894 %R doi:10.1016/j.ijhydene.2022.08.293 %T Effects of metal-based additives on dehydrogenation process of 2NaBH4 + MgH2 system %U https://doi.org/10.1016/j.ijhydene.2022.08.293 89 %X We report a systematic investigation of the effect that selected metal-based additives have on the dehydrogenation properties of the reactive hydride composite (RHC) model system 2NaBH4+MgH2. Compared to the pristine system, the material doped with 3TiCl3·AlCl3 exhibits superior dehydrogenation kinetics. The addition of 3TiCl3·AlCl3 alters the controlling mechanism of the second dehydrogenation step making it change from a two-dimensional interface controlled process to a two-dimensional nucleation and growth controlled process. The microstructural investigation of the dehydrogenated 2NaBH4+MgH2 via high-resolution transmission electron microscopy (HRTEM) shows significant differences in the MgB2 morphology formed in the doped and undoped systems. The MgB2 has a needle-like structure in the sample doped with 3TiCl3·AlCl3, which is different from the plate-like MgB2 structure in the undoped sample. Moreover, nanostructured metal-based phases, such as TiB2/AlB2 particles, acting as heterogeneous nucleation sites for MgB2 are also identified for the sample doped with 3TiCl3·AlCl3. %0 journal article %@ 2079-4991 %A Jin, O.,Shang, Y.,Huang, X.,Mu, X.,Szabó, D.V.,Le, T.T.,Wagner, S.,Kübel, C.,Pistidda, C.,Pundt, A. %D 2022 %J Nanomaterials %N 11 %P 1893 %R doi:10.3390/nano12111893 %T Microstructural Study of MgB2 in the LiBH4-MgH2 Composite by Using TEM %U https://doi.org/10.3390/nano12111893 11 %X The hampered kinetics of reactive hydride composites (RHCs) in hydrogen storage and release, which limits their use for extensive applications in hydrogen storage S1and energy conversion, can be improved using additives. However, the mechanism of the kinetic restriction and the additive effect on promoting the kinetics have remained unclear. These uncertainties are addressed by utilizing versatile transmission electron microscopy (TEM) on the LiBH4-MgH2 composite under the influence of the 3TiCl3·AlCl3 additives. The formation of the MgB2 phase, as the rate-limiting step, is emphatically studied. According to the observations, the heterogeneous nucleation of MgB2 relies on different nucleation centers (Mg or TiB2 and AlB2). The varied nucleation and growth of MgB2 are related to the in-plane strain energy density at the interface, resulting from the atomic misfit between MgB2 and its nucleation centers. This leads to distinct MgB2 morphologies (bars and platelets) and different performances in the dehydrogenation kinetics of LiBH4-MgH2. It was found that the formation of numerous MgB2 platelets is regarded as the origin of the kinetic improvement. Therefore, to promote dehydrogenation kinetics in comparable RHC systems for hydrogen storage, it is suggested to select additives delivering a small atomic misfit. View Full-Text %0 journal article %@ 2516-1083 %A Dornheim, M.,Baetcke, L.,Akiba, E.,Ares, J.,Autrey, T.,Barale, J.,Baricco, M.,Brooks, K.,Chalkiadakis, N.,Charbonnier, V.,Christensen, S.,Bellosta von Colbe, J.,Costamagna, M.,Dematteis, E.,Fernández, J.,Gennett, T.,Grant, D.,Heo, T.,Hirscher, M.,Hurst, K.,Lototskyy, M.,Metz, O.,Rizzi, P.,Sakaki, K.,Sartori, S.,Stamatakis, E.,Stuart, A.,Stubos, A.,Walker, G.,Webb, C.,Wood, B.,Yartys, V.,Zoulias, E. %D 2022 %J Progress in Energy %N 4 %P 042005 %R doi:10.1088/2516-1083/ac7cb7 %T Research and development of hydrogen carrier based solutions for hydrogen compression and storage %U https://doi.org/10.1088/2516-1083/ac7cb7 4 %X Recently, the industrial and public interest in hydrogen technologies has strongly risen, since hydrogen is the ideal means for medium to long term energy storage, transport and usage in combination with renewable and green energy supply. Therefore, in a future energy system the production, storage and usage of green hydrogen is a key technology. Hydrogen is and will in future be even more used for industrial production processes as reduction agent or for the production of synthetic hydrocarbons, especially in the chemical industry and refineries. Under certain conditions material based systems for hydrogen storage and compression offer advantages over the classical systems based on gaseous or liquid hydrogen. This includes in particular lower maintenance costs, higher reliability and safety. Hydrogen storage is possible at pressures and temperatures much closer to ambient conditions. Hydrogen compression is possible without any moving parts and only by using waste heat. In this paper, the newest developments of hydrogen carriers for storage and compression are summarized. In addition, an overview of the different research activities in this field are given. %0 journal article %@ 0034-6748 %A Gleißner, R.,Beck, E.E.,Chung, S.,Semione, G.D.L.,Mukharamova, N.,Gizer, G.,Pistidda, C.,Renner, D.,Noei, H.,Vonk, V.,Stierle, A. %D 2022 %J Review of Scientific Instruments %N 7 %P 073902 %R doi:10.1063/5.0098893 %T Operando reaction cell for high energy surface sensitive x-ray diffraction and reflectometry %U https://doi.org/10.1063/5.0098893 7 %X A proof of concept is shown for the design of a high pressure heterogeneous catalysis reaction cell suitable for surface sensitive x-ray diffraction and x-ray reflectometry over planar samples using high energy synchrotron radiation in combination with mass spectrometry. This design enables measurements in a pressure range from several tens to hundreds of bars for surface investigations under realistic industrial conditions in heterogeneous catalysis or gaseous corrosion studies. %0 journal article %@ 2516-1083 %A Pasquini, L.,Sakaki, K.,Akiba, E.,Allendorf, M.D.,Alvares, E.,Ares, J.R.,Babai, D.,Baricco, M.,Bellosta Von Colbe, J.,Bereznitsky, M.,Buckley, C.E.,Cho, Y.W.,Cuevas, F.,De Rango, P.,Dematteis, E.M.,Denys, R.V.,Dornheim, M.,Fernández, J.F.,Hariyadi, A.,Hauback, B.C.,Heo, T.W.,Hirscher, M.,Humphries, T.D.,Huot, J.,Jacob, I.,Jensen, T.R.,Jerabek, P.,Kang, S.Y.,Keilbart, N.,Kim, H.,Latroche, M.,Leardini, F.,Li, H.,Ling, S.,Lototskyy, M.V.,Mullen, R.,Orimo, S.-I.,Paskevicius, M.,Pistidda, C.,Polanski, M.,Puszkiel, J.,Rabkin, E.,Sahlberg, M.,Sartori, S.,Santhosh, A.,Sato, T.,Shneck, R.Z.,Sørby, M.H.,Shang, Y.,Stavila, V.,Suh, J.-Y.,Suwarno, S.,Thi Thu, L.,Wan, L.F.,Webb, C.J.,Witman, M.,Wan, C.,Wood, B.C.,Yartys, V.A. %D 2022 %J Progress in Energy %N 3 %P 032007 %R doi:10.1088/2516-1083/ac7190 %T Magnesium- and intermetallic alloys-based hydrides for energy storage: modelling, synthesis and properties %U https://doi.org/10.1088/2516-1083/ac7190 3 %X Hydrides based on magnesium and intermetallic compounds provide a viable solution to the challenge of energy storage from renewable sources, thanks to their ability to absorb and desorb hydrogen in a reversible way with a proper tuning of pressure and temperature conditions. Therefore, they are expected to play an important role in the clean energy transition and in the deployment of hydrogen as an efficient energy vector. This review, by experts of Task 40 'Energy Storage and Conversion based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency, reports on the latest activities of the working group 'Magnesium- and Intermetallic alloys-based Hydrides for Energy Storage'. The following topics are covered by the review: multiscale modelling of hydrides and hydrogen sorption mechanisms; synthesis and processing techniques; catalysts for hydrogen sorption in Mg; Mg-based nanostructures and new compounds; hydrides based on intermetallic TiFe alloys, high entropy alloys, Laves phases, and Pd-containing alloys. Finally, an outlook is presented on current worldwide investments and future research directions for hydrogen-based energy storage. %0 journal article %@ 2516-1083 %A Dematteis, E.M.,Amdisen, M.B.,Autrey, T.,Barale, J.,Bowden, M.E.,Buckley, C.E.,Cho, Y.W.,Deledda, S.,Dornheim, M.,De Jongh, P.,Grinderslev, J.B.,Gizer, G.,Gulino, V.,Hauback, B.C.,Heere, M.,Heo, T.W.,Humphries, T.D.,Jensen, T.R.,Kang, S.Y.,Lee, Y.-S.,Li, H.-W.,Li, S.,Møller, K.T.,Ngene, P.,Orimo, S.-I.,Paskevicius, M.,Polanski, M.,Takagi, S.,Wan, L.,Wood, B.C.,Hirscher, M.,Baricco, M. %D 2022 %J Progress in Energy %N 3 %P 032009 %R doi:10.1088/2516-1083/ac7499 %T Hydrogen storage in complex hydrides: past activities and new trends %U https://doi.org/10.1088/2516-1083/ac7499 3 %X Intense literature and research efforts have focussed on the exploration of complex hydrides for energy storage applications over the past decades. A focus was dedicated to the determination of their thermodynamic and hydrogen storage properties, due to their high gravimetric and volumetric hydrogen storage capacities, but their application has been limited because of harsh working conditions for reversible hydrogen release and uptake. The present review aims at appraising the recent advances on different complex hydride systems, coming from the proficient collaborative activities in the past years from the research groups led by the experts of the Task 40 'Energy Storage and Conversion Based on Hydrogen' of the Hydrogen Technology Collaboration Programme of the International Energy Agency. An overview of materials design, synthesis, tailoring and modelling approaches, hydrogen release and uptake mechanisms and thermodynamic aspects are reviewed to define new trends and suggest new possible applications for these highly tuneable materials. %0 journal article %@ 1420-3049 %A Jin, O.,Shang, Y.,Huang, X.,Szabó, D.V.,Le, T.T.,Wagner, S.,Klassen, T.,Kübel, C.,Pistidda, C.,Pundt, A. %D 2022 %J Molecules %N 20 %P 7005 %R doi:10.3390/molecules27207005 %T Transformation Kinetics of LiBH4–MgH2 for Hydrogen Storage %U https://doi.org/10.3390/molecules27207005 20 %X The reactive hydride composite (RHC) LiBH4–MgH2 is regarded as one of the most promising materials for hydrogen storage. Its extensive application is so far limited by its poor dehydrogenation kinetics, due to the hampered nucleation and growth process of MgB2. Nevertheless, the poor kinetics can be improved by additives. This work studied the growth process of MgB2 with varying contents of 3TiCl3·AlCl3 as an additive, and combined kinetic measurements, X-ray diffraction (XRD), and advanced transmission electron microscopy (TEM) to develop a structural understanding. It was found that the formation of MgB2 preferentially occurs on TiB2 nanoparticles. The major reason for this is that the elastic strain energy density can be reduced to ~4.7 × 107 J/m3 by creating an interface between MgB2 and TiB2, as opposed to ~2.9 × 108 J/m3 at the original interface between MgB2 and Mg. The kinetics of the MgB2 growth was modeled by the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation, describing the kinetics better than other kinetic models. It is suggested that the MgB2 growth rate-controlling step is changed from interface- to diffusion-controlled when the nucleation center changes from Mg to TiB2. This transition is also reflected in the change of the MgB2 morphology from bar- to platelet-like. Based on our observations, we suggest that an additive content between 2.5 and 5 mol% 3TiCl3·AlCl3 results in the best enhancement of the dehydrogenation kinetics. %0 journal article %@ 2662-4443 %A Shang, Y.,Liu, S.,Liang, Z.,Pyczak, F.,Lei, Z.,Heidenreich, T.,Schökel, A.,Kai, J.-J.,Gizer, G.,Dornheim, M.,Klassen, T.,Pistidda, C. %D 2022 %J Communications Materials %N 1 %P 101 %R doi:10.1038/s43246-022-00324-5 %T Developing sustainable FeTi alloys for hydrogen storage by recycling %U https://doi.org/10.1038/s43246-022-00324-5 1 %X Intermetallic alloys such as FeTi have attracted ever-growing attention as a safe and efficient hydrogen storage medium. However, the utilization of high-purity metals for the synthesis of such materials poses considerable concerns over the environmental sustainability of their large-scale production. Here, we report an approach for synthesizing FeTi from industrial scraps of iron (steels C45 and 316 L) and titanium (Ti alloy Grade 2) to reduce the carbon footprint associated with FeTi alloy synthesis, without compromising their hydrogen storage properties. At 50 °C and a pressure of 0 to 100 bar, the alloys obtained by using C45-Ti Grade 2 and 316L-Ti Grade 2 can absorb a maximum amount of hydrogen of 1.61 wt.% and 1.50 wt.%, respectively. Moreover, depending on the type of steel utilized, the thermodynamic properties can be modified. Our findings pave a pathway for developing high-performance, environmentally-sustainable FeTi alloys for hydrogen storage purposes using industrial metal wastes. %0 journal article %@ 2046-2069 %A Karimi, F.,Pranzas, K.,Puszkiel, J.,Castro Riglos, V.,Milanese, C.,Vainio, U.,Pistidda, C.,Gizer, G.,Klassen, T.,Schreyer, A.,Dornheim, M. %D 2021 %J RSC Advances %N 37 %P 23122-23135 %R doi:10.1039/D1RA03246A %T A comprehensive study on lithium-based reactive hydride composite (Li-RHC) as a reversible solid-state hydrogen storage system toward potential mobile applications %U https://doi.org/10.1039/D1RA03246A 37 %X Reversible solid-state hydrogen storage is one of the key technologies toward pollutant-free and sustainable energy conversion. The composite system LiBH4–MgH2 can reversibly store hydrogen with a gravimetric capacity of 13 wt%. However, its dehydrogenation/hydrogenation kinetics is extremely sluggish (∼40 h) which hinders its usage for commercial applications. In this work, the kinetics of this composite system is significantly enhanced (∼96%) by adding a small amount of NbF5. The catalytic effect of NbF5 on the dehydrogenation/hydrogenation process of LiBH4–MgH2 is systematically investigated using a broad range of experimental techniques such as in situ synchrotron radiation X-ray powder diffraction (in situ SR-XPD), X-ray absorption spectroscopy (XAS), anomalous small angle X-ray scattering (ASAXS), and ultra/small-angle neutron scattering (USANS/SANS). The obtained results are utilized to develop a model that explains the catalytic function of NbF5 in hydrogen release and uptake in the LiBH4–MgH2 composite system. %0 journal article %@ 0360-3199 %A Yartys, V.A.,Lototskyy, M.V.,Linkov, V.,Pasupathi, S.,Davids, M.W.,Tolj, I.,Radica, G.,Denys, R.V.,Eriksen, J.,Taube, K.,Bellosta von Colbe, J.,Capurso, G.,Dornheim, M.,Smith, F.,Mathebula, D.,Swanepoel, D.,Suwarno, S. %D 2021 %J International Journal of Hydrogen Energy %N 72 %P 35896-35909 %R doi:10.1016/j.ijhydene.2021.01.190 %T HYDRIDE4MOBILITY: An EU HORIZON 2020 project on hydrogen powered fuel cell utility vehicles using metal hydrides in hydrogen storage and refuelling systems %U https://doi.org/10.1016/j.ijhydene.2021.01.190 72 %X The goal of the EU Horizon 2020 RISE project 778307 “Hydrogen fuelled utility vehicles and their support systems utilising metal hydrides” (HYDRIDE4MOBILITY), is in addressing critical issues towards a commercial implementation of hydrogen powered forklifts using metal hydride (MH) based hydrogen storage and PEM fuel cells, together with the systems for their refuelling at industrial customers facilities. For these applications, high specific weight of the metallic hydrides has an added value, as it allows counterbalancing of a vehicle with no extra cost. Improving the rates of H2 charge/discharge in MH on the materials and system level, simplification of the design and reducing the system cost, together with improvement of the efficiency of system “MH store-FC”, is in the focus of this work as a joint effort of consortium uniting academic teams and industrial partners from two EU and associated countries Member States (Norway, Germany, Croatia), and two partner countries (South Africa and Indonesia).,The work within the project is focused on the validation of various efficient and cost-competitive solutions including (i) advanced MH materials for hydrogen storage and compression, (ii) advanced MH containers characterised by improved charge-discharge dynamic performance and ability to be mass produced, (iii) integrated hydrogen storage and compression/refuelling systems which are developed and tested together with PEM fuel cells during the collaborative efforts of the consortium.,This article gives an overview of HYDRIDE4MOBILITY project focused on the results generated during its first phase (2017–2019). %0 journal article %@ 0360-3199 %A Neves, A.M.,Puszkiel, J.,Capurso, G.,Bellosta von Colbe, J.M.,Milanese, C.,Dornheim, M.,Klassen, T.,Jepsen, J. %D 2021 %J International Journal of Hydrogen Energy %N 63 %P 32110-32125 %R doi:10.1016/j.ijhydene.2021.06.227 %T Modeling the kinetic behavior of the Li-RHC system for energy-hydrogen storage: (I) absorption %U https://doi.org/10.1016/j.ijhydene.2021.06.227 63 %X The Lithium–Boron Reactive Hydride Composite System (Li-RHC) (2 LiH + MgB2/2 LiBH4 + MgH2) is a high-temperature hydrogen storage material suitable for energy storage applications. Herein, a comprehensive gas-solid kinetic model for hydrogenation is developed. Based on thermodynamic measurements under absorption conditions, the system's enthalpy ΔH and entropy ΔS are determined to amount to −34 ± 2 kJ∙mol H2−1 and −70 ± 3 J∙K−1∙mol H2−1, respectively. Based on the thermodynamic behavior assessment, the kinetic measurements' conditions are set in the range between 325 °C and 412 °C, as well as between 15 bar and 50 bar. The kinetic analysis shows that the hydrogenation rate-limiting-step is related to a one-dimensional interface-controlled reaction with a driving-force-corrected apparent activation energy of 146 ± 3 kJ∙mol H2−1. Applying the kinetic model, the dependence of the reaction rate constant as a function of pressure and temperature is calculated, allowing the design of optimized hydrogen/energy storage vessels via finite element method (FEM) simulations. %0 journal article %@ 1438-1656 %A Karimi, F.,Börris, S.,Pranzas, P.,Metz, O.,Hoell, A.,Gizer, G.,Puszkiel, J.,Riglos, M.,Pistidda, C.,Dornheim, M.,Klassen, T.,Schreyer, A. %D 2021 %J Advanced Engineering Materials %N 11 %P 2100294 %R doi:10.1002/adem.202100294 %T Characterization of LiBH4–MgH2 Reactive Hydride Composite System with Scattering and Imaging Methods Using Neutron and Synchrotron Radiation %U https://doi.org/10.1002/adem.202100294 11 %X Reversible solid-state hydrogen storage in metal hydrides is a key technology for pollution-free energy conversion systems. Herein, the LiBH2–MgH2 composite system with and without ScCl3 additive is investigated using synchrotron- and neutron-radiation-based probing methods that can be applied to characterize such lightweight metal–hydrogen systems from nanoscopic levels up to macroscopic scale. Combining the results of neutron- and photon-based methods allows a complementary insight into reaction paths and mechanisms, complex interactions between the hydride matrix and additive, hydrogen distribution, material transport, structural changes, and phase separation in the hydride matrix. The gained knowledge is of great importance for development and optimization of such novel metal-hydride-based hydrogen storage systems with respect to future applications. %0 journal article %@ 1438-1656 %A Aslan, N.,Gizer, G.,Pistidda, C.,Dornheim, M.,Müller, M.,Busch, S.,Lohstroh, W. %D 2021 %J Advanced Engineering Materials %N 11 %P 2100620 %R doi:10.1002/adem.202100620 %T High Hydrogen Mobility in an Amide–Borohydride Compound Studied by Quasielastic Neutron Scattering %U https://doi.org/10.1002/adem.202100620 11 %X The hydrogen storage performance of reactive hydride composite Mg(NH2)2+2LiH can be significantly improved by the addition of LiBH4 and the subsequent formation of an amide–borohydride compound Li4(BH4)(NH2)3 during hydrogen release. Herein, an investigation into the structure and anion motions of Li4(BH4)(NH2)3 using synchrotron radiation powder X-ray diffraction (SR-PXD; 295–573 K) and quasielastic neutron scattering (QENS; 297–514 K) is described. The highest temperature studied with QENS (514 K) is above the melting point of Li4(BH4)(NH2)3. The neutron measurements confirm a long-range diffusive motion of hydrogen-containing species with the diffusion coefficient 𝐷≈10−6 cm2 s−1. Interestingly, this value is comparable to that of Li+ diffusion inferred from conductivity measurements. SR-PXD confirms the recrystallization of Li4(BH4)(NH2)3 from the melt into the α-phase upon cooling. At temperatures below 514 K, localized rotational motions are observed that are attributed to (BH4)− tetrahedra units mainly undergoing rotations around the 𝐶3 axes. The activation energy for this thermally activated process is found to be 𝐸a=15.5±0.9 and 17.4±0.9 kJ mol−1 respectively for the two instrumental resolutions utilized in the QENS measurements, corresponding to observation times of 55 and 14 ps. %0 journal article %@ 0360-3199 %A Le, T.,Pistidda, C.,Nguyen, V.,Singh, P.,Raizada, P.,Klassen, T.,Dornheim, M. %D 2021 %J International Journal of Hydrogen Energy %N 46 %P 23723-23736 %R doi:10.1016/j.ijhydene.2021.04.150 %T Nanoconfinement effects on hydrogen storage properties of MgH2 and LiBH4 %U https://doi.org/10.1016/j.ijhydene.2021.04.150 46 %X To find a solution to efficiently exploit renewable energy sources is a key step to achieve complete independence from fossil fuel energy sources. Hydrogen is considered by many as a suitable energy vector for efficiently exploiting intermittent and unevenly distributed renewable energy sources. However, although the production of hydrogen from renewable energy sources is technically feasible, the storage of large quantities of hydrogen is challenging. Comparing to conventional compressed and cryogenic hydrogen storage, the solid-state storage of hydrogen shows many advantages in terms of safety and volumetric energy density. Among the materials available to store hydrogen, metal hydrides and complex metal hydrides have been extensively investigated due to their appealing hydrogen storage properties. Among several potentials candidates, magnesium hydride (MgH2) and lithium borohydride (LiBH4) have been widely recognized as promising solid-state hydrogen storage materials. However, before considering these hydrides ready for real-scale applications, the issue of their high thermodynamic stability and of their poor hydrogenation/dehydrogenation kinetics must be solved. An approach to modify the hydrogen storage properties of these hydrides is nanoconfinement. This review summarizes and discusses recent findings on the use of porous scaffolds as nanostructured tools for improving the thermodynamics and kinetics of MgH2 and LiBH4. %0 journal article %@ 2515-7655 %A Pistidda, C.,Santhosh, A.,Jerabek, P.,Shang, Y.,Girella, A.,Milanese, C.,Dore, M.,Garroni, S.,Bordignon, S.,Chierotti, M.R.,Klassen, T.,Dornheim, M. %D 2021 %J JPhys Energy %N 4 %P 044001 %R doi:10.1088/2515-7655/abf81b %T Hydrogenation via a low energy mechanochemical approach: the MgB2 case %U https://doi.org/10.1088/2515-7655/abf81b 4 %X This work aims at investigating the effect that the energy transferred during particle collisions in a milling process entails on solid-gas reactions. For this purpose, the synthesis of Mg(BH4)2 from MgB2 in a pressurized hydrogen atmosphere was chosen as a model reaction. MgB2 was milled under a broad set of milling parameters (i.e. milling times and rotation regimes) and the obtained product thoroughly characterized. By proving the partial formation of Mg(BH4)2, the results of this investigation indicate that the energy transferred to the powder bed by the powder particles during milling is not negligible, in particular when the milling process is protracted for a long period. %0 journal article %@ 1996-1073 %A Le, T.-T.,Pistidda, C.,Puszkiel, J.,Riglos, M.V.C.,Dreistadt, D.M.,Klassen, T.,Dornheim, M. %D 2021 %J Energies %N 23 %P 7853 %R doi:10.3390/en14237853 %T Enhanced Hydrogen Storage Properties of Li-RHC System with In-House Synthesized AlTi3 Nanoparticles %U https://doi.org/10.3390/en14237853 23 %X In recent years, the use of selected additives for improving the kinetic behavior of the system 2LiH + MgB2 (Li-RHC) has been investigated. As a result, it has been reported that some additives (e.g., 3TiCl3·AlCl3), by reacting with the Li-RHC components, form nanostructured phases (e.g., AlTi3) possessing peculiar microstructural properties capable of enhancing the system’s kinetic behavior. The effect of in-house-produced AlTi3 nanoparticles on the hydrogenation/dehydrogenation kinetics of the 2LiH + MgB2 (Li-RHC) system is explored in this work, with the aim of reaching high hydrogen storage performance. Experimental results show that the AlTi3 nanoparticles significantly improve the reaction rate of the Li-RHC system, mainly for the dehydrogenation process. The observed improvement is most likely due to the similar structural properties between AlTi3 and MgB2 phases which provide an energetically favored path for the nucleation of MgB2. In comparison with the pristine material, the Li-RHC doped with AlTi3 nanoparticles has about a nine times faster dehydrogenation rate. The results obtained from the kinetic modeling indicate a change in the Li-RHC hydrogenation reaction mechanism in the presence of AlTi3 nanoparticles. %0 journal article %@ 2213-9567 %A Shang, Y.,Pistidda, C.,Gizer, G.,Klassen, T.,Dornheim, M. %D 2021 %J Journal of Magnesium and Alloys %N 6 %P 1837-1860 %R doi:10.1016/j.jma.2021.06.007 %T Mg-based materials for hydrogen storage %U https://doi.org/10.1016/j.jma.2021.06.007 6 %X Over the last decade's magnesium and magnesium based compounds have been intensively investigated as potential hydrogen storage as well as thermal energy storage materials due to their abundance and availability as well as their extraordinary high gravimetric and volumetric storage densities. This review work provides a broad overview of the most appealing systems and of their hydrogenation/dehydrogenation properties. Special emphasis is placed on reviewing the efforts made by the scientific community in improving the material's thermodynamic and kinetic properties while maintaining a high hydrogen storage capacity. %0 journal article %@ 0360-3199 %A Wang, J.,Lei, G.,Pistidda, C.,He, T.,Cao, H.,Dornheim, M.,Chen, P. %D 2021 %J International Journal of Hydrogen Energy %N 80 %P 40196-40202 %R doi:10.1016/j.ijhydene.2021.09.216 %T Hydrogen storage properties and reaction mechanisms of K2Mn(NH2)4–8LiH system %U https://doi.org/10.1016/j.ijhydene.2021.09.216 80 %X Hydrogen storage properties of K2Mn(NH2)4–8LiH were investigated by considering its de/re-hydrogenation properties and reaction mechanisms. Experimental results show that the dehydrogenated K2Mn(NH2)4–8LiH can be almost re-hydrogenated completely at 230 °C and 50 bar of H2 with a hydrogenation rate more than 1.0 wt%/min. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and FTIR investigations reveal that during ball milling K2Mn(NH2)4 reacts with LiH to form LiNH2 and K–Mn-species1 which is probably a K–Mn-containing hydride. The ball milled sample releases hydrogen in a multi-step reaction with the formation of K3MnH5 and K–Mn-species2 as intermediates and Li2NH, Mn3N2 and MnN as final products. The full hydrogenated products are LiH, LiNH2, and K–Mn-species2. The K–Mn-species2 may play a critical role for the fast hydrogeneration. This work indicates that transition metal contained amide-hydride composite holds potentials for hydrogen storage. %0 journal article %@ 2673-4141 %A Pistidda, C. %D 2021 %J Hydrogen %N 4 %P 428-443 %R doi:10.3390/hydrogen2040024 %T Solid-State Hydrogen Storage for a Decarbonized Society %U https://doi.org/10.3390/hydrogen2040024 4 %X Humanity is confronted with one of the most significant challenges in its history. The excessive use of fossil fuel energy sources is causing extreme climate change, which threatens our way of life and poses huge social and technological problems. It is imperative to look for alternate energy sources that can replace environmentally destructive fossil fuels. In this scenario, hydrogen is seen as a potential energy vector capable of enabling the better and synergic exploitation of renewable energy sources. A brief review of the use of hydrogen as a tool for decarbonizing our society is given in this work. Special emphasis is placed on the possibility of storing hydrogen in solid-state form (in hydride species), on the potential fields of application of solid-state hydrogen storage, and on the technological challenges solid-state hydrogen storage faces. A potential approach to reduce the carbon footprint of hydrogen storage materials is presented in the concluding section of this paper. %0 journal article %@ 0360-3199 %A Thiangviriya, S.,Plerdsranoy, P.,Hagenah, A.,Le, T.T.,Kidkhunthod, P.,Utke, O.,Dornheim, M.,Klassen, T.,Pistidda, C.,Utke, R. %D 2021 %J International Journal of Hydrogen Energy %N 63 %P 32099-32109 %R doi:10.1016/j.ijhydene.2021.06.206 %T Effects of Ni-loading contents on dehydrogenation kinetics and reversibility of Mg2FeH6 %U https://doi.org/10.1016/j.ijhydene.2021.06.206 63 %X Although Mg2FeH6 has drawn significant attention for storing hydrogen, its sluggish kinetics during hydrogenation and poor reversibility hinder practical uses. In this work, the replacement of Fe atoms in Mg2FeH6 with Ni atoms is attempted and the material properties are investigated. A detailed study of the de/rehydrogenation kinetics and reaction mechanisms of the Ni-doped Mg2FeH6 is carried out. The effects of Ni-loading contents on kinetic properties and behaviors as well as reversibility and reaction pathways are characterized. In addition, the crystal structure of a new Ni-substituted Mg2FeH6 phase is confirmed. %0 journal article %@ 2045-2322 %A Gizer, G.,Puszkiel, J.,Riglos, M.,Pistidda, C.,Ramallo-López, J.,Mizrahi, M.,Santoru, A.,Gemming, T.,Tseng, J.,Klassen, T.,Dornheim, M. %D 2020 %J Scientific Reports %N %P 8 %R doi:10.1038/s41598-019-55770-y %T Improved kinetic behaviour of Mg(NH2)2-2LiH doped with nanostructured K-modified-LixTiyOz for hydrogen storage %U https://doi.org/10.1038/s41598-019-55770-y %X The system Mg(NH2)2 + 2LiH is considered as an interesting solid-state hydrogen storage material owing to its low thermodynamic stability of ca. 40 kJ/mol H2 and high gravimetric hydrogen capacity of 5.6 wt.%. However, high kinetic barriers lead to slow absorption/desorption rates even at relatively high temperatures (>180 °C). In this work, we investigate the effects of the addition of K-modified LixTiyOz on the absorption/desorption behaviour of the Mg(NH2)2 + 2LiH system. In comparison with the pristine Mg(NH2)2 + 2LiH, the system containing a tiny amount of nanostructured K-modified LixTiyOz shows enhanced absorption/desorption behaviour. The doped material presents a sensibly reduced (∼30 °C) desorption onset temperature, notably shorter hydrogen absorption/desorption times and reversible hydrogen capacity of about 3 wt.% H2 upon cycling. Studies on the absorption/desorption processes and micro/nanostructural characterizations of the Mg(NH2)2 + 2LiH + K-modified LixTiyOz system hint to the fact that the presence of in situ formed nanostructure K2TiO3 is the main responsible for the observed improved kinetic behaviour. %0 journal article %@ 1023-8166 %A Aslan, N.,Horstmann, C.,Metz, O.,Kotlyar, O.,Dornheim, M.,Pistidda, C.,Busch, S.,Lohstroh, W.,Müller, M.,Pranzas, K. %D 2020 %J Journal of Neutron Research %N 3 - 4 %P 125-135 %R doi:10.3233/JNR-190116 %T High-pressure cell for in situ neutron studies of hydrogen storage materials %U https://doi.org/10.3233/JNR-190116 3 - 4 %X A high- pressure cell for neutron experiments was developed at Helmholtz-Zentrum Geesthacht (HZG). This cell is designed for the investigation of hydrogen storage materials at pressures up to 700 bar and temperatures up to 500°C. The idea is to have a prototype cell for different neutron scattering methods (diffraction, time- of-flight spectroscopy and small-angle neutron scattering). In this work, we discuss the development and the current state of the high- pressure cell. Furthermore, the deployment of the cell for in situ small-angle neutron scattering measurements on 6Mg(NH2 )2 + 9LiH + LiBH4 (6:9:1) at the instrument SANS-1 at Heinz Maier-Leibnitz Zentrum (MLZ) is demonstrated. %0 journal article %@ 1996-1944 %A Le, T.-T.,Pistidda, C.,Abetz, C.,Georgopanos, P.,Garroni, S.,Capurso, G.,Milanese, C.,Puszkiel, J.,Dornheim, M.,Abetz, V.,Klassen, T. %D 2020 %J Materials %N 4 %P 991 %R doi:10.3390/ma13040991 %T Enhanced Stability of Li-RHC Embedded in an Adaptive TPX™ Polymer Scaffold %U https://doi.org/10.3390/ma13040991 4 %X In this work, the possibility of creating a polymer-based adaptive scaffold for improving the hydrogen storage properties of the system 2LiH+MgB2+7.5(3TiCl3·AlCl3) was studied. Because of its chemical stability toward the hydrogen storage material, poly(4-methyl-1-pentene) or in-short TPXTM was chosen as the candidate for the scaffolding structure. The composite system was obtained after ball milling of 2LiH+MgB2+7.5(3TiCl3·AlCl3) and a solution of TPXTM in cyclohexane. The investigations carried out over the span of ten hydrogenation/de-hydrogenation cycles indicate that the material containing TPXTM possesses a higher degree of hydrogen storage stability. %0 journal article %@ 2045-2322 %A Heere, M.,Hansen, A.-L.,Payandeh, S.H.,Aslan, N.,Gizer, G.,Sørby, M.H.,Hauback, B.C.,Pistidda, C.,Dornheim, M.,Lohstroh, W. %D 2020 %J Scientific Reports %N 1 %P 9080 %R doi:10.1038/s41598-020-65857-6 %T Dynamics of porous and amorphous magnesium borohydride to understand solid state Mg-ion-conductors %U https://doi.org/10.1038/s41598-020-65857-6 1 %X Rechargeable solid-state magnesium batteries are considered for high energy density storage and usage in mobile applications as well as to store energy from intermittent energy sources, triggering intense research for suitable electrode and electrolyte materials. Recently, magnesium borohydride, Mg(BH4)2, was found to be an effective precursor for solid-state Mg-ion conductors. During the mechanochemical synthesis of these Mg-ion conductors, amorphous Mg(BH4)2 is typically formed and it was postulated that this amorphous phase promotes the conductivity. Here, electrochemical impedance spectroscopy of as-received γ-Mg(BH4)2 and ball milled, amorphous Mg(BH4)2 confirmed that the conductivity of the latter is ~2 orders of magnitude higher than in as-received γ-Mg(BH4)2 at 353 K. Pair distribution function (PDF) analysis of the local structure shows striking similarities up to a length scale of 5.1 Å, suggesting similar conduction pathways in both the crystalline and amorphous sample. Up to 12.27 Å the PDF indicates that a 3D net of interpenetrating channels might still be present in the amorphous phase although less ordered compared to the as-received γ-phase. However, quasi elastic neutron scattering experiments (QENS) were used to study the rotational mobility of the [BH4] units, revealing a much larger fraction of activated [BH4] rotations in amorphous Mg(BH4)2. These findings suggest that the conduction process in amorphous Mg(BH4)2 is supported by stronger rotational mobility, which is proposed to be the so-called “paddle-wheel” mechanism. %0 journal article %@ 0925-8388 %A Hirscher, M.,Yartys, V.A.,Baricco, M.,Bellosta von Colbe, J.,Blanchard, D.,Bowman, R.C.,Jr.,Broom, D.P.,Buckley, C.E.,Chang, F.,Chen, P.,Cho, Y.W.,Crivello, J.-C.,Cuevas, F.,David, W.I.F.,de Jongh, P.E.,Denys, R.V.,Dornheim, M.,Felderhoff, M.,Filinchuk, Y.,Froudakis, G.E.,Grant, D.M.,Gray, E.M.,Hauback, B.C.,He, T.,Humphries, T.D.,Jensen, T.R.,Kim, S.,Kojima, Y.,Latroche, M.,Li, H.-W.,Lototskyy, M.V.,Makepeace, J.W.,Møller, K.T.,Naheed, L.,Ngene, P.,Noréus, D.,Nygård, M.M.,Orimo, S.-I.,Paskevicius, M.,Pasquini, L.,Ravnsbæk, D.B.,Veronica Sofianos, M.,Udovic, T.J.,Vegge, T.,Walker, G.S.,Webb, C.J.,Weidenthaler, C.,Zlotea, C. %D 2020 %J Journal of Alloys and Compounds %N %P 153548 %R doi:10.1016/j.jallcom.2019.153548 %T Materials for hydrogen-based energy storage – past, recent progress and future outlook %U https://doi.org/10.1016/j.jallcom.2019.153548 %X Globally, the accelerating use of renewable energy sources, enabled by increased efficiencies and reduced costs, and driven by the need to mitigate the effects of climate change, has significantly increased research in the areas of renewable energy production, storage, distribution and end-use. Central to this discussion is the use of hydrogen, as a clean, efficient energy vector for energy storage. This review, by experts of Task 32, “Hydrogen-based Energy Storage” of the International Energy Agency, Hydrogen TCP, reports on the development over the last 6 years of hydrogen storage materials, methods and techniques, including electrochemical and thermal storage systems. An overview is given on the background to the various methods, the current state of development and the future prospects. The following areas are covered; porous materials, liquid hydrogen carriers, complex hydrides, intermetallic hydrides, electrochemical storage of energy, thermal energy storage, hydrogen energy systems and an outlook is presented for future prospects and research on hydrogen-based energy storage. %0 journal article %@ 1477-9226 %A Caggiu, L.,Iacomini, A.,Pistidda, C.,Farina, V.,Senes, N.,Cao, H.,Gavini, E.,Mulas, G.,Garroni, S.,Enzo, S. %D 2020 %J Dalton Transactions %N 48 %P 17584-17593 %R doi:10.1039/d0dt03426f %T In situ synchrotron radiation investigation of V2O5–Nb2O5 metastable compounds: transformational kinetics at high temperatures with a new structural solution for the orthorhombic V4Nb20O60 phase %U https://doi.org/10.1039/d0dt03426f 48 %X Due to the considerable interest in vanadium niobium oxides as a lithium storage material, the kinetics and transformation processes of the V2O5–5Nb2O5 system have been investigated by in situ synchrotron powder X-ray diffraction. The diffraction data after the thermal treatments selected with a view on the most significant features were supplemented with specific ex situ experiments conducted using a laboratory rotating anode X-ray diffractometer. The morphological changes of the mixed powders assuming an amorphous and nanocrystalline solid solution structure as a function of the temperature were inspected by scanning electron microscopy observations. The structural solution of the powder diffraction pattern of the phase recorded in situ at a temperature of about 700 °C was compatible with an orthorhombic crystal structure with the space group Amm2. The obtained lattice parameters for this structure were a = 3.965 Å; b = 17.395 Å, c = 17.742 Å, and the cell composition was V4Nb20O60, Pearson symbol oA84, and density = 4.10 g cm−3. In this structure, while the niobium atoms may be four-, five-, and six-fold coordinated by oxygen atoms, the vanadium atoms were six-fold or seven-fold coordinated. At the temperature of 800 °C and just above, the selected 1 : 2 and 1 : 3 V2O5–Nb2O5 compositions, respectively, returned mostly a tetragonal VNb9O25 phase, in line with earlier observations conducted for determination of the stability phase diagram of such quasi-binary systems. %0 journal article %@ 0360-3199 %A Bellosta von Colbe, J.,Ares, J.-R.,Barale, J.,Baricco, M.,Buckley, C.,Capurso, G.,Gallandat, N.,Grant, D.M.,Guzik, M.N.,Jacob, I.,Jensen, E.H.,Jensen, T.,Jepsen, J.,Klassen, T.,Lototskyy, M.V.,Manickam, K.,Montone, A.,Puszkiel, J.,Sartori, S.,Sheppard, D.A.,Stuart, A.,Walker, G.,Webb, C.J.,Yang, H.,Yartys, V.,Zuettel, A.,Dornheim, M. %D 2019 %J International Journal of Hydrogen Energy %N 15 %P 7780 %R doi:10.1016/j.ijhydene.2019.01.104 %T Application of hydrides in hydrogen storage and compression: Achievements, outlook and perspectives %U https://doi.org/10.1016/j.ijhydene.2019.01.104 15 %X Metal hydrides are known as a potential efficient, low-risk option for high-density hydrogen storage since the late 1970s. In this paper, the present status and the future perspectives of the use of metal hydrides for hydrogen storage are discussed. Since the early 1990s, interstitial metal hydrides are known as base materials for Ni – metal hydride rechargeable batteries. For hydrogen storage, metal hydride systems have been developed in the 2010s [1] for use in emergency or backup power units, i. e. for stationary applications.,With the development and completion of the first submarines of the U212 A series by HDW (now Thyssen Krupp Marine Systems) in 2003 and its export class U214 in 2004, the use of metal hydrides for hydrogen storage in mobile applications has been established, with new application fields coming into focus.,In the last decades, a huge number of new intermetallic and partially covalent hydrogen absorbing compounds has been identified and partly more, partly less extensively characterized.,In addition, based on the thermodynamic properties of metal hydrides, this class of materials gives the opportunity to develop a new hydrogen compression technology. They allow the direct conversion from thermal energy into the compression of hydrogen gas without the need of any moving parts. Such compressors have been developed and are nowadays commercially available for pressures up to 200 bar. Metal hydride based compressors for higher pressures are under development. Moreover, storage systems consisting of the combination of metal hydrides and high-pressure vessels have been proposed as a realistic solution for on-board hydrogen storage on fuel cell vehicles.,In the frame of the “Hydrogen Storage Systems for Mobile and Stationary Applications” Group in the International Energy Agency (IEA) Hydrogen Task 32 “Hydrogen-based energy storage”, different compounds have been and will be scaled-up in the near future and tested in the range of 500 g to several hundred kg for use in hydrogen storage applications. %0 journal article %@ 2075-4701 %A Jepsen, J.,Capurso, G.,Puszkiel, J.,Busch, N.,Werner, T.,Milanese, C.,Girella, A.,Bellosta von Colbe, J.,Dornheim, M.,Klassen, T. %D 2019 %J Metals %N 3 %P 349 %R doi:10.3390/met9030349 %T Effect of the Process Parameters on the Energy Transfer during the Synthesis of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage %U https://doi.org/10.3390/met9030349 3 %X Several different milling parameters (additive content, rotation velocity, ball-to-powder ratio, degree of filling, and time) affect the hydrogen absorption and desorption properties of a reactive hydride composite (RHC). In this paper, these effects were thoroughly tested and analyzed. The milling process investigated in such detail was performed on the 2LiH-MgB2 system doped with TiCl3. Applying an upgraded empirical model, the transfer of energy to the material during the milling process was determined. In this way, it is possible to compare the obtained experimental results with those from processes at different scales. In addition, the different milling parameters were evaluated independently according to their individual effect on the transferred energy. Their influence on the reaction kinetics and hydrogen capacity was discussed and the results were correlated to characteristics like particle and crystallite size, specific surface area, presence of nucleation sites and contaminants. Finally, an optimal value for the transferred energy was determined, above which the powder characteristics do not change and therefore the RHC system properties do not further improve. %0 journal article %@ 0360-3199 %A Bellosta von Colbe, J.M.,Puszkiel, J.,Capurso, G.,Franz, A.,Benz, H.U.,Zoz, H.,Klassen, T.,Dornheim, M. %D 2019 %J International Journal of Hydrogen Energy %N 55 %P 29282-29290 %R doi:10.1016/j.ijhydene.2019.01.174 %T Scale-up of milling in a 100 L device for processing of TiFeMn alloy for hydrogen storage applications: Procedure and characterization %U https://doi.org/10.1016/j.ijhydene.2019.01.174 55 %X In this work, the mechanical milling of a FeTiMn alloy for hydrogen storage purposes was performed in an industrial milling device. The TiFe hydride is interesting from the technological standpoint because of the abundance and the low cost of its constituent elements Ti and Fe, as well as its high volumetric hydrogen capacity. However, TiFe is difficult to activate, usually requiring a thermal treatment above 400 °C. A TiFeMn alloy milled for just 10 min in a 100 L industrial milling device showed excellent hydrogen storage properties without any thermal treatment. The as-milled TiFeMn alloy did not need any activation procedure and showed fast kinetic behavior and good cycling stability. Microstructural and morphological characterization of the as-received and as-milled TiFeMn alloys revealed that the material presents reduced particle and crystallite sizes, even after such short time of milling. The refined microstructure of the as-milled TiFeMn is deemed to account for the improved hydrogen absorption-desorption properties. %0 journal article %@ 0360-3199 %A Gizer, G.,Puszkiel, J.,Cao, H.,Pistidda, C.,Le, T.,Dornheim, M.,Klassen, T. %D 2019 %J International Journal of Hydrogen Energy %N 23 %P 11920-11929 %R doi:10.1016/j.ijhydene.2019.03.133 %T Tuning the reaction mechanism and hydrogenation/dehydrogenation properties of 6Mg(NH2)2single bond9LiH system by adding LiBH4 %U https://doi.org/10.1016/j.ijhydene.2019.03.133 23 %X The hydrogen storage properties of 6Mg(NH2)2single bond9LiH-x(LiBH4) (x = 0, 0.5, 1, 2) system and the role of LiBH4 on the kinetic behaviour and the dehydrogenation/hydrogenation reaction mechanism were herein systematically investigated. Among the studied compositions, 6Mg(NH2)2single bond9LiHsingle bond2LiBH4 showed the best hydrogen storage properties. The presence of 2 mol of LiBH4 improved the thermal behaviour of the 6Mg(NH2)2single bond9LiH by lowering the dehydrogenation peak temperature nearly 25 °C and by reducing the apparent dehydrogenation activation energy of about 40 kJ/mol. Furthermore, this material exhibited fast dehydrogenation (10 min) and hydrogenation kinetics (3 min) and excellent cycling stability with a reversible hydrogen capacity of 3.5 wt % at isothermal 180 °C. Investigations on the reaction pathway indicated that the observed superior kinetic behaviour likely related to the formation of Li4(BH4)(NH2)3. Studies on the rate-limiting steps hinted that the sluggish kinetic behaviour of the 6Mg(NH2)2single bond9LiH pristine material are attributed to an interface-controlled mechanism. On the contrary, LiBH4-containing samples show a diffusion-controlled mechanism. During the first dehydrogenation reaction, the possible formation of Li4(BH4)(NH2)3 accelerates the reaction rates at the interface. Upon hydrogenation, this ‘liquid like’ of Li4(BH4)(NH2)3 phase assists the diffusion of small ions into the interfaces of the amide-hydride matrix. %0 journal article %@ 1996-1073 %A Gizer, G.,Cao, H.,Puszkiel, J.,Pistidda, C.,Santoru, A.,Zhang, W.,He, T.,Chen, P.,Klassen, T.,Dornheim, M. %D 2019 %J Energies %N 14 %P 2779 %R doi:10.3390/en12142779 %T Enhancement Effect of Bimetallic Amide K2Mn(NH2)4 and In-Situ Formed KH and Mn4N on the Dehydrogenation/Hydrogenation Properties of Li–Mg–N–H System %U https://doi.org/10.3390/en12142779 14 %X In this work, we investigated the influence of the K2Mn(NH2)4 additive on the hydrogen sorption properties of the Mg(NH2)2 + 2LiH (Li–Mg–N–H) system. The addition of 5 mol% of K2Mn(NH2)4 to the Li–Mg–N–H system leads to a decrease of the dehydrogenation peak temperature from 200 °C to 172 °C compared to the pristine sample. This sample exhibits a constant hydrogen storage capacity of 4.2 wt.% over 25 dehydrogenation/rehydrogenation cycles. Besides that, the in-situ synchrotron powder X-ray diffraction analysis performed on the as prepared Mg(NH2)2 + 2LiH containing K2Mn(NH2)4 indicates the presence of Mn4N. However, no crystalline K-containing phases were detected. Upon dehydrogenation, the formation of KH is observed. The presence of KH and Mn4N positively influences the hydrogen sorption properties of this system, especially at the later stage of rehydrogenation. Under the applied conditions, hydrogenation of the last 1 wt.% takes place in only 2 min. This feature is preserved in the following three cycles. %0 journal article %@ 2075-4701 %A Le, T.,Pistidda, C.,Puszkiel, J.,Milanese, C.,Garroni, S.,Emmler, T.,Capurso, G.,Gizer, G.,Klassen, T.,Dornheim, M. %D 2019 %J Metals %N 10 %P 1061 %R doi:10.3390/met9101061 %T Efficient Synthesis of Alkali Borohydrides from Mechanochemical Reduction of Borates Using Magnesium–Aluminum-Based Waste %U https://doi.org/10.3390/met9101061 10 %X Lithium borohydride (LiBH4) and sodium borohydride (NaBH4) were synthesized via mechanical milling of LiBO2, and NaBO2 with Mg–Al-based waste under controlled gaseous atmosphere conditions. Following this approach, the results herein presented indicate that LiBH4 and NaBH4 can be formed with a high conversion yield starting from the anhydrous borates under 70 bar H2. Interestingly, NaBH4 can also be obtained with a high conversion yield by milling NaBO2·4H2O and Mg–Al-based waste under an argon atmosphere. Under optimized molar ratios of the starting materials and milling parameters, NaBH4 and LiBH4 were obtained with conversion ratios higher than 99.5%. Based on the collected experimental results, the influence of the milling energy and the correlation with the final yields were also discussed. %0 journal article %@ 1439-4235 %A Dematteis, E.,Pistidda, C.,Dornheim, M.,Baricco, M. %D 2019 %J ChemPhysChem %N 10 %P 1348-1359 %R doi:10.1002/cphc.201801130 %T Exploring Ternary and Quaternary Mixtures in the LiBH4-NaBH4-KBH4-Mg(BH4)2-Ca(BH4)2 System %U https://doi.org/10.1002/cphc.201801130 10 %X Binary combinations of borohydrides have been extensivly investigated evidencing the formation of eutectics, bimetallic compounds or solid solutions. In this paper, the investigation has been extended to ternary and quaternary systems in the LiBH4-NaBH4-KBH4-Mg(BH4)2-Ca(BH4)2 system. Possible interactions among borohydrides in equimolar composition has been explored by mechanochemical treatment. The obtained phases were analysed by X-ray diffraction and the thermal behaviour of the mixtures were analysed by HP-DSC and DTA, defining temperature of transitions and decomposition reactions. The release of hydrogen was detected by MS, showing the role of the presence of solid solutions and multi-cation compounds on the hydrogen desorption reactions. The presence of LiBH4 generally promotes the release of H2 at about 200 °C, while KCa(BH4)3 promotes the release in a single-step reaction at higher temperatures. %0 journal article %@ 0360-3199 %A Thiangviriya, S.,Sitthiwet, C.,Plerdsranoy, P.,Capurso, G.,Pistidda, C.,Utke, O.,Dornheim, M.,Klassen, T.,Utke, R. %D 2019 %J International Journal of Hydrogen Energy %N 29 %P 15218-15227 %R doi:10.1016/j.ijhydene.2019.04.146 %T Hydrogen sorption kinetics, hydrogen permeability, and thermal properties of compacted 2LiBH4single bondMgH2 doped with activated carbon nanofibers %U https://doi.org/10.1016/j.ijhydene.2019.04.146 29 %X To improve the packing efficiency in tank scale, hydrides have been compacted into pellet form; however, poor hydrogen permeability through the pellets results in sluggish kinetics. In this work, the hydrogen sorption properties of compacted 2LiBH4single bondMgH2 doped with 30 wt % activated carbon nanofibers (ACNF) are investigated. After doping with ACNF, onset dehydrogenation temperature of compacted 2LiBH4single bondMgH2 decreases from 350 to 300 °C and hydrogen released content enhances from 55 to 87% of the theoretical capacity. The sample containing ACNF releases hydrogen following a two-step mechanism with reversible hydrogen storage capacities up to 4.5 wt % H2 and 41.8 gH2/L, whereas the sample without ACNF shows a single-step decomposition mainly from MgH2 with only 1.8 wt % H2 and 15.4 gH2/L. Significant kinetic improvement observed in the doped system is due to the enhancement of both hydrogen permeability and heat transfer through the pellet. %0 journal article %@ 0360-3199 %A Milanese, C.,Jensen, T.,Hauback, B.,Pistidda, C.,Dornheim, M.,Yang, H.,Lombardo, L.,Züttel, A.,Filinchuk, Y.,de Jongh, P.,Buckley, C.,Dematteis, E.,Baricco, M. %D 2019 %J International Journal of Hydrogen Energy %N 15 %P 7860-7874 %R doi:10.1016/j.ijhydene.2018.11.208 %T Complex hydrides for energy storage %U https://doi.org/10.1016/j.ijhydene.2018.11.208 15 %X In the past decades, complex hydrides and complex hydrides-based materials have been thoroughly investigated as materials for energy storage, owing to their very high gravimetric and volumetric hydrogen capacities and interesting cation and hydrogen diffusion properties. Concerning hydrogen storage, the main limitations of this class of materials are the high working temperatures and pressures, the low hydrogen absorption and desorption rates and the poor cyclability. In the past years, research in this field has been focused on understanding the hydrogen release and uptake mechanism of the pristine and catalyzed materials and on the characterization of the thermodynamic aspects, in order to rationally choose the composition and the stoichiometry of the systems in terms of hydrogen active phases and catalysts/destabilizing agents. Moreover, new materials have been discovered and characterized in an attempt to find systems with properties suitable for practical on-board and stationary applications. A significant part of this rich and productive activity has been performed by the research groups led by the Experts of the International Energy Agreement Task 32, often in collaborative research projects. The most recent findings of these joint activities and other noteworthy recent results in the field are reported in this paper. %0 journal article %@ 1477-9226 %A Valentoni, A.,Barra, P.,Senes, N.,Mulas, G.,Pistidda, C.,Bednarcik, J.,Torre, F.,Garroni, S.,Enzo, S. %D 2019 %J Dalton Transactions %N 29 %P 10986-10995 %R doi:10.1039/c9dt01236b %T A mechanochemical route for the synthesis of VNbO5 and its structural re-investigation using structure solution from powder diffraction data %U https://doi.org/10.1039/c9dt01236b 29 %X A new and solvent-free synthesis route has been adopted and optimized to prepare crystalline VNbO5 from the mechanochemical reaction between Nb2O5 and V2O5 as starting reagents. The substantially amorphous mixture of equimolar pentoxide V and Nb metals observed after extended mechanical treatment transforms into a crystalline powder following calcination under mild conditions at 710 K. The structure solution of the X-ray diffraction pattern using a global optimization approach, combined with Rietveld refinement, points to a space group P212121 (no. 19) different from Pnma (no. 62) previously proposed in the literature assuming it to be isostructural to VTaO5. The new space group helps to describe weak peaks that remained previously unaccounted for and allows more reliable determination of atomic fractional coordinates and interatomic distance distribution. The as-prepared VNbO5 has been tested as a dopant (5 wt%) for the purpose of solid state hydrogen storage, decreasing significantly the release of hydrogen of MgH2/Mg (620 K) and further enhancing the hydrogen sorption kinetic properties. %0 journal article %@ 1463-9076 %A Grasso, M.,Puszkiel, J.,Fernandez Albanesi, L.,Dornheim, M.,Pistidda, C.,Gennari, F. %D 2019 %J Physical Chemistry Chemical Physics %N 36 %P 19825-19834 %R doi:10.1039/c9cp03826d %T CO2 reutilization for methane production via a catalytic process promoted by hydrides %U https://doi.org/10.1039/c9cp03826d 36 %X CO2 emissions have been continuously increasing during the last half of the century with a relevant impact on the planet and are the main contributor to the greenhouse effect and global warming. The development of new technologies to mitigate these emissions poses a challenge. Herein, the recycling of CO2 to produce CH4 selectively by using Mg2FeH6 and Mg2NiH4 complex hydrides as dual conversion promoters and hydrogen sources has been demonstrated. Magnesium-based metal hydrides containing Fe and Ni catalyzed the hydrogenation of CO2 and their total conversion was obtained at 400 °C after 5 h and 10 h, respectively. The complete hydrogenation of CO2 depended on the complex hydride, H2 : CO2 mol ratio, and experimental conditions: temperature and time. For both hydrides, the activation of CO2 on the metal surface and its subsequent capture resulted in the formation of MgO. Investigations on the Mg2FeH6–CO2 system indicated that the main process occurs via the reversed water–gas shift reaction (WGSR), followed by the methanation of CO in the presence of steam. In contrast, the reduction of CO2 by the Mg-based hydride in the Mg2NiH4–CO2 system has a strong contribution to the global process. Complex metal hydrides are promising dual promoter-hydrogen sources for CO2 recycling and conversion into valuable fuels such as CH4. %0 journal article %@ 2468-6069 %A Mortalo, C.,Santoru, A.,Pistidda, C.,Rebollo, E.,Boaro, M.,Leonelli, C.,Fabrizio, M. %D 2019 %J Materials Today Energy %N %P 331-341 %R doi:10.1016/j.mtener.2019.06.004 %T Structural evolution of BaCe0.65Zr0.20Y0.15O3-δ-Ce0.85Gd0.15O2-δ composite MPEC membrane by in-situ synchrotron XRD analyses %U https://doi.org/10.1016/j.mtener.2019.06.004 %X Nowadays, dense ceramic membranes based on mixed ionic and electronic conductors are considered very promising materials for H2 separation at T > 600 °C. Among these, BaCe0.65Zr0.2Y0.15O3-δ-Ce0.85Gd0.15O2-δ (BCZ20Y15-GDC15) composite combine an acceptable H2 flux and good chemical stability under CO2- and H2S-containing atmospheres. However, a clear understanding of its crystal structure, phase stability and mechanical stability under real working conditions could not yet be obtained. In this work, its structural evolution was investigated from room temperature to 800 °C by in-situ synchrotron XRD analyses under dry and wet H2. No chemical interaction between the BCZ20Y15 and GDC15 phases occurred in the composite, thus demontrating its excellent chemical stability under operating conditions. However, some phase transitions were observed for the BCZ20Y15 phase, under both dry and wet H2: i.e., it showed an orthorhombic Imma structure from room temperature to 100 °C, trigonal R-3c up to 700 °C and cubic Pm-3m up to 800 °C. On the other hand, the GDC15 phase did not display any phase transition, remaining in a cubic Fm-3m structure under all tested conditions. Moreover, a synergistic effect of the BCZ20Y15 and GDC15 phases in the volume expansion of the composite was revealed: indeed, BCZ20Y15 and GDC15 lattice expansion rates tend to approach each other in the composite under reducing conditions. This synergistic effect is very important for the mechanical performances of BCZ20Y15-GDC15 composite. The similar expansion rate observed for BCZ20Y15 and GDC15 may reduce the strain and prevent failure of this ceramic membrane under operating conditions. %0 journal article %@ 2095-4956 %A Bergemann, N.,Pistidda, C.,Uptmoor, M.,Milanese, C.,Santoru, A.,Emmler, T.,Puszkiel, J.,Dornheim, M.,Klassen, T. %D 2019 %J Journal of Energy Chemistry %N %P 240-254 %R doi:10.1016/j.jechem.2019.03.011 %T A new mutually destabilized reactive hydride system: LiBH4–Mg2NiH4 %U https://doi.org/10.1016/j.jechem.2019.03.011 %X In this work, the hydrogen sorption properties of the LiBH4–Mg2NiH4 composite system with the molar ratio 2:2.5 were thoroughly investigated as a function of the applied temperature and hydrogen pressure. To the best of our knowledge, it has been possible to prove experimentally the mutual destabilization between LiBH4 and Mg2NiH4. A detailed account of the kinetic and thermodynamic features of the dehydrogenation process is reported here. %0 journal article %@ 0925-8388 %A Sofianos, M.V.,Chaudhary, A.-L.,Paskevicius, M.,Sheppard, D.A.,Humphries, T.D.,Dornheim, M.,Buckley, C.E. %D 2019 %J Journal of Alloys and Compounds %N %P 474-480 %R doi:10.1016/j.jallcom.2018.10.086 %T Hydrogen storage properties of eutectic metal borohydrides melt-infiltrated into porous Al scaffolds %U https://doi.org/10.1016/j.jallcom.2018.10.086 %X Porous Al scaffolds were synthesised and melt-infiltrated with various eutectic metal borohydride mixtures (0.725LiBH4-0.275KBH4, 0.68NaBH4-0.32KBH4, 0.4NaBH4-0.6 Mg(BH4)2) to simultaneously act as both a confining framework and a reactive destabilising agent for H2 release. The scaffolds were synthesised by sintering a pellet of NaAlH4/2 mol%TiCl3 at 450 °C under dynamic vacuum. During the sintering process the sodium alanate (NaAlH4) decomposed to Al metal. The vacuum applied at elevated temperature promoted the Na metal to vaporise and be extruded from the pellet. The pores of the resulting Al scaffold were created during removal of the H2 and the Na from the body of the NaAlH4/2 mol%TiCl3 pellet. According to the morphological observations carried out by a Scanning Electron Microscope (SEM), melt-infiltrated eutectic mixtures of metal borohydrides were highly dispersed into the porous scaffolds. Temperature Programmed Desorption (TPD) experiments, revealed that the melt-infiltrated samples exhibited faster H2 desorption kinetics in comparison to bulk samples, with onset temperatures (Tdes) lower than the bulk by 150–250 °C. The as-synthesised porous Al scaffolds acted as a reactive containment vessel for these eutectic mixtures that simultaneously nanoconfined and destabilised the mixtures. %0 journal article %@ 1996-1073 %A Jepsen, J.,Milanese, C.,Puszkiel, J.,Girella, A.,Schiavo, B.,Lozano, G.A.,Capurso, G.,Bellosta von Colbe, J.M.,Marini, A.,Kabelac, S.,Dornheim, M.,Klassen, T. %D 2018 %J Energies %N 5 %P 1081 %R doi:10.3390/en11051081 %T Fundamental Material Properties of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage: (I) Thermodynamic and Heat Transfer Properties %U https://doi.org/10.3390/en11051081 5 %X Thermodynamic and heat transfer properties of the 2LiBH4-MgH2 composite (Li-RHC) system are experimentally determined and studied as a basis for the design and development of hydrogen storage tanks. Besides the determination and discussion of the properties, different measurement methods are applied and compared to each other. Regarding thermodynamics, reaction enthalpy and entropy are determined by pressure-concentration-isotherms and coupled manometric-calorimetric measurements. For thermal diffusivity calculation, the specific heat capacity is measured by high-pressure differential scanning calorimetry and the effective thermal conductivity is determined by the transient plane source technique and in situ thermocell. Based on the results obtained from the thermodynamics and the assessment of the heat transfer properties, the reaction mechanism of the Li-RHC and the issues related to the scale-up for larger hydrogen storage systems are discussed in detail. %0 journal article %@ 2366-7486 %A Capurso, G.,Schiavo, B.,Jepsen, J.,Lozano, G.A.,Metz, O.,Klassen, T.,Dornheim, M. %D 2018 %J Advanced Sustainable Systems %N 6 %P 1800004 %R doi:10.1002/adsu.201800004 %T Metal Hydride‐Based Hydrogen Storage Tank Coupled with an Urban Concept Fuel Cell Vehicle: Off Board Tests %U https://doi.org/10.1002/adsu.201800004 6 %X In this work, the tests of a hydrogen storage system intended for vehicular applications, using a metal hydride as storage material, are reported. The system is designed to deliver gas to a fuel cell prototype vehicle. The room temperature hydride is an interstitial alloy, which is selected for its capacity to absorb and desorb hydrogen over an appropriate range of temperature and pressure. The static tests aim to assess whether the requirements for hydrogen release are reliably met by the tank setup. Hypothetical on‐road tests have been designed and applied. Dynamic tests allow moving from energy to power density. Solutions are adopted to face the issues of thermal management at higher‐demanding performances. Several cycles have been performed to find the ideal settings to preserve high average and peak gas flow in a realistic situation. The use of a metal hydride, to replace pressurized gas, results in improved performances, including an extended range at lower loading pressures. Decreasing the pressure in the storage system enables the advantageous possibility to reload the tank several times with commercially available cylinders. Possible future enhancements in the reduction of the total weight of the system are also considered. %0 journal article %@ 1996-1073 %A Jepsen, J.,Milanese, C.,Puszkiel, J.,Girella, A.,Schiavo, B.,Lozano, G.A.,Capurso, G.,Bellosta von Colbe, J.M.,Marini, A.,Kabelac, S.,Dornheim, M.,Klassen, T. %D 2018 %J Energies %N 5 %P 1170 %R doi:10.3390/en11051170 %T Fundamental Material Properties of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage: (II) Kinetic Properties %U https://doi.org/10.3390/en11051170 5 %X Reaction kinetic behaviour and cycling stability of the 2LiBH4–MgH2 reactive hydride composite (Li-RHC) are experimentally determined and analysed as a basis for the design and development of hydrogen storage tanks. In addition to the determination and discussion about the properties; different measurement methods are applied and compared. The activation energies for both hydrogenation and dehydrogenation are determined by the Kissinger method and via the fitting of solid-state reaction kinetic models to isothermal volumetric measurements. Furthermore, the hydrogen absorption–desorption cycling stability is assessed by titration measurements. Finally, the kinetic behaviour and the reversible hydrogen storage capacity of the Li-RHC are discussed. %0 journal article %@ 2468-6069 %A Cao, H.,Georgopanos, P.,Capurso, G.,Pistidda, C.,Weigelt, F.,Chaudhary, A.-L.,Filiz, V.,Tseng, J.-C.,Wharmby, M.T.,Dornheim, M.,Abetz, V.,Klassen, T. %D 2018 %J Materials Today : Energy %N %P 98-107 %R doi:10.1016/j.mtener.2018.08.008 %T Air-stable metal hydride-polymer composites of Mg(NH2)2–LiH and TPX™ %U https://doi.org/10.1016/j.mtener.2018.08.008 %X Light metal hydrides are prone to react with oxygen and/or water to produce oxides and/or hydroxides leading to reduction of hydrogen capacities, and deterioration of the hydrogen storage properties. It is therefore critical to address these issues when the materials are to be exposed to air or moisture. In this work, the combination of light metal hydrides, Mg(NH2)2–nLiH with polymethylpentene (TPX™), an air/moisture protective barrier is presented. It was found that the fabricated composites exhibit significant improvement of the metal hydrides stability in air. No oxidation reactions in air can be proven even after air exposure for 90 min. Extending the air-exposure time to 12 h, the reversible hydrogen capacities of these composites are much higher and more stable than they are in the case of the pure metal hydrides. In comparison to the pure metal hydrides, the composites retain the same hydrogen loading capacities and kinetic properties, with respect to the metal hydrides contents. Further, in situ synchrotron radiation powder X-ray radiation diffraction (SR-PXRD) experiments reveal that the thermal decomposition reaction pathways of the 90 min air-exposed composites are the same under air or H2 atmosphere. Moreover, morphology analysis confirms that the metal hydrides remain stable in the polymeric matrix and the three-dimensional integrity is retained, even after performing tens of de/re-hydrogenation cycles. The present study shows a promising way to fabricate air-stable metal hydride-polymer composite hydrogen storage materials that can be handled in ambient conditions. %0 journal article %@ 0020-1669 %A Santoru, A.,Pistidda, C.,Brighi, M.,Chierotti, M.R.,Heere, M.,Karimi, F.,Cao, H.,Capurso, G.,Chaudhary, A.-L.,Gizer, G.,Garroni, S.,Soerby, M.,Hauback, B.C.,Cerny, R.,Klassen, T.,Dornheim, M. %D 2018 %J Inorganic Chemistry %N 6 %P 3197-3205 %R doi:10.1021/acs.inorgchem.7b03232 %T Insights into the Rb–Mg–N–H System: an Ordered Mixed Amide/Imide Phase and a Disordered Amide/Hydride Solid Solution %U https://doi.org/10.1021/acs.inorgchem.7b03232 6 %X The crystal structure of a mixed amide-imide phase, RbMgND2ND, has been solved in the orthorhombic space group Pnma (a = 9.55256(31), b = 3.70772(11) and c = 10.08308(32) Å). A new metal amide-hydride solid solution, Rb(NH2)xH(1–x), has been isolated and characterized in the entire compositional range. The profound analogies, as well as the subtle differences, with the crystal chemistry of KMgND2ND and K(NH2)xH1–x are thoroughly discussed. This approach suggests that the comparable performances obtained using K- and Rb-based additives for the Mg(NH2)2-2LiH and 2LiNH2–MgH2 hydrogen storage systems are likely to depend on the structural similarities of possible reaction products and intermediates. %0 journal article %@ 2075-4701 %A Puszkiel, J.,Castro Riglos, M.V.,Ramallo-Lopez, J.M.,Mizrahi, M.,Gemming, T.,Pistidda, C.,Larochette, P.A.,Bellosta von Colbe, J.,Klassen, T.,Dornheim, M.,Gennari, F. %D 2018 %J Metals %N 11 %P 967 %R doi:10.3390/met8110967 %T New Insight on the Hydrogen Absorption Evolution of the Mg–Fe–H System under Equilibrium Conditions %U https://doi.org/10.3390/met8110967 11 %X Mg2FeH6 is regarded as potential hydrogen and thermochemical storage medium due to its high volumetric hydrogen (150 kg/m3) and energy (0.49 kWh/L) densities. In this work, the mechanism of formation of Mg2FeH6 under equilibrium conditions is thoroughly investigated applying volumetric measurements, X-ray diffraction (XRD), X-ray absorption near edge structure (XANES), and the combination of scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) and high-resolution transmission electron microscopy (HR-TEM). Starting from a 2Mg:Fe stoichiometric powder ratio, thorough characterizations of samples taken at different states upon hydrogenation under equilibrium conditions confirm that the formation mechanism of Mg2FeH6 occurs from elemental Mg and Fe by columnar nucleation of the complex hydride at boundaries of the Fe seeds. The formation of MgH2 is enhanced by the presence of Fe. However, MgH2 does not take part as intermediate for the formation of Mg2FeH6 and acts as solid-solid diffusion barrier which hinders the complete formation of Mg2FeH6. This work provides novel insight about the formation mechanism of Mg2FeH6. %0 journal article %@ 2073-4352 %A Dematteis, E.M.,Vaunois, S.,Pistidda, C.,Dornheim, M.,Baricco, M. %D 2018 %J Crystals %N 2 %P 90 %R doi:10.3390/cryst8020090 %T Reactive Hydride Composite of Mg2NiH4 with Borohydrides Eutectic Mixtures %U https://doi.org/10.3390/cryst8020090 2 %X The development of materials showing hydrogen sorption reactions close to room temperature and ambient pressure will promote the use of hydrogen as energy carrier for mobile and stationary large-scale applications. In the present study, in order to reduce the thermodynamic stability of MgH2, Ni has been added to form Mg2NiH4, which has been mixed with various borohydrides to further tune hydrogen release reactions. De-hydrogenation/re-hydrogenation properties of Mg2NiH4-LiBH4-M(BH4)x (M = Na, K, Mg, Ca) systems have been investigated. Mixtures of borohydrides have been selected to form eutectics, which provide a liquid phase at low temperatures, from 110 °C up to 216 °C. The presence of a liquid borohydride phase decreases the temperature of hydrogen release of Mg2NiH4 but only slight differences have been detected by changing the borohydrides in the eutectic mixture. %0 journal article %@ 0360-3199 %A Hardian, R.,Pistidda, C.,Chaudhary, A.-L.,Capurso, G.,Gizer, G.,Cao, H.,Milanese, C.,Girella, A.,Santoru, A.,Yigit, D.,Dieringa, H.,Kainer, K.U.,Klassen, T.,Dornheim, M. %D 2018 %J International Journal of Hydrogen Energy %N 34 %P 16738-16748 %R doi:10.1016/j.ijhydene.2017.12.014 %T Waste Mg-Al based alloys for hydrogen storage %U https://doi.org/10.1016/j.ijhydene.2017.12.014 34 %X Magnesium has been studied as a potential hydrogen storage material for several decades because of its relatively high hydrogen storage capacity, fast sorption kinetics (when doped with transition metal based additives), and abundance. This research aims to study the possibility to use waste magnesium alloys to produce good quality MgH2. The production costs of hydrogen storage materials is still one of the major barriers disabling scale up for mobile or stationary application. The recycling of magnesium-based waste to produce magnesium hydride will significantly contribute to the cost reduction of this material. This study focuses on the effect of different parameters such as the addition of graphite and/or Nb2O5 as well as the effect of milling time on the material hydrogenation/de-hydrogenation performances. In addition, morphology and microstructural features are also evaluated for all the investigated materials. %0 journal article %@ 1932-7447 %A Le, T.,Pistidda, C.,Puszkiel, J.,Castro Riglos, M.,Karimi, F.,Skibsted, J.,Payandeh GharibDoust, S.,Richter, B.,Emmler, T.,Milanese, C.,Santoru, A.,Hoell, A.,Krumrey, M.,Gericke, E.,Akiba, E.,Jensen, T.,Klassen, T.,Dornheim, M. %D 2018 %J The Journal of Physical Chemistry C %N 14 %P 7642-7655 %R doi:10.1021/acs.jpcc.8b01850 %T Design of a Nanometric AlTi Additive for MgB2-Based Reactive Hydride Composites with Superior Kinetic Properties %U https://doi.org/10.1021/acs.jpcc.8b01850 14 %X Solid-state hydride compounds are a promising option for efficient and safe hydrogen-storage systems. Lithium reactive hydride composite system 2LiBH4 + MgH2/2LiH + MgB2 (Li-RHC) has been widely investigated owing to its high theoretical hydrogen-storage capacity and low calculated reaction enthalpy (11.5 wt % H2 and 45.9 kJ/mol H2). In this paper, a thorough investigation into the effect of the formation of nano-TiAl alloys on the hydrogen-storage properties of Li-RHC is presented. The additive 3TiCl3·AlCl3 is used as the nanoparticle precursor. For the investigated temperatures and hydrogen pressures, the addition of ∼5 wt % 3TiCl3·AlCl3 leads to hydrogenation/dehydrogenation times of only 30 min and a reversible hydrogen-storage capacity of 9.5 wt %. The material containing 3TiCl3·AlCl3 possesses superior hydrogen-storage properties in terms of rates and a stable hydrogen capacity during several hydrogenation/dehydrogenation cycles. These enhancements are attributed to an in situ nanostructure and a hexagonal AlTi3 phase observed by high-resolution transmission electron microscopy. This phase acts in a 2-fold manner, first promoting the nucleation of MgB2 upon dehydrogenation and second suppressing the formation of Li2B12H12 upon hydrogenation/dehydrogenation cycling. %0 journal article %@ 0022-2461 %A Garroni, S.,Delogu, F.,Bonatto, Minella, C.,Pistidda, C.,Cuesta-Lopez, S. %D 2017 %J Journal of Materials Science %N 20 %P 11891-11899 %R doi:10.1007/s10853-017-1220-5 %T Mechanically activated metathesis reaction in NaNH2–MgH2 powder mixtures %U https://doi.org/10.1007/s10853-017-1220-5 20 %X The present work addresses the kinetics of chemical transformations activated by the mechanical processing of powder by ball milling. In particular, attention focuses on the reaction between NaNH2 and MgH2, specific case studies suitably chosen to throw light on the kinetic features emerging in connection with the exchange of anionic ligands induced by mechanical activation. Experimental findings indicate that the mechanical treatment of NaNH2–MgH2 powder mixtures induces a simple metathetic reaction with formation of NaH and Mg(NH2)2 phases. Chemical conversion data obtained by X-ray diffraction analysis have been interpreted using a kinetic model incorporating the statistical character of the mechanical processing by ball milling. The apparent rate constant measuring the reaction rate is related to the volume of powder effectively processed during individual collisions, and tentatively connected with the transfer of mechanical energy across the network formed by the points of contact between the powder particles trapped during collisions. %0 journal article %@ 1614-6832 %A Wang, H.,Wu, G.,Cao, H.,Pistidda, C.,Chaudhary, A.-L.,Garroni, S.,Dornheim, M.,Chen, P. %D 2017 %J Advanced Energy Materials %N 13 %P 1602456 %R doi:10.1002/aenm.201602456 %T Near Ambient Condition Hydrogen Storage in a Synergized Tricomponent Hydride System %U https://doi.org/10.1002/aenm.201602456 13 %X Reversible hydrogen storage over hydrides of light elements (HLEs) under ambient condition has been pursued actively for nearly two decades. However, because of unfavorable thermodynamics and/or severe kinetic barrier of HLEs, limited progress has been made. Here, it is demonstrated that the interaction of LiBH4 with Mg(NH2)2 and LiH, three of the most investigated HLEs, can lead to a fully reversible dehydrogenation/rehydrogenation cycle at temperatures below 373 K. More importantly, with the desorption enthalpy of 24 kJ (mol H2)−1 the dehydrogenation process at 1.0 bar H2 is theoretically possible to be as low as 266 K. Characterization of this combination of HLEs shows that LiBH4 serves as a reagent complexing with intermediates and products of the dehydrogenation of Mg(NH2)2-LiH, and significantly alters the overall thermodynamic and kinetic properties of the system. %0 journal article %@ 0306-0012 %A Paskevecius, M.,Jepsen, L.H.,Schouwink, P.,Cerny, R.,Ravnsbaek, D.B.,Filinchuk, Y.,Dornheim, M.,Besenbacher, F.,Jensen, T.R. %D 2017 %J Chemical Society Reviews %N 5 %P 1565-1634 %R doi:10.1039/c6cs00705h %T Metal borohydrides and derivatives - synthesis, structure and properties %U https://doi.org/10.1039/c6cs00705h 5 %X A wide variety of metal borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing borohydrides related to solid state phosphors and magnetic refrigeration. Two major classes of metal borohydride derivatives have also been discovered: anion-substituted compounds where the complex borohydride anion, BH4−, is replaced by another anion, i.e. a halide or amide ion; and metal borohydrides modified with neutral molecules, such as NH3, NH3BH3, N2H4, etc. Here, we review new synthetic strategies along with structural, physical and chemical properties for metal borohydrides, revealing a number of new trends correlating composition, structure, bonding and thermal properties. These new trends provide general knowledge and may contribute to the design and discovery of new metal borohydrides with tailored properties towards the rational design of novel functional materials. This review also demonstrates that there is still room for discovering new combinations of light elements including boron and hydrogen, leading to complex hydrides with extreme flexibility in composition, structure and properties. %0 journal article %@ 1932-7447 %A Cao, H.,Pistidda, C.,Richter, T.M.M.,Santoru, A.,Milanese, C.,Garroni, S.,Bednarcik, J.,Chaudhary, A.-L.,Gizer, G.,Liermann, H.-P.,Niewa, R.,Ping, C.,Klassen, T.,Dornheim, M. %D 2017 %J The Journal of Physical Chemistry C %N 3 %P 1546-1551 %R doi:10.1021/acs.jpcc.6b12095 %T In Situ X-ray Diffraction Studies on the De/rehydrogenation Processes of the K2[Zn(NH2)4]-8LiH System %U https://doi.org/10.1021/acs.jpcc.6b12095 3 %X In this work, the hydrogen absorption and desorption properties of the system K2[Zn(NH2)4]-8LiH are investigated in detail via in situ synchrotron radiation powder X-ray diffraction (SR-PXD), Fourier transform infrared spectroscopy (FT-IR), and volumetric methods. Upon milling, K2[Zn(NH2)4] and 8LiH react to form 4LiNH2-4LiH-K2ZnH4, and then 4LiNH2-4LiH-K2ZnH4 releases H2 in multiple steps. The final products of the desorption reaction are KH, LiZn13, and Li2NH. During rehydrogenation, KH reacts with LiZn13 under 50 bar of hydrogen producing K3ZnH5. This phase appears to enhance the hydrogenation process which after its formation at ca. 220 °C takes place in only 30 s. The system 4LiNH2-4LiH-K2ZnH4 is shown to be reversible under the applied conditions of vacuum at 400 °C for desorption and 50 bar of H2 at 300 °C for absorption. %0 journal article %@ 1463-9076 %A Puszkiel, J.A.,Castro Riglos, M.V.,Karimi, F.,Santoru, A.,Pistidda, C.,Klassen, T.,Bellosta von Colbe, J.M.,Dornheim, M. %D 2017 %J Physical Chemistry Chemical Physics %N 11 %P 7455-7460 %R doi:10.1039/C6CP08278E %T Changing the dehydrogenation pathway of LiBH4–MgH2 via nanosized lithiated TiO2 %U https://doi.org/10.1039/C6CP08278E 11 %X Nanosized lithiated titanium oxide (LixTiO2) noticeably improves the kinetic behaviour of 2LiBH4 + MgH2. The presence of LixTiO2 reduces the time required for the first dehydrogenation by suppressing the intermediate reaction to Li2B12H12, leading to direct MgB2 formation. %0 journal article %@ 2398-4902 %A Dong, D.,Humphries, T.D.,Sheppard, D.A.,Stansby, B.,Paskevicius, M.,Sofianos, M.V.,Chaudhary, A.-L.,Dornheim, M.,Buckley, C.E. %D 2017 %J Sustainable Energy and Fuels %N 8 %P 1820-1829 %R doi:10.1039/C7SE00316A %T Thermal optimisation of metal hydride reactors for thermal energy storage applications %U https://doi.org/10.1039/C7SE00316A 8 %X Metal hydrides (MHs) are promising candidates as thermal energy storage (TES) materials for concentrated solar thermal applications. A key requirement for this technology is a high temperature heat transfer fluid (HTF) that can deliver heat to the MHs for storage during the day, and remove heat at night time to produce electricity. In this study, supercritical water was used as a HTF to heat a prototype thermochemical heat storage reactor filled with MgH2 powder during H2 sorption, rather than electrical heating of the MH reactor. This is beneficial as the HTF flows through a coil of tubing embedded within the MH bed and is hence in better contact with the MgH2 powder. This internal heating mode produces a more uniform temperature distribution within the reactor by increasing the heat exchange surface area and reducing the characteristic heat exchange distances. Moreover, supercritical water can be implemented as a heat carrier for the entire thermal energy system within a concentrating solar thermal plant, from the receiver, through the heat storage system, and also within a conventional turbine-driven electric power generation system. Thus, the total system energy efficiency can be improved by minimising HTF heat exchangers. %0 journal article %@ 1861-4728 %A Wang, H.,Cao, H.,Pistidda, C.,Garroni, S.,Wu, G.,Klassen, T.,Dornheim, M.,Chen, P. %D 2017 %J Chemistry : An Asian Journal %N 14 %P 1758-1764 %R doi:10.1002/asia.201700287 %T Effects of Stoichiometry on the H2-Storage Properties of Mg(NH2)2–LiH–LiBH4 Tri-Component Systems %U https://doi.org/10.1002/asia.201700287 14 %X The hydrogen desorption pathways and storage properties of 2 Mg(NH2)2–3 LiH–xLiBH4 samples (x=0, 1, 2, and 4) were investigated systematically by a combination of pressure composition isotherm (PCI), differential scanning calorimetric (DSC), and volumetric release methods. Experimental results showed that the desorption peak temperatures of 2 Mg(NH2)2–3 LiH–xLiBH4 samples were approximately 10–15 °C lower than that of 2 Mg(NH2)2–3 LiH. The 2 Mg(NH2)2–3 LiH–4 LiBH4 composite in particular began to release hydrogen at 90 °C, thereby exhibiting superior dehydrogenation performance. All of the LiBH4-doped samples could be fully dehydrogenated and re-hydrogenated at a temperature of 143 °C. The high hydrogen pressure region (above 50 bar) of PCI curves for the LiBH4-doped samples rose as the amount of LiBH4 increased. LiBH4 changed the desorption pathway of the 2 Mg(NH2)2–3 LiH sample under a hydrogen pressure of 50 bar, thereby resulting in the formation of MgNH and molten [LiNH2–2 LiBH4]. That is different from the dehydrogenation pathway of 2 Mg(NH2)2–3 LiH sample without LiBH4, which formed Li2Mg2N3H3 and LiNH2, as reported previously. In addition, the results of DSC analyses showed that the doped samples exhibited two independent endothermic events, which might be related to two different desorption pathways. %0 journal article %@ 0947-6539 %A Cao, H.,Guo, J.,Chang, F.,Pistidda, C.,Zhou, W.,Zhang, X.,Santoru, A.,Wu, H.,Schell, N.,Niewa, R.,Chen, P.,Klassen, T.,Dornheim, M. %D 2017 %J Chemistry - A European Journal %N 41 %P 9766-9771 %R doi:10.1002/chem.201702728 %T Transition and Alkali Metal Complex Ternary Amides for Ammonia Synthesis and Decomposition %U https://doi.org/10.1002/chem.201702728 41 %X A new complex ternary amide, Rb2[Mn(NH2)4], which simultaneously contains both transition and alkali metal catalytic sites, is developed. This is in line with the recently reported TM-LiH composite catalysts, which have been shown to effectively break the scaling relations and achieve ammonia synthesis under mild conditions. Rb2[Mn(NH2)4] can be facilely synthesized by mechanochemical reaction at room temperature. It exhibits two temperature-dependent polymorphs, that is, a low-temperature orthorhombic and a high-temperature monoclinic structure. Rb2[Mn(NH2)4] decomposes to N2, H2, NH3, Mn3N2, and RbNH2 under inert atmosphere; whereas it releases NH3 at a temperature as low as 80 °C under H2 atmosphere. Those unique behaviors enable Rb2[Mn(NH2)4], and its analogue K2[Mn(NH2)4], to be excellent catalytic materials for ammonia decomposition and synthesis. Experimental results show both ammonia decomposition onset temperatures and conversion rates over Rb2[Mn(NH2)4] and K2[Mn(NH2)4] are similar to those of noble metal Ru-based catalysts. More importantly, these ternary amides exhibit superior capabilities in catalyzing NH3 synthesis, which are more than 3 orders of magnitude higher than that of Mn nitride and twice of that of Ru/MgO. The in situ SR-PXD measurement shows that manganese nitride, synergistic with Rb/KH or Rb/K(NH2)xH1−x, are likely the active sites. The chemistry of Rb2/K2[Mn(NH2)x] and Rb/K(NH2)xH1−x with H2/N2 and NH3 correlates closely with the catalytic performance. %0 journal article %@ 1463-9076 %A Cao, H.,Wang, H.,Pistidda, C.,Milanese, C.,Zhang, W.,Chaudhary, A.-L.,Santoru, A.,Garroni, S.,Bednarcik, J.,Liermann, H.-P.,Chen, P.,Klassen, T.,Dornheim, M. %D 2017 %J Physical Chemistry Chemical Physics %N 12 %P 8457-8464 %R doi:10.1039/C7CP00748E %T The effect of Sr(OH)2 on the hydrogen storage properties of the Mg(NH2)2–2LiH system %U https://doi.org/10.1039/C7CP00748E 12 %X The doping effect of Sr(OH)2 on the Mg(NH2)2–2LiH system is investigated considering different amounts of added Sr(OH)2 in the range of 0.05 to 0.2 mol. Experimental results show that both the thermodynamic and the kinetic properties of Mg(NH2)2–2LiH are influenced by the presence of Sr(OH)2. The addition of 0.1 mol Sr(OH)2 leads to a decrease in both the dehydrogenation onset and peak temperatures of ca. 70 and 13 °C, respectively, and an acceleration in the de/re-hydrogenation rates of one time at 150 °C compared to Mg(NH2)2–2LiH alone. Based on differential scanning calorimetry (DSC) analysis, the overall reaction enthalpy of the 0.1 Sr(OH)2-doped sample is calculated to be 44 kJ per mol-H2 and there are two absorption events occurring in the doped sample instead of one in the pristine sample. For the applied experimental conditions, according to the in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Fourier Transform Infrared spectroscopy (FT-IR) analysis, the reaction mechanism has been finally defined: Sr(OH)2, Mg(NH2)2 and LiH react with each other to form SrO, MgO and LiNH2 during ball milling. After heating, SrO interacts with Mg(NH2)2 producing MgO and Sr(NH2)2. Then Mg(NH2)2, LiNH2 and Sr(NH2)2 react with LiH to produce Li2NH, SrNH, Li2Mg(NH)2 and Li2Mg2(NH)3 in traces. After re-hydrogenation, LiSrH3, LiH and LiNH2 are formed along with amorphous Mg(NH2)2. The reasons for the improved kinetics are: (a) during dehydrogenation, the in situ formation of SrNH appears to increase the interfacial contacts between Mg(NH2)2 and LiH and also weakens the N–H bond of Mg(NH2)2; (b) during absorption, the formation of LiSrH3 at around 150 °C could be the key factor for improving the hydrogenation properties. %0 journal article %@ 2050-7488 %A Puszkiel, J.A.,Castro Riglos, M.V.,Ramallo-Lopez, J.M.,Mizrahi, M.,Karimi, F.,Santoru, A.,Hoell, A.,Gennari, F.C.,Arneodo Larochette, P.,Pistidda, C.,Klassen, T.,Bellosta von Colbe J.M.,Dornheim, M. %D 2017 %J Journal of Materials Chemistry A %N 25 %P 12922-12933 %R doi:10.1039/c7ta03117c %T A novel catalytic route for hydrogenation–dehydrogenation of 2LiH + MgB2via in situ formed core–shell LixTiO2 nanoparticles %U https://doi.org/10.1039/c7ta03117c 25 %X Aiming to improve the hydrogen storage properties of 2LiH + MgB2 (Li-RHC), the effect of TiO2 addition to Li-RHC is investigated. The presence of TiO2 leads to the in situ formation of core–shell LixTiO2 nanoparticles during milling and upon heating. These nanoparticles markedly enhance the hydrogen storage properties of Li-RHC. Throughout hydrogenation–dehydrogenation cycling at 400 °C a 1 mol% TiO2 doped Li-RHC material shows sustainable hydrogen capacity of ∼10 wt% and short hydrogenation and dehydrogenation times of just 25 and 50 minutes, respectively. The in situ formed core–shell LixTiO2 nanoparticles confer proper microstructural refinement to the Li-RHC, thus preventing the material's agglomeration upon cycling. An analysis of the kinetic mechanisms shows that the presence of the core–shell LixTiO2 nanoparticles accelerates the one-dimensional interface-controlled mechanism during hydrogenation owing to the high Li+ mobility through the LixTiO2 lattice. Upon dehydrogenation, the in situ formed core–shell LixTiO2 nanoparticles do not modify the dehydrogenation thermodynamic properties of the Li-RHC itself. A new approach by the combination of two kinetic models evidences that the activation energy of both MgH2 decomposition and MgB2 formation is reduced. These improvements are due to a novel catalytic mechanism via Li+ source/sink reversible reactions. %0 journal article %@ 1477-9226 %A Hansen, B.R.S.,Tumanov, N.,Santoru, A.,Pistidda, C.,Bednarcik, J.,Klassen, T.,Dornheim, M.,Filinchuk, Y.,Jensen, T.R. %D 2017 %J Dalton Transactions %N 24 %P 7770-7781 %R doi:10.1039/C7DT01414G %T Synthesis, structures and thermal decomposition of ammine MxB12H12 complexes (M = Li, Na, Ca) %U https://doi.org/10.1039/C7DT01414G 24 %X A series of ammine metal-dodecahydro-closo-dodecaboranes, MxB12H12·nNH3 (M = Li, Na, Ca) were synthesized and their structural and thermal properties studied with in situ time-resolved synchrotron radiation powder X-ray diffraction, thermal analysis, Fourier transformed infrared spectroscopy, and temperature-programmed photographic analysis. The synthesized compounds, Li2B12H12·7NH3, Na2B12H12·4NH3 and CaB12H12·6NH3, contain high amounts of NH3, 43.3, 26.6 and 35.9 wt% NH3, respectively, which can be released and absorbed reversibly at moderate conditions without decomposition, thereby making the closo-boranes favorable ‘host’ materials for ammonia or indirect hydrogen storage in the solid state. In this work, fifteen new ammine metal dodecahydro-closo-dodecaborane compounds are observed by powder X-ray diffraction, of which six are structurally characterized, Li2B12H12·4NH3, Li2B12H12·2NH3, Na2B12H12·4NH3, Na2B12H12·2NH3, CaB12H12·4NH3 and CaB12H12·3NH3. Li2B12H12·4NH3 and Na2B12H12·4NH3 are isostructural and monoclinic (P21/n) whereas Na2B12H12·2NH3 and CaB12H12·3NH3 are both trigonal with space groups Pm1 and Rc, respectively. Generally, coordination between the metal and the icosahedral closo-borane anion is diverse and includes point sharing, edge sharing, or face sharing, while coordination of ammonia always occurs via the lone pair on nitrogen to the metal. Furthermore, a liquid intermediate is observed during heating of Li2B12H12·7NH3. This work provides deeper insight into the structural, physical, and chemical properties related to thermal decomposition and possible ammonia and hydrogen storage. %0 journal article %@ 2304-6740 %A Puszkiel, J.,Garroni, S.,Milanese, C.,Gennari, F.,Klassen, T.,Dornheim, M.,Pistidda, C. %D 2017 %J Inorganics %N 4 %P 74 %R doi:10.3390/inorganics5040074 %T Tetrahydroborates: Development and Potential as Hydrogen Storage Medium %U https://doi.org/10.3390/inorganics5040074 4 %X The use of fossil fuels as an energy supply becomes increasingly problematic from the point of view of both environmental emissions and energy sustainability. As an alternative, hydrogen is widely regarded as a key element for a potential energy solution. However, different from fossil fuels such as oil, gas, and coal, the production of hydrogen requires energy. Alternative and intermittent renewable sources such as solar power, wind power, etc., present multiple advantages for the production of hydrogen. On one hand, the renewable sources contribute to a remarkable reduction of pollutants released to the air. On the other hand, they significantly enhance the sustainability of energy supply. In addition, the storage of energy in form of hydrogen has a huge potential to balance an effective and synergetic utilization of the renewable energy sources. In this regard, hydrogen storage technology presents a key roadblock towards the practical application of hydrogen as “energy carrier”. Among the methods available to store hydrogen, solid-state storage is the most attractive alternative both from the safety and the volumetric energy density points of view. Because of their appealing hydrogen content, complex hydrides and complex hydride-based systems have attracted considerable attention as potential energy vectors for mobile and stationary applications. In this review, the progresses made over the last century on the development in the synthesis and research on the decomposition reactions of homoleptic tetrahydroborates is summarized. Furthermore, theoretical and experimental investigations on the thermodynamic and kinetic tuning of tetrahydroborates for hydrogen storage purposes are herein reviewed. %0 journal article %@ 0360-3199 %A Chaudhary, A.-L.,Dietzel, S.,Li, H.-W.,Akiba, E.,Bergemann, N.,Pistidda, C.,Klassen, T.,Dornheim, M. %D 2017 %J International Journal of Hydrogen Energy %N 16 %P 11422-11428 %R doi:10.1016/j.ijhydene.2017.02.033 %T Synthesis of Mg2FeD6 under low pressure conditions for Mg2FeH6 hydrogen storage studies %U https://doi.org/10.1016/j.ijhydene.2017.02.033 16 %X Mg2FeD6 is successfully synthesised with various degrees of purity using reactive ball milling and annealing under low pressure deuterium conditions to a maximum of 10 bar. The deuteride of the low cost ternary metal hydride Mg2FeH6, is synthesised to enable further characterisation studies such as isotopic exchange behaviour. Both on laboratory and industrial scales, keeping the pressure low reduces the need for expensive compression systems and also minimises the quantity of gas necessary for use; therefore it is important to assess synthesis under these cost effective conditions. This is especially the case when using a specialised gas such as high purity deuterium. The maximum pressure chosen is 10 bar, to comply with the High Pressure Safety Act in Japan. This Safety Act limits the use of any gas including hydrogen and deuterium to 10 bar eliminating the use of traditional synthesis methods for Mg2FeH6 or Mg2FeD6 synthesis at high pressure (120 bar). Ball milling parameters such as milling times, ball to powder ratios as well as sintering times were altered to achieve improved Mg2FeD6 yields under these low pressure conditions. %0 journal article %@ 2304-6740 %A Li, G.,Matsuo, M.,Takagi, S.,Chaudhary, A.-L.,Sato, T.,Dornheim, M.,Orimo, S.-I. %D 2017 %J Inorganics %N 4 %P 81 %R doi:10.3390/inorganics5040081 %T Thermodynamic Properties and Reversible Hydrogenation of LiBH4–Mg2FeH6 Composite Materials %U https://doi.org/10.3390/inorganics5040081 4 %X In previous studies, complex hydrides LiBH4 and Mg2FeH6 have been reported to undergo simultaneous dehydrogenation when ball-milled as composite materials (1 − x)LiBH4 + xMg2FeH6. The simultaneous hydrogen release led to a decrease of the dehydrogenation temperature by as much as 150 K when compared to that of LiBH4. It also led to the modified dehydrogenation properties of Mg2FeH6. The simultaneous dehydrogenation behavior between stoichiometric ratios of LiBH4 and Mg2FeH6 is not yet understood. Therefore, in the present work, we used the molar ratio x = 0.25, 0.5, and 0.75, and studied the isothermal dehydrogenation processes via pressure–composition–isothermal (PCT) measurements. The results indicated that the same stoichiometric reaction occurred in all of these composite materials, and x = 0.5 was the molar ratio between LiBH4 and Mg2FeH6 in the reaction. Due to the optimal composition ratio, the composite material exhibited enhanced rehydrogenation and reversibility properties: the temperature and pressure of 673 K and 20 MPa of H2, respectively, for the full rehydrogenation of x = 0.5 composite, were much lower than those required for the partial rehydrogenation of LiBH4. Moreover, the x = 0.5 composite could be reversibly hydrogenated for more than four cycles without degradation of its H2 capacity. %0 journal article %@ 1932-7447 %A Carillo-Bucio, J.L.,Saldan, I.,Pistidda, C.,Karimi, F.,Suarez-Alcantara, K.,Dornheim, M.,Klassen, T. %D 2017 %J The Journal of Physical Chemistry C %N 8 %P 4093-4102 %R doi:10.1021/acs.jpcc.6b09776 %T Hydrogenation Study of NaF/NaH/MgB2 Reactive Hydride Composites %U https://doi.org/10.1021/acs.jpcc.6b09776 8 %X The hydrogenation of NaF/9NaH + 5MgB2 and NaF/2NaH + 1.5MgB2 reactive hydride composites (RHC) was studied by volumetric titration (kinetics and PCI curves), in situ synchrotron radiation powder X-ray diffraction (SR-PXD), high-pressure differential scanning calorimetry (HP-DSC), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM). A hydrogen uptake between 4.1 and 4.8 wt % was observed when the H2 pressure was in the range between 25 and 50 bar, and the temperature was kept constant at 325 °C. PCI curves indicate a hydrogenation equilibrium pressure of 2 and 8 bar at 325 °C for NaF/9NaH + 5MgB2 and NaF/2NaH + 1.5MgB2, respectively. Synchrotron radiation powder X-ray diffraction revealed the formation of solid solutions of NaF–NaH after milling and a change in the reaction pathway compared to a reported nondoped 2NaH + MgB2 reactive hydride composite. Formation of the stable side-product NaMgH2F was found as a drawback for hydrogen storage capacity and reversibility. FT-IR indicates no hydrogen to fluorine substitution in the NaBH4 product. %0 journal article %@ 1359-7345 %A Bergemann, N.,Pistidda, C.,Milanese, C.,Emmler, T.,Karimi, F.,Chaudhary, A.-L.,Chierotti, M.R.,Klassen, T.,Dornheim, M. %D 2016 %J Chemical Communications : ChemComm %N 26 %P 4836-4839 %R doi:10.1039/c5cc09991a %T Ca(BH4)2–Mg2NiH4: on the pathway to a Ca(BH4)2 system with a reversible hydrogen cycle %U https://doi.org/10.1039/c5cc09991a 26 %X The Ca(BH4)2–Mg2NiH4 system presented here is, to the best of our knowledge, the first described Ca(BH4)2-based hydride composite that reversibly transfers boron from the Ca-based compound(s) to the reaction partner. The ternary boride MgNi2.5B2 is formed upon dehydrogenation and the formation of Ca(BH4)2 upon rehydrogenation is confirmed. %0 journal article %@ 1359-7345 %A Santoru, A.,Pistidda, C.,Soerby, M.H.,Chierotti, M.R.,Garroni, S.,Pinatel, E.,Karimi, F.,Cao, H.,Bergemann, N.,Le, T.T.,Puszkiel, J.,Gobetto, R.,Baricco, M.,Hauback, B.C.,Klassen, T.,Dornheim, M. %D 2016 %J Chemical Communications : ChemComm %N 79 %P 11760-11763 %R doi:10.1039/c6cc05777b %T KNH2–KH: a metal amide–hydride solid solution %U https://doi.org/10.1039/c6cc05777b 79 %X We report for the first time the formation of a metal amide–hydride solid solution. The dissolution of KH into KNH2 leads to an anionic substitution, which decreases the interaction among NH2− ions. The rotational properties of the high temperature polymorphs of KNH2 are thereby retained down to room temperature. %0 journal article %@ 1463-9076 %A Santoru, A.,Garroni, S.,Pistidda, C.,Milanese, C.,Girella, A.,Marini, A.,Masolo, E.,Valentoni, A.,Bergemann, N.,Le, T.T.,Cao, H.,Haase, D.,Balmes, O.,Taube, K.,Mulas, G.,Enzo, S.,Klassen, T.,Dornheim, M. %D 2016 %J Physical Chemistry Chemical Physics %N 5 %P 3910-3920 %R doi:10.1039/C5CP06963G %T A new potassium-based intermediate and its role in the desorption properties of the K–Mg–N–H system %U https://doi.org/10.1039/C5CP06963G 5 %X New insights into the reaction pathways of different potassium/magnesium amide–hydride based systems are discussed. In situ SR-PXD experiments were for the first time performed in order to reveal the evolution of the phases connected with the hydrogen releasing processes. Evidence of a new K–N–H intermediate is shown and discussed with particular focus on structural modification. Based on these results, a new reaction mechanism of amide–hydride anionic exchange is proposed. %0 journal article %@ 0378-7753 %A Boerries, S.,Metz, O.,Pranzas, P.K.,Bellosta von Colbe, J.M.,Buecherl, T.,Dornheim, M.,Schreyer, A. %D 2016 %J Journal of Power Sources %N %P 567-577 %R doi:10.1016/j.jpowsour.2016.08.040 %T Optimization and comprehensive characterization of metal hydride based hydrogen storage systems using in-situ Neutron Radiography %U https://doi.org/10.1016/j.jpowsour.2016.08.040 %X For the storage of hydrogen, complex metal hydrides are considered as highly promising with respect to capacity, reversibility and safety. The optimization of corresponding storage tanks demands a precise and time-resolved investigation of the hydrogen distribution in scaled-up metal hydride beds. In this study it is shown that in situ fission Neutron Radiography provides unique insights into the spatial distribution of hydrogen even for scaled-up compacts and therewith enables a direct study of hydrogen storage tanks. A technique is introduced for the precise quantification of both time-resolved data and a priori material distribution, allowing inter alia for an optimization of compacts manufacturing process. For the first time, several macroscopic fields are combined which elucidates the great potential of Neutron Imaging for investigations of metal hydrides by going further than solely ’imaging’ the system: A combination of in-situ Neutron Radiography, IR-Thermography and thermodynamic quantities can reveal the interdependency of different driving forces for a scaled-up sodium alanate pellet by means of a multi-correlation analysis. A decisive and time-resolved, complex influence of material packing density is derived. The results of this study enable a variety of new investigation possibilities that provide essential information on the optimization of future hydrogen storage tanks. %0 journal article %@ 0254-0584 %A Utke, R.,Thiangviriya, S.,Javadian, P.,jensen, T.R.,Milanese, C.,Klassen, T.,Dornheim, M. %D 2016 %J Materials Chemistry and Physics %N %P 136-141 %R doi:10.1016/j.matchemphys.2015.11.040 %T 2LiBH4–MgH2 nanoconfined into carbon aerogel scaffold impregnated with ZrCl4 for reversible hydrogen storage %U https://doi.org/10.1016/j.matchemphys.2015.11.040 %X Nanoconfinement of 2LiBH4–MgH2 composite into carbon aerogel scaffold (CAS) impregnated with zirconium (IV) chloride (ZrCl4) for reversible hydrogen storage is proposed. Nanoconfined samples prepared with hydride:ZrCl4-doped CAS weight ratios of 1:1, 1:2, and 1:3 are prepared by melt infiltration technique. Successful nanoconfinement of all samples is confirmed and it is found that the sample with high content of hydride with respect to ZrCl4-doped CAS (1:1 weight ratio) shows partial pore blocking. The most suitable hydride:ZrCl4-doped CAS weight ratio providing the best performance based on dehydrogenation temperature and kinetics as well as hydrogen storage capacity is 1:2. Reduction of dehydrogenation temperature and faster kinetics are obtained after doping with ZrCl4. Up to 97 and 93% of theoretical hydrogen storage capacity are released and reproduced after four cycles of nanoconfined sample with ZrCl4 (1:2 weight ratio). Deficient hydrogen content with respect to theoretical capacity can be due to partial dehydrogenation during melt infiltration and formation of thermally stable [B12H12]2- phases during cycling. %0 journal article %@ 0947-8396 %A Callini, E.,Atakli, Z.Oe.K.,Hauback, B.C.,Orimo, S.-I.,Jensen, C.,Dornheim, M.,Grant, D.,Cho, Y.W.,Chen, P.,Hjoervarsson, B.,de Jongh, P.,Weidenthaler, C.,Baricco, M.,Paskevicius, M.,Jensen, T.R.,bowden, M.E.,Autrey, T.S.,Zuettel, A. %D 2016 %J Applied Physics A %N 4 %P 353 %R doi:10.1007/s00339-016-9881-5 %T Complex and liquid hydrides for energy storage %U https://doi.org/10.1007/s00339-016-9881-5 4 %X The research on complex hydrides for hydrogen storage was initiated by the discovery of Ti as a hydrogen sorption catalyst in NaAlH4 by Boris Bogdanovic in 1996. A large number of new complex hydride materials in various forms and combinations have been synthesized and characterized, and the knowledge regarding the properties of complex hydrides and the synthesis methods has grown enormously since then. A significant portion of the research groups active in the field of complex hydrides is collaborators in the International Energy Agreement Task 32. This paper reports about the important issues in the field of complex hydride research, i.e. the synthesis of borohydrides, the thermodynamics of complex hydrides, the effects of size and confinement, the hydrogen sorption mechanism and the complex hydride composites as well as the properties of liquid complex hydrides. This paper is the result of the collaboration of several groups and is an excellent summary of the recent achievements. %0 journal article %@ 0360-3199 %A Paskevicius, M.,Filsoe, U.,Karimi, F.,Puszkiel, J.,Pranzas, P.K.,Pistidda, C.,Hoell, A.,Welter, E.,Schreyer, A.,Klassen, T.,Dornheim, M.,Jensen, T.R. %D 2016 %J International Journal of Hydrogen Energy %N 7 %P 4159-4167 %R doi:10.1016/j.ijhydene.2015.12.185 %T Cyclic stability and structure of nanoconfined Ti-doped NaAlH4 %U https://doi.org/10.1016/j.ijhydene.2015.12.185 7 %X NaAlH4 was melt infiltrated within a CO2 activated carbon aerogel, which had been preloaded with TiCl3. Nanoconfinement was verified by Small Angle X-Ray Scattering (SAXS) and the nature of the Ti was investigated with Anomalous SAXS (ASAXS) and X-Ray Absorption Near Edge Structure (XANES) to determine its size and chemical state. The Ti is found to be in a similar state to that found in the bulk Ti-doped NaAlH4 system where it exists as Al1−xTix nanoalloys. Crystalline phases exist within the carbon aerogel pores, which are analysed by in-situ Powder X-Ray Diffraction (PXD) during hydrogen cycling. The in-situ data reveals that the hydrogen release from NaAlH4 and its hydrogen uptake occurs through the Na3AlH6 intermediate when confined at this size scale. The hydrogen capacity from the nanoconfined NaAlH4 is found to initially be much higher in this CO2 activated aerogel compared with previous studies into unactivated aerogels. %0 journal article %@ 0947-8396 %A Crivello, J.-C.,Denys, R.V.,Dornheim, M.,Felderhoff, M.,Grant, D.M.,Huot, J.,Jensen, T.R.,de Jongh, P.,Latroche, M.,Walker, G.S.,Webb, C.J.,Yartys, V.A. %D 2016 %J Applied Physics A %N %P 85 %R doi:10.1007/s00339-016-9601-1 %T Mg-based compounds for hydrogen and energy storage %U https://doi.org/10.1007/s00339-016-9601-1 %X Magnesium-based alloys attract significant interest as cost-efficient hydrogen storage materials allowing the combination of high gravimetric storage capacity of hydrogen with fast rates of hydrogen uptake and release and pronounced destabilization of the metal–hydrogen bonding in comparison with binary Mg–H systems. In this review, various groups of magnesium compounds are considered, including (1) RE–Mg–Ni hydrides (RE = La, Pr, Nd); (2) Mg alloys with p-elements (X = Si, Ge, Sn, and Al); and (3) magnesium alloys with d-elements (Ti, Fe, Co, Ni, Cu, Zn, Pd). The hydrogenation–disproportionation–desorption–recombination process in the Mg-based alloys (LaMg12, LaMg11Ni) and unusually high-pressure hydrides synthesized at pressures exceeding 100 MPa (MgNi2H3) and stabilized by Ni–H bonding are also discussed. The paper reviews interrelations between the properties of the Mg-based hydrides and p–T conditions of the metal–hydrogen interactions, chemical composition of the initial alloys, their crystal structures, and microstructural state. %0 journal article %@ 0360-3199 %A Heere, M.,Soerby, M.H.,Pistidda, C.,Dornheim, M.,Hauback, B.C. %D 2016 %J International Journal of Hydrogen Energy %N 30 %P 13101-13108 %R doi:10.1016/j.ijhydene.2016.05.153 %T Milling time effect of Reactive Hydride Composites of NaF-NaH-MgB2 investigated by in situ powder diffraction %U https://doi.org/10.1016/j.ijhydene.2016.05.153 30 %X Light metal complex borohydrides have high hydrogen storage capacities but suffer from drawbacks of slow hydrogen sorption kinetics, poor reversibility and high thermodynamic stability. The NaF + 9NaH + 5MgB2 composite has a theoretical hydrogen capacity of 7.7 wt% H assuming the formation of 10NaBH3.9F0.1 + 5MgH2. Hydrogenation and dehydrogenation properties as well as the effect of different ball milling times have been investigated. The in situ hydrogenation is faster in the composite ball milled for 87 h than the 5 h milled composite. A boron-rich phase with space group Pa-3, a = 7.4124(5) Å was formed during hydrogenation at 325 °C and 50 bar hydrogen for both short and long milling times. In the long milled composite the boron-rich phase disappeared after 3 h of hydrogenation, whereas it became a major phase in the short milled composite after 1.5 h of hydrogenation. NaBH4 was formed at 206 °C. NaMgH1-xFx was formed at 290 °C instead of the assumed MgH2. The same phases formed at 268 °C and 325 °C, respectively, and only in minor amounts in the short milled composite. Ex situ hydrogenation in a Sieverts' type apparatus at the same temperature and hydrogen pressure conditions followed a different reaction pathway with formation of MgH2 in addition to NaBH4 and NaMgH3-xFx (0 ≤ x ≤ 1). The measured hydrogen uptake was 6.0 and 6.3 wt% for the long and short milled composites, respectively. %0 journal article %@ 0947-8396 %A Crivello, J.-C.,Dam, B.,Denys, R.V.,Dornheim, M.,Grant, D.M.,Huot, J.,jensen, T.R.,de jongh, P.,Latroche, M.,Milanese, C.,Milcius, D.,Walker, G.S.,Webb, C.J.,Zlotea, C.,Yartys, V.A. %D 2016 %J Applied Physics A %N 2 %P 97 %R doi:10.1007/s00339-016-9602-0 %T Review of magnesium hydride-based materials: development and optimisation %U https://doi.org/10.1007/s00339-016-9602-0 2 %X Magnesium hydride has been studied extensively for applications as a hydrogen storage material owing to the favourable cost and high gravimetric and volumetric hydrogen densities. However, its high enthalpy of decomposition necessitates high working temperatures for hydrogen desorption while the slow rates for some processes such as hydrogen diffusion through the bulk create challenges for large-scale implementation. The present paper reviews fundamentals of the Mg–H system and looks at the recent advances in the optimisation of magnesium hydride as a hydrogen storage material through the use of catalytic additives, incorporation of defects and an understanding of the rate-limiting processes during absorption and desorption. %0 journal article %@ 0947-8396 %A Capurso, G.,Schiavo, B.,Jepsen, J.,Lozano, G.,Metz, O.,Saccone, A.,de negri, S.,Bellosta von Colbe, J.M.,Klassen, T.,Dornheim, M. %D 2016 %J Applied Physics A %N 3 %P 236 %R doi:10.1007/s00339-016-9771-x %T Development of a modular room-temperature hydride storage system for vehicular applications %U https://doi.org/10.1007/s00339-016-9771-x 3 %X The subject of this paper concerns the development of a vehicular hydrogen tank system, using a commercial interstitial metal hydride as storage material. The design of the tank was intended to feed a fuel cell in a light prototype vehicle, and the chosen hydride material, Hydralloy C5 by GfE, was expected to be able to absorb and desorb hydrogen in a range of pressure suitable for this purpose. A systematic analysis of the material in laboratory scale allows an extrapolation of the thermodynamic and reaction kinetics data. The following development of the modular tank was done according to the requirements of the prototype vehicle propulsion system and led to promising intermediate results. The modular approach granted flexibility in the design, allowing both to reach carefully the design goals and to learn the limiting factors in the sorption process. Proper heat management and suitable equipment remain key factors in order to achieve the best performances. %0 journal article %@ 0360-3199 %A Callini, E.,Aguey-Zinsou, K.-F.,Ahuja, R.,Ares, J.R.,Bals, S.,Biliskov, N.,Chakraborty, S.,Charalambopoulou, G.,Chaudhary, A,-L.,Cuevas, F.,Dam, B.,de Jongh, P.,Dornheim, M.,Filinchuk, Y.,Grbovic Novakovic, J.,Hirscher, M.,Jensen, T.R.,Jensen, P.B.,Novakovic, N.,Lai, Q.,Leardini, F.,Gattia, D.M.,Pasquini, L.,Steriotis, T.,Turner, S.,Vegge, T.,Zuettel, A.,Montone, A. %D 2016 %J International Journal of Hydrogen Energy %N 32 %P 14404-14428 %R doi:10.1016/j.ijhydene.2016.04.025 %T Nanostructured materials for solid-state hydrogen storage: A review of the achievement of COST Action MP1103 %U https://doi.org/10.1016/j.ijhydene.2016.04.025 32 %X In the framework of the European Cooperation in Science and Technology (COST) Action MP1103 Nanostructured Materials for Solid-State Hydrogen Storage were synthesized, characterized and modeled. This Action dealt with the state of the art of energy storage and set up a competitive and coordinated network capable to define new and unexplored ways for Solid State Hydrogen Storage by innovative and interdisciplinary research within the European Research Area. An important number of new compounds have been synthesized: metal hydrides, complex hydrides, metal halide ammines and amidoboranes. Tuning the structure from bulk to thin film, nanoparticles and nanoconfined composites improved the hydrogen sorption properties and opened the perspective to new technological applications. Direct imaging of the hydrogenation reactions and in situ measurements under operando conditions have been carried out in these studies. Computational screening methods allowed the prediction of suitable compounds for hydrogen storage and the modeling of the hydrogen sorption reactions on mono-, bi-, and three-dimensional systems. This manuscript presents a review of the main achievements of this Action. %0 journal article %@ 1359-7345 %A Cao, H.,Santoru, A.,Pistidda, C.,Richter, T.M.M.,Chaudhary, A.-L.,Gizer, G.,Niewa, R.,Chen, P.,Klassen, T.,Dornheim, M. %D 2016 %J Chemical Communications : ChemComm %N 29 %P 5100-5103 %R doi:10.1039/C6CC00719H %T New synthesis route for ternary transition metal amides as well as ultrafast amide–hydride hydrogen storage materials %U https://doi.org/10.1039/C6CC00719H 29 %X K2[Mn(NH2)4] and K2[Zn(NH2)4] were successfully synthesized via a mechanochemical method. The mixture of K2[Mn(NH2)4] and LiH showed excellent rehydrogenation properties. In fact, after dehydrogenation K2[Mn(NH2)4]-8LiH fully rehydrogenates within 60 seconds at ca. 230 °C and 5 MPa of H2. This is one of the fastest rehydrogenation rates in amide–hydride systems known to date. This work also shows a strategy for the synthesis of transition metal nitrides by decomposition of the mixtures of M[M′(NH2)n] (where M is an alkali or alkaline earth metal and M′ is a transition metal) and metal hydrides. %0 journal article %@ 0947-8396 %A Sheppard, D.A.,Paskevicius, M.,Humphries, T.D.,Felderhoff, M.,Capurso, G.,Bellosta von Colbe, J.,Dornheim, M.,Klassem, T.,Ward, P.A.,Teprovich, J.A.Jr.,Corgnale, C.,Zidan, R.,Grant, D.M.,Buckley, C.E. %D 2016 %J Applied Physics A %N 4 %P 395 %R doi:10.1007/s00339-016-9825-0 %T Metal hydrides for concentrating solar thermal power energy storage %U https://doi.org/10.1007/s00339-016-9825-0 4 %X The development of alternative methods for thermal energy storage is important for improving the efficiency and decreasing the cost of concentrating solar thermal power. We focus on the underlying technology that allows metal hydrides to function as thermal energy storage (TES) systems and highlight the current state-of-the-art materials that can operate at temperatures as low as room temperature and as high as 1100 °C. The potential of metal hydrides for thermal storage is explored, while current knowledge gaps about hydride properties, such as hydride thermodynamics, intrinsic kinetics and cyclic stability, are identified. The engineering challenges associated with utilising metal hydrides for high-temperature TES are also addressed. %0 journal article %@ 0360-3199 %A Pireddu, G.,Valentoni, A.,Bonatto Minella, C.,Pistidda, C.,Milanese, C.,Enzo, S.,Mulas, G.,Garroni, S. %D 2015 %J International Journal of Hydrogen Energy %N 4 %P 1829-1835 %R doi:10.1016/j.ijhydene.2014.11.145 %T Comparison of the thermochemical and mechanochemical transformations in the 2NaNH2–MgH2 system %U https://doi.org/10.1016/j.ijhydene.2014.11.145 4 %X We focus on the chemical transformations involved in the 2NaNH2 + MgH2 system subjected to thermal and mechanical inputs. Transformations occurring on the powder mixture during thermochemical and mechanochemical processes are described by ex-situ X-ray powder diffraction (XRPD), FT-IR spectroscopy, differential scanning calorimetry and manometric measurements. In the thermally activated samples, the reaction take place through the fast formation of Mg(NH2)2 and NaH via metathesis reaction between NaNH2 and MgH2 at 125 °C. FT-IR analysis confirms the presence of unreacted NaNH2 and a new Na-amide phase that could be ascribable to tetramide, Na2Mg(NH2)4. At higher temperature, the formation of new imide-amide phase is detected, stables up to 300 °C. On the other hand when the initial mixture is subjected to mechanochemical processing for longer milling time (50 h), only Mg(NH2)2 and NaH are produced. The hydrogen desorption reaction of the as-milled Mg(NH2)2–NaH mixture starts at 100 °C together with the formation of the NaMg(NH2)(NH) imide-amide phase, equally to the initial mixture. %0 journal article %@ 0021-8898 %A Hansen, B.R.S.,Moeller, K.T.,Paskevicius, M.,Dippel, A.-C.,Walter, P.,Webb, C.J.,Pistidda, C.,Bergemann, N.,Dornheim, M.,Klassen, T.,Joergensen, J.-E.,Jensen, T.R. %D 2015 %J Journal of Applied Crystallography %N 4 %P 1234-1241 %R doi:10.1107/S1600576715011735 %T In situ X-ray diffraction environments for high-pressure reactions %U https://doi.org/10.1107/S1600576715011735 4 %X New sample environments and techniques specifically designed for in situ powder X-ray diffraction studies up to 1000 bar (1 bar = 105 Pa) gas pressure are reported and discussed. The cells can be utilized for multiple purposes in a range of research fields. Specifically, investigations of gas-solid reactions and sample handling under inert conditions are undertaken here. Sample containers allowing the introduction of gas from one or both ends are considered, enabling the possibility of flow-through studies. Various containment materials are evaluated, e.g. capillaries of single-crystal sapphire (Al2O3), quartz glass (SiO2), stainless steel (S316) and glassy carbon (Sigradur K), and burst pressures are calculated and tested for the different tube materials. In these studies, high hydrogen pressure is generated with a metal hydride hydrogen compressor mounted in a closed system, which allows reuse of the hydrogen gas. The advantages and design considerations of the in situ cells are discussed and their usage is illustrated by a case study. %0 journal article %@ 0360-3199 %A Plerdsranoy, P.,Wiset, N.,Milanese, C.,Laipple, D.,Marini, A.,Klassen, T.,Dornheim, M.,Gosalawit-Utke, R. %D 2015 %J International Journal of Hydrogen Energy %N 1 %P 392-402 %R doi:10.1016/j.ijhydene.2014.10.090 %T Improvement of thermal stability and reduction of LiBH4/polymer host interaction of nanoconfined LiBH4 for reversible hydrogen storage %U https://doi.org/10.1016/j.ijhydene.2014.10.090 1 %X Addition of multi-wall carbon nanotube (MWCNT) and NaAlH4 into nanoconfined LiBH4–PcB (poly (methyl methacrylate)–co–butyl methacrylate) for improving thermal stability and reducing LiBH4/PcB interaction is proposed. The greater the amount of gases desorbed due to polymer (PcB) degradation, the less the thermal stability of polymer host. During dehydrogenation of nanoconfined LiBH4–PcB, combination of gases due to PcB degradation is 64.3% with respect to H2 content, while those of nanoconfined samples doped with MWCNT and NaAlH4 are only 9 and 7.9%, respectively. The LiBH4/PcB (i.e., B⋯OCH3) interaction is quantitatively evaluated by FTIR technique. The more the ratio of peak area between υ(B–H) (from LiBH4) and υ(CO) (from PcB), the lower the LiBH4/PcB interaction. It is found that by adding small amount of MWCNT and NaAlH4, this ratio significantly increases up to 78%. This is in agreement with B 1s XPS results, where the relative amount of BxOy (x/y = 3) to LiBH4 decreases after adding MWCNT and NaAlH4 into nanoconfined LiBH4–PcB. It should be remarked that significant improvement of thermal stability and decrease of LiBH4/PcB interaction after adding MWCNT and NaAlH4 into nanoconfined LiBH4–PcB result in considerable amount of hydrogen release and uptake as well as hydrogen reproducibility during cycling. However, the dispersion of MWCNT is still one of the most critical factors to be concerned due to probably its hindrance for hydrogen diffusion. %0 journal article %@ 1932-7447 %A Suarez-Alcantara, K.,Boesenberg, U.,Saldan, I.,Klassen, T.,Dornheim, M. %D 2015 %J The Journal of Physical Chemistry C %N 40 %P 22826-22831 %R doi:10.1021/acs.jpcc.5b07444 %T On the Hydrogenation of a NaH/AlB2 Mixture %U https://doi.org/10.1021/acs.jpcc.5b07444 40 %X A mixture of 3NaH/AlB2 was prepared by ball-milling; its hydriding reaction was studied between 375–425 °C and 25–50 bar hydrogen pressure by means of volumetric titration. The hydriding reaction was characterized by means of in situ synchrotron radiation powder X-ray diffraction and high-pressure differential scanning calorimetry. Hydriding reaction took place at the molten state, and its reaction products were NaBH4 and Al. The scanning electron microscopy images of the material revealed that the material morphology changes after hydriding. A maximum hydrogen uptake of 4.7 wt % was registered for the hydriding experiment at 425 °C and 50 bar hydrogen pressure. Dehydriding reaction was studied by means of volumetric titration and differential scanning calorimetry. The dehydriding reaction at 425 °C and 1 bar argon pressure registered a release of 2.4 wt %. The low dehydriding level was attributed to the reduction of the available particle surface upon melting of the material during the hydriding reaction. %0 journal article %@ 1359-6454 %A Chaudhary, A.-L.,Sheppard, D.A.,Paskevicius, M.,Pistidda, C.,Dornheim, M.,Buckley, C.E. %D 2015 %J Acta Materialia %N %P 244-253 %R doi:10.1016/j.actamat.2015.05.046 %T Reaction kinetic behaviour with relation to crystallite/grain size dependency in the Mg–Si–H system %U https://doi.org/10.1016/j.actamat.2015.05.046 %X An empirical understanding of the relationship between crystallite size and reaction kinetics for the dehydrogenation of MgH2 in the presence of Si was determined. MgH2 was combined with Si under different conditions to obtain varying crystallite sizes of both reactants. Thermal analysis and isothermal desorption were undertaken to obtain reaction kinetic information and therefore determine activation energies as well as the rate limiting step for each of the different crystallite sizes. It was found that there is a strong correlation between crystallite size and activation energy for the growth of the Mg2Si phase, however, any correlation between the nucleation (of Mg2Si) activation energy was less evident. Direct measurements of kinetic behaviour from a manometric Sieverts apparatus showed that initial reaction kinetics were fastest when MgH2 was mixed with Si nanoparticles, however, this sample was not able to fully desorb. Data from the Sieverts measurements were then used with well-known theoretical models to determine the rate limiting step of the reaction. The three dimensional Carter–Valensi (or contracting volume) diffusion model could be used to describe the rate limiting step for most of the reactions. These results have led to a proposed mechanism for the formation of Mg2Si during the decomposition reaction. %0 journal article %@ 1932-7447 %A Suarez-Alcantara, K.,Soerby, M.H.,Pistidda, C.,Karimi, F.,Saldan, I.,Hauback, B.C.,Klassen, T.,Dornheim, M. %D 2015 %J The Journal of Physical Chemistry C %N 21 %P 11430-11437 %R doi:10.1021/acs.jpcc.5b01961 %T Synchrotron Diffraction Studies of Hydrogen Absorption/Desorption on CaH2 + MgB2 Reactive Hydride Composite Mixed With Fluorinated Compounds %U https://doi.org/10.1021/acs.jpcc.5b01961 21 %X The reactive hydride composites 9CaH2 + CaF2 + 10MgB2, 10Ca(BH4)2 + 9MgH2 + MgF2, and 9Ca(BH4)2 + Ca(BF4)2 + 10MgH2 were prepared by ball milling. Their properties toward hydrogen absorption/desorption were tested by means of manometric measurements. The highest hydrogen storage capacity was obtained for 9CaH2 + CaF2 + 10MgB2 (7.6 wt %) at the first cycle. The effects of CaF2, MgF2, or Ca(BF4)2 on the dehydrogenation reaction were studied by means of in situ synchrotron radiation powder X-ray diffraction (in situ SR-PXD) and differential scanning calorimetry (DSC). The high resolution SR-PXD technique was used to confirm the formation of hydrogenated products and side products in the 9CaH2 + CaF2 + 10MgB2 reactive hydride composites. These studies indicate the formation of a complex mixture of phases. %0 journal article %@ 0925-8388 %A Bonatto Minella, C.,Garroni, S.,Pistidda, C.,Baro, M.D.,Gutfleisch, O.,Klassen, T.,Dornheim, M. %D 2015 %J Journal of Alloys and Compounds %N %P 989-994 %R doi:10.1016/j.jallcom.2014.11.038 %T Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH4)2–MgH2 system %U https://doi.org/10.1016/j.jallcom.2014.11.038 %X In the last decade, alkaline and alkaline earth metal tetrahydroborates have been the focuses of the research due to their high gravimetric and volumetric hydrogen densities. Among them, Ca(BH4)2 and the Ca(BH4)2 + MgH2 reactive hydride composites (RHC), were calculated to have the ideal thermodynamic properties which fall within the optimal range for mobile applications.,In this study, the addition of NbF5 or TiF4 to the Ca(BH4)2 + MgH2 reactive hydride composite system was attempted aiming to obtain a full reversible system with the simultaneous suppression of CaB12H12.,Structural characterization of the specimens was performed by means of in-situ Synchrotron Radiation Powder X-ray diffraction (SR-PXD) and 11B{1H} Solid State Magic Angle Spinning-Nuclear Magnetic Resonance (MAS-NMR). The evolution of the chemical state of the Nb- and Ti-based additives was monitored by X-ray Absorption Near Edge Structure (XANES).,The addition of NbF5 or TiF4 to the Ca(BH4)2 + MgH2 system have not suppressed completely the formation of CaB12H12 and only a slight improvement concerning the reversible reaction was displayed just in the case of Nb-doped composite material. %0 journal article %@ 1932-7447 %A Pistidda, C.,Santoru, A.,Garroni, S.,Bergemann, N.,Rzeszutek, A.,Horstmann, C.,Thomas, D.,Klassen, T.,Dornheim, M. %D 2015 %J The Journal of Physical Chemistry C %N 2 %P 934-943 %R doi:10.1021/jp510720x %T First Direct Study of the Ammonolysis Reaction in the Most Common Alkaline and Alkaline Earth Metal Hydrides by in Situ SR-PXD %U https://doi.org/10.1021/jp510720x 2 %X We report on the first in situ synchrotron radiation powder X-ray diffraction study (SR-PXD) of the ammonolysis reaction of selected alkaline and alkaline earth metal hydrides (i.e., LiH, NaH, KH, MgH2, and CaH2). The investigation was performed using an in situ SR-PXD pressure cell at an initial NH3 pressure of 6.5 bar in a range of temperature between room temperature (RT) and 350 °C. The results of this work give new important insights into the formation of metal amides and imides starting from the corresponding metal hydrides. LiH was observed to react with NH3 to form LiNH2 already at RT, and then it decomposes into Li2NH at 310 °C through the formation of nonstoichiometric intermediates of the Li1+xNH2–x form. The formation of NaNH2 takes place nearly at RT (28 °C), and it melts at 180 °C. As for LiH, KH reacts with NH3 at RT to surprisingly form, what it seems to be, cubic KNH2. However, we believe this phase to be a solid solution of KH in KNH2. At high temperature, the possible formation of several solid solutions of K(NH2)1–yHy with defined composition is also observed. The formation of Mg(NH2)2 was observed to starts at around 220 °C, from the interaction γ-MgH2 and NH3. At 350 °C, when all γ-MgH2 is consumed, the formation of Mg(NH2)2 stops and MgNH is formed by the reaction between β-MgH2 and NH3. Our results indicate that the formation of the γ-MgH2 is a key step in the synthesis of Mg(NH2)2 at low temperature (e.g., via ball milling technique). CaH2 was observed to react with NH3 at around 140 °C to form CaNH. At higher temperature the appearance of new reflections of possible Ca1+xNH phases, with the same crystalline structure of CaNH but with a smaller cell parameter was observed. %0 journal article %@ 0925-8388 %A Busch, N.,Jepsen, J.,Pistidda, C.,Puszkiel, J.A.,Karimi, F.,Milanese, C.,Tolkiehn, M.,Chaudhary, A.-L.,Klassen, T.,Dornheim, M. %D 2015 %J Journal of Alloys and Compounds %N S 1 %P S299-S303 %R doi:10.1016/j.jallcom.2014.12.187 %T Influence of milling parameters on the sorption properties of the LiH-MgB2 system doped with TiCl3 %U https://doi.org/10.1016/j.jallcom.2014.12.187 S 1 %X Hydrogen sorption properties of the LiH–MgB2 system doped with TiCl3 were investigated with respect to milling conditions (milling times, ball to powder (BTP) ratios, rotation velocities and degrees of filling) to form the reactive hydride composite (RHC) LiBH4–MgH2. A heuristic model was applied to approximate the energy transfer from the mill to the powders. These results were linked to experimentally obtained quantities such as crystallite size, specific surface area (SSA) and homogeneity of the samples, using X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method and scanning electron microscopy (SEM), respectively. The results show that at approximately 20 kJ g−1 there are no further benefits to the system with an increase in energy transfer. This optimum energy transfer value indicates that a plateau was reached for MgB2 crystallite size therefore the there was also no improvement of reaction kinetics due to no change in crystallite size. Therefore, this study shows that an optimum energy transfer value was reached for the LiH–MgB2 system doped with TiCl3. %0 journal article %@ 0360-3199 %A Bellosta von Colbe, J.M.,Lozano, G.,Metz, O.,Buecherl, T.,Bormann, R.,Klassen, T.,Dornheim, M. %D 2015 %J International Journal of Hydrogen Energy %N 7 %P 2984-2988 %R doi:10.1016/j.ijhydene.2015.01.013 %T Design, sorption behaviour and energy management in a sodium alanate-based lightweight hydrogen storage tank %U https://doi.org/10.1016/j.ijhydene.2015.01.013 7 %X A lightweight tank for hydrogen storage based on four kilograms of sodium alanate was designed, built and tested. An improvement in gravimetric capacity of 83% and 49% in volumetric capacity over a previous tank [1] was achieved. Heat evolution and temperature spikes during hydrogen absorption were studied. Due to the high specific heat of the complex hydride, the storage material itself acts as a heat sink, aiding in the heat management of the system. The first-ever radiography with fast neutrons on an operational complex-hydride based test tank was performed. %0 journal article %@ 1864-5631 %A Cao, H.,Richter, T.M.M.,Pistidda, C.,Chaudhary, A.-L.,Santoru, A.,Gizer, G.,Niewa, R.,Chen, P.,Klassen, T.,Dornheim, M. %D 2015 %J ChemSusChem %N 22 %P 3777-3782 %R doi:10.1002/cssc.201500990 %T Ternary Amides Containing Transition Metals for Hydrogen Storage: A Case Study with Alkali Metal Amidozincates %U https://doi.org/10.1002/cssc.201500990 22 %X The alkali metal amidozincates Li4[Zn(NH2)4](NH2)2 and K2[Zn(NH2)4] were, to the best of our knowledge, studied for the first time as hydrogen storage media. Compared with the LiNH2–2 LiH system, both Li4[Zn(NH2)4](NH2)2–12 LiH and K2[Zn(NH2)4]–8 LiH systems showed improved rehydrogenation performance, especially K2[Zn(NH2)4]–8 LiH, which can be fully hydrogenated within 30 s at approximately 230 °C. The absorption properties are stable upon cycling. This work shows that ternary amides containing transition metals have great potential as hydrogen storage materials. %0 journal article %@ 1463-9076 %A Karimi, F.,Pranzas, P.K.,Pistidda, C.,Puszkiel, J.A.,Milanese, C.,Vainio, U.,Paskevicius, M.,Emmler, T.,Santoru, A.,Utke, R.,Tolkiehn, M.,Minella, C.B.,Chaudhary, A.-L.,Boerries, S.,Buckley, C.E.,Enzo, S.,Schreyer, A.,Klassen, T.,Dornheim, M. %D 2015 %J Physical Chemistry Chemical Physics %N 41 %P 27328-27342 %R doi:10.1039/c5cp03557k %T Structural and kinetic investigation of the hydride composite Ca(BH4)2 + MgH2 system doped with NbF5 for solid-state hydrogen storage %U https://doi.org/10.1039/c5cp03557k 41 %X Designing safe, compact and high capacity hydrogen storage systems is the key step towards introducing a pollutant free hydrogen technology into a broad field of applications. Due to the chemical bonds of hydrogen–metal atoms, metal hydrides provide high energy density in safe hydrogen storage media. Reactive hydride composites (RHCs) are a promising class of high capacity solid state hydrogen storage systems. Ca(BH4)2 + MgH2 with a hydrogen content of 8.4 wt% is one of the most promising members of the RHCs. However, its relatively high desorption temperature of ∼350 °C is a major drawback to meeting the requirements for practical application. In this work, by using NbF5 as an additive, the dehydrogenation temperature of this RHC was significantly decreased. To elucidate the role of NbF5 in enhancing the desorption properties of the Ca(BH4)2 + MgH2 (Ca-RHC), a comprehensive investigation was carried out via manometric measurements, mass spectrometry, Differential Scanning Calorimetry (DSC), in situ Synchrotron Radiation-Powder X-ray Diffraction (SR-PXD), X-ray Absorption Spectroscopy (XAS), Anomalous Small-Angle X-ray Scattering (ASAXS), Scanning and Transmission Electron Microscopy (SEM, TEM) and Nuclear Magnetic Resonance (NMR) techniques. %0 journal article %@ 0168-9002 %A Boerries, S.,Metz, O.,Pranzas, P.K.,Buecherl, T.,Soellradl, S.,Dornheim, M.,Klassen, T.,Schreyer, A. %D 2015 %J Nuclear Instruments and Methods in Physics Research A %N %P 158-164 %R doi:10.1016/j.nima.2015.06.033 %T Scattering influences in quantitative fission neutron radiography for the in situ analysis of hydrogen distribution in metal hydrides %U https://doi.org/10.1016/j.nima.2015.06.033 %X In situ neutron radiography allows for the time-resolved study of hydrogen distribution in metal hydrides. However, for a precise quantitative investigation of a time-dependent hydrogen content within a host material, an exact knowledge of the corresponding attenuation coefficient is necessary. Additionally, the effect of scattering has to be considered as it is known to violate Beer׳s law, which is used to determine the amount of hydrogen from a measured intensity distribution. Within this study, we used a metal hydride inside two different hydrogen storage tanks as host systems, consisting of steel and aluminum. The neutron beam attenuation by hydrogen was investigated in these two different setups during the hydrogen absorption process. A linear correlation to the amount of absorbed hydrogen was found, allowing for a readily quantitative investigation. Further, an analysis of scattering contributions on the measured intensity distributions was performed and is described in detail. %0 journal article %@ 0003-6951 %A Chaudhary, A.-L.,Li, G.,Matsuo, M.,Orimo, S.,Deledda, S.,Soerby, M.H.,Hauback, B.C.,Pistidda, C.,Klassen, T.,Dornheim, M. %D 2015 %J Applied Physics Letters %N 7 %P 073905 %R doi:10.1063/1.4929340 %T Simultaneous desorption behavior of M borohydrides and Mg2FeH6 reactive hydride composites (M = Mg, then Li, Na, K, Ca) %U https://doi.org/10.1063/1.4929340 7 %X Combinations of complex metal borohydrides ball milled with the transition metal complex hydride, Mg2FeH6, are analysed and compared. Initially, the Reactive Hydride Composite (RHC) of Mg2+ cation mixtures of Mg2FeH6 and γ-Mg(BH4)2 is combined in a range of molar ratios and heated to a maximum of 450 °C. For the molar ratio of 6 Mg2FeH6 + Mg(BH4)2, simultaneous desorption of the two hydrides occurred, which resulted in a single event of hydrogen release. This single step desorption occurred at temperatures between those of Mg2FeH6 and γ-Mg(BH4)2. Keeping this anionic ratio constant, the desorption behavior of four other borohydrides, Li-, Na-, K-, and Ca-borohydrides was studied by using materials ball milled with Mg2FeH6 applying the same milling parameters. The mixtures containing Mg-, Li-, and Ca-borohydrides also released hydrogen in a single event. The Mass Spectrometry (MS) results show a double step reaction within a narrow temperature range for both the Na- and K-borohydride mixtures. This phenomenon, observed for the RHC systems at the same anionic ratio with all five light metal borohydride mixtures, can be described as simultaneous hydrogen desorption within a narrow temperature range centered around 300 °C. %0 journal article %@ 0378-7753 %A Puszkiel, J.A.,Gennari, F.C.,Larochette, P.A.,Ramallo-Lopez, J.M.,Vainio, U.,Karimi, F.,Pranzas, P.K.,Troiani, H.,Pistidda, C.,Jepsen, J.,Tolkiehn, M.,Welter, E.,Klassen, T.,Bellosta von Colbe, J.,Dornheim, M. %D 2015 %J Journal of Power Sources %N %P 606-616 %R doi:10.1016/j.jpowsour.2015.02.153 %T Effect of Fe additive on the hydrogenation-dehydrogenation properties of 2LiH + MgB2/2LiBH4 + MgH2 system %U https://doi.org/10.1016/j.jpowsour.2015.02.153 %X Lithium reactive hydride composite 2LiBH4 + MgH2 (Li-RHC) has been lately investigated owing to its potential as hydrogen storage medium for mobile applications. However, the main problem associated with this material is its sluggish kinetic behavior. Thus, aiming to improve the kinetic properties, in the present work the effect of the addition of Fe to Li-RHC is investigated. The addition of Fe lowers the starting decomposition temperature of Li-RHC about 30 °C and leads to a considerably faster isothermal dehydrogenation rate during the first hydrogen sorption cycle. Upon hydrogenation, MgH2 and LiBH4 are formed whereas Fe appears not to take part in any reaction. Upon the first dehydrogenation, the formation of nanocrystalline, well distributed FeB reduces the overall hydrogen storage capacity of the system. Throughout cycling, the agglomeration of FeB particles causes a kinetic deterioration. An analysis of the hydrogen kinetic mechanism during cycling shows that the hydrogenation and dehydrogenation behavior is influenced by the activity of FeB as heterogeneous nucleation center for MgB2 and its non-homogenous distribution in the Li-RHC matrix. %0 journal article %@ 0925-8388 %A Torre, F.,Valentoni, A.,Milanese, C.,Pistidda, C.,Marini, A.,Dornheim, M.,Enzo, S.,Mulas, G.,Garroni, S. %D 2015 %J Journal of Alloys and Compounds %N 1 %P S 284-S 287 %R doi:10.1016/j.jallcom.2014.12.228 %T Kinetic improvement on the CaH2-catalyzed Mg(NH2)2 + 2LiH system %U https://doi.org/10.1016/j.jallcom.2014.12.228 1 %X In the present work we focused on the catalytic effect of CaH2 on the dehydrogenation process of the Mg(NH2)2–2LiH system. The synthesis, hydrogen storage properties and energy barriers were investigated by X-ray diffraction (XRD), temperature-programmed desorption (TPD) and differential scanning calorimetry (DSC). The TPD measurements proved that desorption of the Mg(NH2)2–2LiH system milled with 0.08 mol of CaH2 started at temperature of 78 °C, lower if compared with the 125 °C observed in the pristine material. Furthermore, Kissinger analysis revealed that CaH2 acted as a catalyst to decrease the activation energy of the first dehydrogenation step from a value of 133.8 ± 4.1 kJ/mol for the pristine material to 105.1 ± 3.2 kJ/mol when CaH2 was dispersed into the mixture. %0 journal article %@ 0360-3199 %A Pistidda, C.,Pottmaier, D.,Karimi, F.,Garroni, S.,Rzeszutek, A.,Tolkiehn, M.,Fichtner, M.,Lohstroh, W.,Baricco, M.,Klassen, T.,Dornheim, M. %D 2014 %J International Journal of Hydrogen Energy %N 10 %P 5030-5036 %R doi:10.1016/j.ijhydene.2014.01.105 %T Effect of NaH/MgB2 ratio on the hydrogen absorption kinetics of the system NaH + MgB2 %U https://doi.org/10.1016/j.ijhydene.2014.01.105 10 %X In this work the effect of the ratio of starting reactants on the hydrogen absorption reaction of the system xNaH + MgB2 is investigated. At a constant hydrogen pressure of 50 bar, depending on the amount of NaH present in the system NaH + MgB2, different hydrogen absorption behaviors are observed. For two system compositions: NaH + MgB2 and 0.5NaH + MgB2, the formation of NaBH4 and MgH2 as only crystalline hydrogenation products is achieved. The relation between the ratio of the starting reactants and the obtained hydrogenation products is discussed in detail. %0 journal article %@ 0925-8388 %A Soru, S.,Taras, A.,Pistidda, C.,Milanese, C.,Bonatto Minella, C.,Masolo, E.,Nolis, P.,Baro, M.D.,Marini, A.,Tolkiehn, M.,Dornheim, M.,Enzo, S.,Mulas, G.,Garroni, S. %D 2014 %J Journal of Alloys and Compounds %N S1 %P S 693-S 697 %R doi:10.1016/j.jallcom.2013.12.027 %T Structural evolution upon decomposition of the LiAlH4 + LiBH4 system %U https://doi.org/10.1016/j.jallcom.2013.12.027 S1 %X In the present work we focus the attention on the phase structural transformations occurring upon the desorption process of the LiBH4 + LiAlH4 system. This study is conducted by means of manometric–calorimetric, in situ Synchrotron Radiation Powder X-ray Diffraction (SR-PXD) and exsitu Solid State Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) measurements. The desorption reaction is characterized by two main dehydrogenation steps starting at 320 and 380 °C, respectively. The first step corresponds to the decomposition of LiAlH4 into Al and H2via the formation of Li3AlH6 whereas the second one refers to the dehydrogenation of LiBH4 (molten state). In the range 328–380 °C, the molten LiBH4 reacts with metallic Al releasing hydrogen and forming an unidentified phase which appears to be an important intermediate for the desorption mechanism of LiBH4–Al-based systems. Interestingly, NMR studies indicate that the unknown intermediate is stable up to 400 °C and it is mainly composed of Li, B, Al and H. In addition, the NMR measurements of the annealed powders (400 °C) confirm that the desorption reaction of the LiBH4 + Al system proceeds via an amorphous boron compound. %0 journal article %@ 0021-8898 %A Karimi, F.,Pranzas, P.K.,Hoell, A.,Vainio, U.,Welter, E.,Raghuwanshi, V.S.,Pistidda, C.,Dornheim, M.,Klassen, T.,Schreyer, A. %D 2014 %J Journal of Applied Crystallography %N 1 %P 67-75 %R doi:10.1107/S1600576713031567 %T Structural analysis of calcium reactive hydride composite for solid state hydrogen storage %U https://doi.org/10.1107/S1600576713031567 1 %X Owing to a theoretical hydrogen storage capacity of 10.5 wt% H2, Ca(BH4)2+MgH2, the so-called calcium reactive hydride composite (Ca-RHC), has a great potential as a hydrogen storage material. However, its dehydrogenation temperature (623 K) is too high for any mobile applications. By addition of 10 mol% of NbF5 into Ca(BH4)2+MgH2, a decrease of the dehydrogenation onset temperature by 120 K is observed. In order to understand the reasons behind this desorption temperature decrement two sets of samples [Ca(BH4)2+MgH2 and Ca(BH4)2+MgH2+0.1NbF5] in different hydrogenation states, were prepared. The structural investigation of the above mentioned sets of samples by means of volumetric measurements, anomalous small-angle X-ray scattering (ASAXS) and X-ray absorption spectroscopy (XAS) is reported here. The XAS results show that after the milling procedure NbB2 is formed and remains stable upon further de/rehydrogenation cycling. The results of Nb ASAXS point to nanometric spherical NbB2 particles distributed in the hydride matrix, with a mean diameter of 10 nm. Results from Ca ASAXS indicate Ca-containing nanostructures in the Ca-RHC+0.1NbF5 samples to be 50% finer compared to those without additive. Thus, a higher reaction surface area and shorter diffusion paths for the constituents are concluded to be important contributions to the catalytic effect of an NbF5 additive on the hydrogen sorption kinetics of the Ca(BH4)2+MgH2 composite system. %0 journal article %@ 0360-3199 %A Boesenberg, U.,Pistidda, C.,Tolkiehn, M.,Busch, N.,Saldan, I.,Suarez-Alcantara, K.,Arendarska, A.,Klassen, T.,Dornheim, M. %D 2014 %J International Journal of Hydrogen Energy %N 18 %P 9899-9903 %R doi:10.1016/j.ijhydene.2014.02.068 %T Characterization of metal hydrides by in-situ XRD %U https://doi.org/10.1016/j.ijhydene.2014.02.068 18 %X In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) technique is a powerful tool to gain a deeper understanding of reaction mechanisms in crystalline materials. In this paper, the implementation of a new in-situ SR-PXD cell for solid–gas reactions is described in detail. The cell allows performing measurements in a range of pressure which goes from light vacuum (10−2 bar) up to 200 bar and temperatures from room temperature up to 550 °C. The high precision, with which pressure and temperature are measured, enables to estimate the thermodynamic properties of the observed changes in the crystal structure and phase transformations. %0 journal article %@ 1369-7021 %A Ley, M.B.,Jepsen, L.H.,Lee, Y.-S.,Cho, Y.W.,Bellosta von Colbe, J.M.,Dornheim, M.,Rokni, M.,jensen, J.O.,Sloth, M.,Filinchuk, Y.,Joergensen, J.E.,Besenbacher, F.,Jensen, T.R. %D 2014 %J Materials Today %N 3 %P 122-128 %R doi:10.1016/j.mattod.2014.02.013 %T Complex hydrides for hydrogen storage – New perspectives %U https://doi.org/10.1016/j.mattod.2014.02.013 3 %X Since the 1970s, hydrogen has been considered as a possible energy carrier for the storage of renewable energy. The main focus has been on addressing the ultimate challenge: developing an environmentally friendly successor for gasoline. This very ambitious goal has not yet been fully reached, as discussed in this review, but a range of new lightweight hydrogen-containing materials has been discovered with fascinating properties. State-of-the-art and future perspectives for hydrogen-containing solids will be discussed, with a focus on metal borohydrides, which reveal significant structural flexibility and may have a range of new interesting properties combined with very high hydrogen densities. %0 journal article %@ 0360-3199 %A Napolitano, E.,Dolci, F.,Campesi, R.,Pistidda, C.,Hoelzel, M.,Moretto, P.,Enzo, S. %D 2014 %J International Journal of Hydrogen Energy %N 2 %P 868-876 %R doi:10.1016/j.ijhydene.2013.10.131 %T Crystal structure solution of KMg(ND)(ND2): An ordered mixed amide/imide compound %U https://doi.org/10.1016/j.ijhydene.2013.10.131 2 %X An ordered mixed deuterated amide/imide potassium–magnesium compound was synthesized with the intent of solving its structure using neutron diffraction technique with help of “ab-initio” methods. Obtained powder diffraction patterns were compatible with the orthorhombic P212121 space group, and lattice parameters a = 9.8896(3) Å; b = 9.3496(3) Å; c = 3.6630(1) Å, respectively.,Assuming a density of 1.91 g/cm3 the investigation has allowed to locate the four constituting elements distributed in seven different sites into Wyckoff general positions 4(a), for a total of 28 atoms in the unit cell. This is the first example of crystal structure solution of a mixed imide/amide compound appearing during the dehydrogenation process of a potassium containing amide based hydrogen storage material. %0 journal article %@ 1438-1656 %A Boehme, B.,Bonatto Minella, C.,Thoss, F.,Lindemann, I.,Rosenburg, M.,Pistidda, C.,Moeller, K.T.,Jensen, T.R.,Giebeler, L.,Baitinger, M.,Gutfleisch, O.,Ehrenberg, H.,Eckert, J.,Grin, Y.,Schultz, L. %D 2014 %J Advanced Engineering Materials %N 10 %P 1189-1195 %R doi:10.1002/adem.201400182 %T B1-Mobilstor: Materials for Sustainable Energy Storage Techniques – Lithium Containing Compounds for Hydrogen and Electrochemical Energy Storage %U https://doi.org/10.1002/adem.201400182 10 %X New material concepts for hydrogen storage and lithium ion batteries are investigated in the joint ECEMP project B1 – Mobilstor. Chemical composition are essential for the performance of a storage material. A certain state of material can be effectively analyzed by in situ methods to obtain a maximum of information. For hydrogen storage the LiNH2[BOND]MgH2 system and as lithium ion battery anode the Ge(cF136) allotrop are highlighted under this issue. %0 journal article %@ 1932-7447 %A Pistidda, C.,Karimi, F.,Garroni, S.,Rzeszutek, A.,Bonatto Minella, C.,Milanese, C.,Le, T.T.,Rude, L.H.,Skibsted, J.,Jensen, T.R.,Horstmann, C.,Gundlach, C.,Tolkiehn, M.,Pranzas, P.K.,Schreyer, A.,Klassen, T.,Dornheim, M. %D 2014 %J The Journal of Physical Chemistry C %N 49 %P 28409-28417 %R doi:10.1021/jp508780b %T Effect of the Partial Replacement of CaH2 with CaF2 in the Mixed System CaH2 + MgB2 %U https://doi.org/10.1021/jp508780b 49 %X In this work the effect of a partial replacement of CaH2 with CaF2 on the sorption properties of the system CaH2 + MgB2 has been studied. The first five hydrogen absorption and four desorption reactions of the CaH2 + MgB2 and 3CaH2 + CaF2 + 4MgB2 systems were investigated by means of volumetric measurements, high-pressure differential scanning calorimetric technique (HP-DSC), 11B and 19F MAS NMR spectroscopy, and in situ synchrotron radiation powder X-ray diffraction (SR-PXD). It was observed that already during the mixing of the reactants formation of a nonstoichiometric CaF2–xHx solid solution takes place. Formation of the CaF2–xHx solid solution sensibly affects the overall hydrogen sorption reactions of the system CaH2 + MgB2. %0 journal article %@ 0360-3199 %A Gosalawit-Utke, R.,Thiangviriya, S.,Javadian, P.,Laipple, D.,Pistidda, C.,Bergemann, N.,Horstmann, C.,Jensen, T.R.,Klassen, T.,Dornheim, M. %D 2014 %J International Journal of Hydrogen Energy %N 28 %P 15614-15626 %R doi:10.1016/j.ijhydene.2014.07.167 %T Effective nanoconfinement of 2LiBH4–MgH2 via simply MgH2 premilling for reversible hydrogen storages %U https://doi.org/10.1016/j.ijhydene.2014.07.167 28 %X To improve nanoconfinement of LiBH4 and MgH2 in carbon aerogel scaffold (CAS), particle size reduction of MgH2 by premilling technique before melt infiltration is proposed. MgH2 is premilled for 5 h prior to milling with LiBH4 and nanoconfinement in CAS to obtained nanoconfined 2LiBH4–premilled MgH2. Significant confinement of both LiBH4 and MgH2 in CAS, confirmed by SEM–EDS–mapping results, is achieved due to MgH2 premilling. Due to effective nanoconfinement, enhancement of CAS:hydride composite weight ratio to 1:1, resulting in increase of hydrogen storage capacity, is possible. Nanoconfined 2LiBH4–premilled MgH2 reveals a single–step dehydrogenation at 345 °C with no B2H6 release, while dehydrogenation of nanoconfined sample without MgH2 premilling performs in multiple steps at elevated temperatures (up to 430 °C) together with considerable amount of B2H6 release. Activation energy (EA) for the main dehydrogenation of nanoconfined 2LiBH4–premilled MgH2 is considerably lower than those of LiBH4 and MgH2 of bulk 2LiBH4–MgH2 (ΔEA = 31.9 and 55.8 kJ/mol with respect to LiBH4 and MgH2, respectively). Approximately twice faster dehydrogenation rate are accomplished after MgH2 premilling. Three hydrogen release (T = 320 °C, P(H2) = 3–4 bar) and uptake (T = 320–325 °C, P(H2) = 84 bar) cycles of nanoconfined 2LiBH4–premilled MgH2 reveal up to 4.96 wt. % H2 (10 wt. % H2 with respect to hydride composite content), while the 1st desorption of nanoconfined sample without MgH2 premilling gives 4.30 wt. % of combined B2H6 and H2 gases. It should be remarked that not only kinetic improvement and B2H6 suppression are obtained by MgH2 premilling, but also the lowest dehydrogenation temperature (T = 320 °C) among other modified 2LiBH4–MgH2 systems is acquired. %0 journal article %@ 0360-3199 %A Gosalawit-Utke, R.,Meethom, S.,Pistidda, C.,Milanese, C.,Laipple, D.,Saisopa, T.,Marini, A.,Klassen, T.,Dornheim, M. %D 2014 %J International Journal of Hydrogen Energy %N 10 %P 5019-5029 %R doi:10.1016/j.ijhydene.2014.01.078 %T Destabilization of LiBH4 by nanoconfinement in PMMA–co–BM polymer matrix for reversible hydrogen storage %U https://doi.org/10.1016/j.ijhydene.2014.01.078 10 %X Destabilization of LiBH4 by nanoconfinement in poly (methyl methacrylate)–co–butyl methacrylate (PMMA–co–BM), denoted as nano LiBH4–PMMA–co–BM, is proposed for reversible hydrogen storage. The onset dehydrogenation temperature of nano LiBH4–PMMA–co–BM is reduced to ∼80 °C (ΔT = 340 and 170 °C as compared with milled LiBH4 and nanoconfined LiBH4 in carbon aerogel, respectively). At 120 °C under vacuum, nano LiBH4–PMMA–co–BM releases 8.8 wt.% H2 with respect to LiBH4 content within 4 h during the 1st dehydrogenation, while milled LiBH4 performs no dehydrogenation at the same temperature and pressure condition. Moreover, nano LiBH4–PMMA–co–BM can be rehydrogenated at the mildest condition (140 °C under 50 bar H2 for 12 h) among other modified LiBH4 reported in the previous literature. Due to the hydrophobicity of PMMA–co–BM host, deterioration of LiBH4 by oxygen and humidity in ambient condition is avoided after nanoconfinement. Although the interaction between LiBH4 and the pendant group of PMMA–co–BM leads to a reduced hydrogen storage capacity, significant destabilization of LiBH4 is accomplished. %0 journal article %@ 0378-7753 %A Puszkiel, J.,Gennari, F.C.,Larochette, P.A.,Troiani, H.E.,Karimi, F.,Pistidda, C.,Gosalawit-Utke, R.,Jepsen, J.,Jensen, T.R.,Gundlach, C.,Tolkiehn, M.,Bellosta von Colbe, J.,Klassen, T.,Dornheim, M. %D 2014 %J Journal of Power Sources %N %P 799-811 %R doi:10.1016/j.jpowsour.2014.05.130 %T Hydrogen storage in Mg–LiBH4 composites catalyzed by FeF3 %U https://doi.org/10.1016/j.jpowsour.2014.05.130 %X Mg–10 mol% LiBH4 composite plus small amounts of FeF3 is investigated in the present work. The presence of LiBH4 during the milling process noticeably modifies the size and morphology of the Mg agglomerates, leading to faster hydrogenation and reaching almost the theoretical hydrogen capacity owing to enhanced hydrogen diffusion mechanism. However, the dehydrogenation of the system at low temperatures (≤300 °C) is still slow. Thus, FeF3 addition is proposed to improve the dehydrogenation kinetic behavior. From experimental results, it is found that the presence of FeF3 results in an additional size reduction of the Mg agglomerates between ∼10 and ∼100 μm and the formation of stable phases such as MgF2, LiF and FeB. The FeB species might have a catalytic effect upon the MgH2 decomposition. As a further result of the FeF3 addition, the Mg–10 mol%LiBH4–5 mol% FeF3 material shows improved dehydrogenation properties: reduced dehydrogenation activation energy, faster hydrogen desorption rate and reversible hydrogen capacities of about 5 wt% at 275 °C. %0 journal article %@ 0378-7753 %A Pistidda, C.,Bergemann, N.,Wurr, J.,Rzeszutek, A.,Moeller, K.T.,Hansen, B.R.S.,Garroni, S.,Horstmann, C.,Milanese, C.,Girella, A.,Metz, O.,Taube, K.,Jensen, T.R.,Thomas, D.,Liermann, H.P.,Klassen, T.,Dornheim, M. %D 2014 %J Journal of Power Sources %N %P 554-563 %R doi:10.1016/j.jpowsour.2014.07.129 %T Hydrogen storage systems from waste Mg alloys %U https://doi.org/10.1016/j.jpowsour.2014.07.129 %X The production cost of materials for hydrogen storage is one of the major issues to be addressed in order to consider them suitable for large scale applications. In the last decades several authors reported on the hydrogen sorption properties of Mg and Mg-based systems. In this work magnesium industrial wastes of AZ91 alloy and Mg-10 wt.% Gd alloy are used for the production of hydrogen storage materials. The hydrogen sorption properties of the alloys were investigated by means of volumetric technique, in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and calorimetric methods. The measured reversible hydrogen storage capacity for the alloys AZ91 and Mg-10 wt.% Gd are 4.2 and 5.8 wt.%, respectively. For the Mg-10 wt.% Gd alloy, the hydrogenated product was also successfully used as starting reactant for the synthesis of Mg(NH2)2 and as MgH2 substitute in the Reactive Hydride Composite (RHC) 2LiBH4 + MgH2. The results of this work demonstrate the concrete possibility to use Mg alloy wastes for hydrogen storage purposes. %0 journal article %@ 0360-3199 %A Bergemann, N.,Pistidda, C.,Milanese, C.,Girella, A.,Hansen, B.R.S.,Wurr, J.,Bellosta von Colbe, J.,Jepsen, J.,Jensen, T.R.,Marini, A.,Klassen, T.,Dornheim, M. %D 2014 %J International Journal of Hydrogen Energy %N 18 %P 9877-9882 %R doi:10.1016/j.ijhydene.2014.02.025 %T NaAlH4 production from waste aluminum by reactive ball milling %U https://doi.org/10.1016/j.ijhydene.2014.02.025 18 %X Due to its thermodynamic properties and high reversibility, Ti doped sodium alanate is considered as a prototype hydrogen storage material. In this work we show how sodium alanate can be synthesized by reactive ball milling using aluminum particles obtained from recycled waste incineration slag. The synthesis was monitored with an in situ milling vial and characterized stepwise by PXD and DTA analyses. The sorption properties of the material were investigated using in situ synchrotron radiation PXD and volumetric analyses. A complete conversion of the starting reactants was obtained. %0 journal article %@ 0360-3199 %A Valentoni, A.,Garroni, S.,Pistidda, C.,Masolo, E.,Napolitano, E.,Moretto, P.,Dornheim, M.,Mulas, G.,Enzo, S. %D 2014 %J International Journal of Hydrogen Energy %N 30 %P 17075-17082 %R doi:10.1016/j.ijhydene.2014.07.169 %T New insights into the thermal desorption of the 2LiNH2 + KBH4 + LiH mixture %U https://doi.org/10.1016/j.ijhydene.2014.07.169 30 %X In situ two-dimensional synchrotron X-ray powder diffraction investigation combined with Rietveld method data analysis were performed in order to yield a complete and quantitative phases structure evolution of the polycrystalline mixture 2LiNH2 + KBH4 + LiH during H2 desorption. While a first-principles, purely thermodynamics approach of the system predicted a single dehydrogenation step reaction at relatively low temperatures, it is assessed experimentally that the reaction occurs in two steps with first the formation of Li2NH at ca. 230 °C due to the reaction between LiNH2 and LiH plus hydrogen and ammonia evolution, followed by an additional reaction of the resulting phases with KBH4 at 360 °C, which releases hydrogen and leads to the formation of the monoclinic and tetragonal Li3BN2 polymorphs. Besides pointing out possible limits of a purely thermodynamics approach inevitably relying exact knowledge of experimental quantities, it is concluded that before assuming it viable for on-board vehicle use, additional stoichiometries may be worth of investigation in order to assess any existence of lower hydrogen desorption temperature of such system. %0 journal article %@ 0360-3199 %A Lozano, G.A.,Bellosta von Colbe, J.M.,Klassen, T.,Dornheim, M. %D 2014 %J International Journal of Hydrogen Energy %N 33 %P 18952-18957 %R doi:10.1016/j.ijhydene.2014.09.035 %T Transport phenomena versus intrinsic kinetics: Hydrogen sorption limiting sub-process in metal hydride beds %U https://doi.org/10.1016/j.ijhydene.2014.09.035 33 %X This paper discusses and compares the different sub-processes that occur during the hydrogen sorption of practical systems based on metal hydrides, i.e. intrinsic kinetics, heat transfer and hydrogen transport. Derived from their modeling equations, a resistance analysis is developed on these hydrogen sorption sub-processes for the first time. This analysis allows quantifying how strongly each sub-process affects the overall sorption kinetics in a hydride bed and thereby the sorption-rate limiting sub-process can be identified. It was found that in the case of the hydrogen absorption of sodium alanate material the heat transfer resistance is the dominant and rate limiting sub-process, with the exception of small geometries. Besides, the resistance due to hydrogen transport is negligible in comparison to the overall absorption resistance. As a consequence, simulations and designs of scaled-up systems based on sodium alanate material always require heat transfer optimization as one of the foremost considerations. %0 journal article %@ 1932-7447 %A Bonatto Minella, C.,Pistidda, C.,Garroni, S.,Nolis, P.,Baro, M.D.,Gutfleisch, O.,Klassen, T.,Bormann, R.,Dornheim, M. %D 2013 %J The Journal of Physical Chemistry C %N 8 %P 3846-3852 %R doi:10.1021/jp312271s %T Ca(BH4)2 + MgH2: Desorption Reaction and Role of Mg on Its Reversibility %U https://doi.org/10.1021/jp312271s 8 %X The Ca(BH4)2–MgH2 composite system represents a promising candidate for mobile hydrogen storage due to a 10.5 wt % theoretical hydrogen storage capacity and an estimated equilibrium temperature lower than 160 °C. For this system, the reversibility was achieved without further addition of additives. In this study, the decomposition path of the Ca(BH4)2 + MgH2 composite system is investigated in detail by in situ synchrotron radiation powder X-ray diffraction and differential scanning calorimetry combined with thermogravimetry. The sorption properties are analyzed by volumetric measurements. 11B{1H} solid state magic angle spinning–nuclear magnetic resonance was employed for the characterization of the final amorphous or nanocrystalline boron-based decomposition products. This study shows that the intermediate formation of Ca4Mg3H14 upon dehydrogenation of the Ca(BH4)2–MgH2 composite system is not a necessary step, and its presence can be adjusted modifying the preparation procedure. Moreover, the d-value mismatch calculated for the {111}CaB6/{1011}Mg plane pair is the lowest among the other plane pairs considered in the system. The mismatch in the third direction between CaB6 and Mg is also extremely good. These findings propose Mg as a supporter of the heterogeneous nucleation of CaB6 during decomposition of the Ca(BH4)2 + MgH2 composite system. %0 journal article %@ 0360-3199 %A Puszkiel, J.,Gennari, F.,Larochette, P.A.,Karimi, F.,Pistidda, C.,Gosalawit-Utke, R.,Jepsen, J.,Jensen, T.R.,Gundlach, C.,Bellosta von Colbe, J.,Klassen, T.,Dornheim, M. %D 2013 %J International Journal of Hydrogen Energy %N 34 %P 14618-14630 %R doi:10.1016/j.ijhydene.2013.08.068 %T Sorption behavior of the MgH2–Mg2FeH6 hydride storage system synthesized by mechanical milling followed by sintering %U https://doi.org/10.1016/j.ijhydene.2013.08.068 34 %X The hydrogen sorption behavior of the Mg2FeH6–MgH2 hydride system is investigated via in-situ synchrotron and laboratory powder X-ray diffraction (SR-PXD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), particle size distribution (PSD) and volumetric techniques. The Mg2FeH6–MgH2 hydride system is obtained by mechanical milling in argon atmosphere followed by sintering at high temperature and hydrogen pressure. In-situ SR-PXD results show that upon hydriding MgH2 is a precursor for Mg2FeH6 formation and remained as hydrided phase in the obtained material. Diffusion constraints preclude the further formation of Mg2FeH6. Upon dehydriding, our results suggest that MgH2 and Mg2FeH6 decompose independently in a narrow temperature range between 275 and 300 °C. Moreover, the decomposition behavior of both hydrides in the Mg2FeH6–MgH2 hydride mixture is influenced by each other via dual synergetic-destabilizing effects. The final hydriding/dehydriding products and therefore the kinetic behavior of the Mg2FeH6–MgH2 hydride system exhibits a strong dependence on the temperature and pressure conditions. %0 journal article %@ 1932-7447 %A Bonatto Minella, C.,Pellicer, E.,Rossinyol, E.,Karimi, F.,Pistidda, C.,Garroni, S.,Milanese, C.,Nolis, P.,Baro, M.D.,Gutfleisch, O.,Pranzas, K.P.,Schreyer, A.,Klassen, T.,Bormann, R.,Dornheim, M. %D 2013 %J The Journal of Physical Chemistry C %N 9 %P 4394-4403 %R doi:10.1021/jp3116275 %T Chemical State, Distribution, and Role of Ti- and Nb-Based Additives on the Ca(BH4)2 System %U https://doi.org/10.1021/jp3116275 9 %X Light metal tetrahydroborates are regarded as promising materials for solid state hydrogen storage. Due to both a high gravimetric hydrogen capacity of 11.5 wt % and an ideal dehydrogenation enthalpy of 32 kJ mol–1 H2, Ca(BH4)2 is considered to be one of the most interesting compounds in this class of materials. In this work, a comprehensive investigation of the effect of different selected additives (TiF4, NbF5, Ti-isopropoxide, and CaF2) on the reversible hydrogenation reaction of calcium borohydride is presented combining different investigation techniques. The chemical state of the Nb- and Ti-based additives is studied by X-ray absorption spectroscopy (e.g., XANES). Transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDX) was used to show the local structure, size, and distribution of the additive/catalyst. 11B{1H} solid state magic angle spinning-nuclear magnetic resonance (MAS NMR) was carried out to detect possible amorphous phases. The formation of TiB2 and NbB2 nanoparticles was observed after milling or upon sorption reactions of the Nb- and Ti-based Ca(BH4)2 doped systems. The formation of transition-metal boride nanoparticles is proposed to support the heterogeneous nucleation of CaB6. The {111}CaB6/{1011}NbB2, {111}CaB6/{1010}NbB2, as well as {111}CaB6/{1011}TiB2 plane pairs have the potential to be the matching planes because the d-value mismatch is well below the d-critical mismatch value (6%). Transition-metal boride nanoparticles act as heterogeneous nucleation sites for CaB6, refine the microstructure thus improving the sorption kinetics, and, as a consequence, lead to the reversible formation of Ca(BH4)2. %0 journal article %@ 0360-3199 %A Garroni, S.,Bonatto Minalla, C.,Pottmaier, D.,Pistidda, C.,Milanese, C.,Marini, A.,Enzo, S.,Mulas, G.,Dornheim, M.,Baricco, M.,Gutfleisch, O.,Surinach, S.,Baro, M.D. %D 2013 %J International Journal of Hydrogen Energy %N 5 %P 2363-2369 %R doi:10.1016/j.ijhydene.2012.11.136 %T Mechanochemical synthesis of NaBH4 starting from NaHMgB2 reactive hydride composite system %U https://doi.org/10.1016/j.ijhydene.2012.11.136 5 %X The present investigation focuses on a new synthesis route of NaBH4 starting from the 2NaH + MgB2 system subjected to mechanochemical activation under reactive hydrogen atmosphere. The milling process was carried out under two different hydrogen pressures (1 and 120 bar) with two different rotation speeds (300 and 550 rpm). The reaction products were characterized by ex-situ solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR), ex-situ X-ray powder diffraction (XRPD) and Infrared Spectroscopy (IR). From the results of these analyses, it can be concluded that milling in all the considered conditions led to the formation of NaBH4 (cubic-Fm-3m). In particular, a reaction yield of 5 and 14 wt% is obtained after 20 h of milling at 120 bar of H2 for the tests performed at 300 rpm and 550 rpm, respectively. The presence of MgH2 is also detected among the final products on the as milled powders. The influence of the milling conditions and the evaluation of the parameters related the mechanochemical process are here discussed. %0 journal article %@ 0360-3199 %A Jepsen, J.,Milanese, C.,Girella, A.,Lozano, G.A.,Pistidda, C.,Bellosta von Colbe, J.M.,Marini, A.,Klassen, T.,Dornheim, M. %D 2013 %J International Journal of Hydrogen Energy %N 20 %P 8357-8366 %R doi:10.1016/j.ijhydene.2013.04.090 %T Compaction pressure influence on material properties and sorption behaviour of LiBH4–MgH2 composite %U https://doi.org/10.1016/j.ijhydene.2013.04.090 20 %X Among different Reactive Hydride Composites (RHCs), the combination of LiBH4 and MgH2 is a promising one for hydrogen storage, providing a high reversible storage capacity. During desorption of both LiBH4 and MgH2, the formation of MgB2 lowers the overall reaction enthalpy. In this work, the material was compacted to pellets for further improvement of the volumetric hydrogen capacity. The influence of compaction pressure on the apparent density, thermal conductivity and sorption behaviour for the Li-based RHC during cycling was investigated for the first time. Although LiBH4 melts during cycling, decrepitation or disaggregation of the pellets is not observed for any of the investigated compaction pressures. However, a strong influence of the compaction pressure on the apparent hydrogen storage capacity is detected. The influence on the reaction kinetics is rather low. To provide explanations for the observed correlations, SEM analysis before and after each sorption step was performed for different compaction pressures. Thus, the low hydrogen sorption in the first cycles and the continuously improving sorption for low pressure compacted pellets with cycling may be explained by some surface observations, along with the form stability of the pellets. %0 journal article %@ 0360-3199 %A Gosalawit-Utke, R.,Milanese, C.,Javadian, P.,Jepsen, J.,Laipple, D.,Karmi, F.,Puszkiel, J.,Jensen, T.R.,Marini, A.,Klassen, T.,Dornheim, M. %D 2013 %J International Journal of Hydrogen Energy %N 8 %P 3275-3282 %R doi:10.1016/j.ijhydene.2012.12.123 %T Nanoconfined 2LiBH4–MgH2–TiCl3 in carbon aerogel scaffold for reversible hydrogen storage %U https://doi.org/10.1016/j.ijhydene.2012.12.123 8 %X Nanoconfinement of 2LiBH4–MgH2–TiCl3 in resorcinol–formaldehyde carbon aerogel scaffold (RF–CAS) for reversible hydrogen storage applications is proposed. RF–CAS is encapsulated with approximately 1.6 wt. % TiCl3 by solution impregnation technique, and it is further nanoconfined with bulk 2LiBH4–MgH2 via melt infiltration. Faster dehydrogenation kinetics is obtained after TiCl3 impregnation, for example, nanoconfined 2LiBH4–MgH2–TiCl3 requires ∼1 and 4.5 h, respectively, to release 95% of the total hydrogen content during the 1st and 2nd cycles, while nanoconfined 2LiBH4–MgH2 (∼2.5 and 7 h, respectively) and bulk material (∼23 and 22 h, respectively) take considerably longer. Moreover, 95–98.6% of the theoretical H2 storage capacity (3.6–3.75 wt. % H2) is reproduced after four hydrogen release and uptake cycles of the nanoconfined 2LiBH4–MgH2–TiCl3. The reversibility of this hydrogen storage material is confirmed by the formation of LiBH4 and MgH2 after rehydrogenation using FTIR and SR-PXD techniques, respectively. %0 journal article %@ 1932-7447 %A Saldan, I.,Schulze, M.,Pistidda, C.,Gosalawit-Utke, R.,Zavorotynska, O.,Rude, L.H.,Skibsted, J.,Haase, D.,Cerenius, Y.,Jensen, T.R.,Spoto, G.,Baricco, M.,Taube, K.,Dornheim, M. %D 2013 %J The Journal of Physical Chemistry C %N 33 %P 17360-17366 %R doi:10.1021/jp405856s %T Hydrogen Sorption in the LiH–LiF–MgB2 System %U https://doi.org/10.1021/jp405856s 33 %X A composite material in the LiH–LiF–MgB2 system has been synthesized by high-energy ball milling. Some peaks in addition to that of the binary 2LiH–MgB2 and 2LiF–MgB2 systems are observed for the composite material by high-pressure differential scanning calorimetry (HP-DSC), indicating the formation of intermediate phases. In situ synchrotron radiation powder X-ray diffraction (SR-PXD) performed at 60 bar of H2 and 390 °C shows a superposition of both reaction pathways that are typical for 2LiH–MgB2 and 2LiF–MgB2. After hydrogen absorption of the LiH–LiF–MgB2 composite the vibrational modes of LiBH4 were observed by attenuated total reflection infrared (ATR-IR) spectroscopy. The 19F MAS NMR spectrum of the LiF–LiBH4 sample after heat treatment in hydrogen is strongly dominated by the centerband and spinning sidebands from LiF; in addition, a low-intensity resonance, very similar to that of [BF4] – ion, is identified. %0 journal article %@ 0360-3199 %A Gosalawit-Utke, R.,Milanese, C.,Nielsen, T.K.,Karimi, F.,Saldan, I.,Pranzas, K.,Jensen, T.R.,Marini, A.,Klassen, T.,Dornheim, M. %D 2013 %J International Journal of Hydrogen Energy %N 4 %P 1932-1942 %R doi:10.1016/j.ijhydene.2012.11.064 %T Nanoconfined 2LiBH4–MgH2 for reversible hydrogen storages: Reaction mechanisms, kinetics and thermodynamics %U https://doi.org/10.1016/j.ijhydene.2012.11.064 4 %X Samples of nanoconfined Reactive Hydride Composites in resorcinol–formaldehyde aerogel scaffolds (RF–CAS) are prepared by (i) direct melt infiltration of bulk 2LiBH4–MgH2; and (ii) MgH2 impregnation and LiBH4 melt infiltration. The reaction mechanisms, kinetics and thermodynamics of the systems are concluded. Activation energy (EA) and dehydrogenation enthalpies of LiBH4 and MgH2(ΔHdes,MgH2+ΔHdes,LiBH4) of nanoconfined 2LiBH4–MgH2 are in this work of interest. The hydrogen sorption reactions in both nanoconfined samples are reversible as shown by the recovering of LiBH4 and MgH2 after rehydrogenation. The titration results show the remarkable improvement in desorption kinetics of nanoconfined samples over the bulk material, such as more than 90% of overall hydrogen storage capacity is obtained within 2 h from the nanoconfined samples during the 1st dehydrogenation, while that of bulk material needs more than 16 h. The activation energy of the composites decreases by 27–170 kJ/mol (ΔEA) due to nanoconfinement. For thermodynamics, (ΔHdes,MgH2+ΔHdes,LiBH4) calculated from DSC results of the nanoconfined samples are in the range of 41–46 kJ/mol H2. %0 journal article %@ 0360-3199 %A Pistidda, C.,Napolitano, E.,Pottmaier, D.,Dornheim, M.,Klassen, T.,Baricco, M.,Enzo, S. %D 2013 %J International Journal of Hydrogen Energy %N 25 %P 10479-10484 %R doi:10.1016/j.ijhydene.2013.06.025 %T Structural study of a new B-rich phase obtained by partial hydrogenation of 2NaH + MgB2 %U https://doi.org/10.1016/j.ijhydene.2013.06.025 25 %X The structure of an unknown crystalline phase observed during the hydrogen absorption reaction of the powder mixtures 2NaH + MgB2 at high pressure has been studied by ab-initio structure determination from powder diffraction. The sequence of un-overlapped peaks extracted from the X-ray powder diffraction pattern could be indexed with a primitive cubic cell with lattice parameter a = 7.319 Å. The diffraction patterns of the peaks are matched with the Pa-3 space group. The stoichiometry of the hydrogen absorption reaction suggests the presence of a high-boron content phase in the compound under investigation. Assuming this phase to be composed only by boron atoms and therefore having a density similar to that found for boron polymorphs, the solution with a space group of Pa-3 leads to reasonable B–B interatomic distances. %0 journal article %@ 0960-1481 %A Nwakwuo, C.C.,Eigen, N.,Dornheim, M.,Bormann, R. %D 2012 %J Renewable Energy %N %P 172-178 %R doi:10.1016/j.renene.2011.11.036 %T Effect of group IV elements on the thermodynamic property of NaH + Al %U https://doi.org/10.1016/j.renene.2011.11.036 %X The destabilizing effect of (X) group IV elements (C, Si, Sn and Ge) on NaH + Al was investigated. A significant decrease in the desorption temperature as well as the reaction enthalpy of NaH was achieved with additions of C, Si, Ge and Sn due to the formation of NaAlGe and NaAlSi ternary and NaSn binary compounds. Compared to a reaction enthalpy of 114 kJ mol−1 H2 for NaH above 400 °C, lower reaction enthalpies of 94 kJ mol−1 H2, 72 kJ mol−1 H2, 20 kJ mol−1 H2 and 2 kJ mol−1 H2 were obtained for the NaH + Al + C, NaH + Al + Si, NaH + Al + Ge and NaH + Al + Sn mixtures with onsets at 270 °C, 220 °C, 180 °C, and 130 °C respectively. Reversible hydrogenation was partly achieved in the NaH–Al–Si system with the formation of NaAlH4 + Si. %0 journal article %@ 0360-3199 %A Saldan, I.,Campesi, R.,Zavorotynska, O.,Spoto, G.,Baricco, M.,Arendarska, A.,Taube, K.,Dornheim, M. %D 2012 %J International Journal of Hydrogen Energy %N 2 %P 1604-1612 %R doi:10.1016/j.ijhydene.2011.10.047 %T Enhanced hydrogen uptake/release in 2LiH–MgB2 composite with titanium additives %U https://doi.org/10.1016/j.ijhydene.2011.10.047 2 %X The influence of different titanium additives on hydrogen sorption in LiH–MgB2 system has been investigated. For all the composites LiH–MgB2–X (X = TiF4, TiO2, TiN, and TiC), prepared by ball-milling in molar ratios 2:1:0.1, five hydrogen uptake/release cycles were performed. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and attenuated total reflection infrared spectroscopy (ATR-IR) have been used to characterize crystal phases developed during the hydrogen absorption–desorption cycles.,All the composites with the titanium additives displayed an improvement of reaction kinetics, especially during hydrogen desorption. The LiH–MgB2–TiO2 system reached a storage of about 7.6 wt % H2 in ∼1.8 h for absorption and ∼2.7 h for desorption. Using in-situ SR-PXD measurements, magnesium was detected as an intermediate phase during hydrogen desorption for all composites. In the composite with TiF4 addition the formation of new phases (TiB2 and LiF) were observed. Characteristic diffraction peaks of TiO2, TiN and TiC additives were always present during hydrogen absorption–desorption. For all as-milled composites, ATR-IR spectra did not show any signals for borohydrides, while for all hydrogenated composites B–H stretching (2450–2150 cm−1) and B–H bending (1350–1000 cm−1) bands were exactly the same as for commercial LiBH4. %0 journal article %@ 0360-3199 %A Nwakwuo, C.C.,Pistidda, C.,Dornheim, M.,Hutchison, J.L.,Sykes, J.M. %D 2012 %J International Journal of Hydrogen Energy %N 3 %P 2382-2387 %R doi:10.1016/j.ijhydene.2011.10.070 %T Microstructural study of hydrogen desorption in 2NaBH4 + MgH2 reactive hydride composite %U https://doi.org/10.1016/j.ijhydene.2011.10.070 3 %X The desorption mechanism of as-milled 2NaBH4 + MgH2 was investigated by volumetric analysis, X-ray diffraction and electron microscopy. Hydrogen desorption was carried out in 0.1 bar hydrogen pressure from room temperature up to 450 °C at a heating rate of 3 °C min−1. Complete dehydrogenation was achieved in two steps releasing 7.84 wt.% hydrogen. Desorption reaction in this system is kinetically restricted and limited by the growth of MgB2 at the Mg/Na2B12H12 interface where the intermediate product phases form a barrier to diffusion. During desorption, MgB2 particles are observed to grow as plates around NaH particles. %0 journal article %@ 0360-3199 %A Bellosta von Colbe, J.M.,Metz, O.,Lozano, G.A.,Pranzas, K.P.,Schmitz, H.W.,Beckmann, F.,Schreyer, A.,Klassen, T.,Dornheim, M. %D 2012 %J International Journal of Hydrogen Energy %N 3 %P 2807-2811 %R doi:10.1016/j.ijhydene.2011.03.153 %T Behavior of scaled-up sodium alanate hydrogen storage tanks during sorption %U https://doi.org/10.1016/j.ijhydene.2011.03.153 3 %X Sodium alanate is being experimentally tested in scaled-up quantities. For this purpose, several tanks have been designed and constructed. The tank functionality during absorption and desorption of hydrogen was demonstrated in a scale of 8 kg of alanate, with a peak technical absorption time below 10 min. The absorption and desorption data show good reproducibility. Neutron radiography was used in another tank to show the powder’s physical behavior during sorption, showing conservation of the macroscopic structure during cycling. %0 journal article %@ 1932-7447 %A Gosalawit-Utke, R.,Nielsen, T.K.,Pranzas, K.,Saldan, I.,Pistidda, C.,Karimi, F.,Laipple, D.,Skibsted, J.,Jensen, T.R.,Klassen, T.,Dornheim, M. %D 2012 %J The Journal of Physical Chemistry C %N 1 %P 1526-1534 %R doi:10.1021/jp2088127 %T 2LiBH4MgH2 in a ResorcinolFurfural Carbon Aerogel Scaffold for Reversible Hydrogen Storage %U https://doi.org/10.1021/jp2088127 1 %X The reactive hydride composite of 2LiBH4–MgH2 has been melt infiltrated in a resorcinol–furfural (RFF) carbon aerogel scaffold. Dried aerogel of RFF, further pyrolyzed to obtain a carbon aerogel scaffold, is prepared by CO2 supercritical drying, where time consumption is significantly lower than the normal procedures of solvent exchange and drying under ambient conditions. On the basis of scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS) mapping, the complex hydrides are homogeneously dispersed in the nanometer scale both inside the nanopores and over the surface of the RFF carbon aerogel. Synchrotron radiation powder X-ray diffraction (SR–PXD) and Raman results reveal the reaction mechanisms during melt infiltration, de- and rehydrogenation of this system, as well as the differences from the previous studies of the nanoconfined 2LiBH4–MgH2 in a resorcinol–formaldehyde (RF) carbon aerogel. Thermogravimetric and hydrogen titration measurements reveal a significant improvement in dehydrogenation kinetics of 2LiBH4–MgH2–RFF as compared with the bulk 2LiBH4–MgH2 system. For instance, an approximate single-step dehydrogenation together with almost 100% of the total hydrogen storage capacity is accomplished within 6 h during the first dehydrogenation, while the bulk material performs clearly two-step reaction and requires 30 h (at T = 45 °C and p(H2) = 3–4 bar). Moreover, the gravimetric hydrogen storage capacity in the range of 4.2–4.8 wt % (10–11.2 wt % H2 with respect to the hydride content) is maintained over four dehydrogenation and rehydrogenation cycles. %0 journal article %@ 0360-3199 %A Jepsen, J.,Bellosta von Colbe, J.M.,Klassen, T.,Dornheim, M. %D 2012 %J International Journal of Hydrogen Energy %N 5 %P 4204-4214 %R doi:10.1016/j.ijhydene.2011.11.141 %T Economic potential of complex hydrides compared to conventional hydrogen storage systems %U https://doi.org/10.1016/j.ijhydene.2011.11.141 5 %X Novel developments of materials for solid hydrogen storage show promising prospects. Complex hydrides exhibit great technical potential to store hydrogen in an efficient and safe way. Nevertheless, so far an evaluation of economic competitiveness is still lacking. In this work, an assessment about the economic feasibility of implementing complex hydrides as hydrogen storage materials is presented. The cost structure of hydrogen storage systems based on NaAlH4 and LiBH4/MgH2 is discussed and compared with the conventional high pressure (700 bar) and liquid storage systems. The vessel construction for the complex hydride systems is much simpler than for the alternative conventional methods because of the milder pressure and temperature conditions during the storage process. According to the economical analysis, this represents the main cost advantage of the complex hydride systems. %0 journal article %@ 1932-7447 %A Suarez Alcantara, K.,Ramallo Lopez, J.M.,Boesenberg, U.,Saldan, I.,Pistidda, C.,Requejo, F.G.,Jensen, T.,Cerenius, Y.,Soerby, M.,Avila, J.,Bellosta von Colbe, J.,Taube, K.,Klassen, T.,Dornheim, M. %D 2012 %J The Journal of Physical Chemistry C %N 12 %P 7207-7212 %R doi:10.1021/jp211620h %T 3CaH2 + 4MgB2 + CaF2 Reactive Hydride Composite as a Potential Hydrogen Storage Material: Hydrogenation and Dehydrogenation Pathway %U https://doi.org/10.1021/jp211620h 12 %X A reactive hydride composite (RHC) with initial composition 3CaH2 + 4MgB2 + CaF2 was studied by in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and X-ray absorption near edge structure (XANES) at the B K-edge and at the Ca K-edge. The hydrogenation reaction proceeds by an unknown intermediate. No evidence of intermediates was observed during the dehydrogenation reaction. B and Ca K-edge XANES results hint to a closed interaction of CaF2 and Ca(BH4)2. The main function of CaF2 in the 3CaH2 + 4MgB2 + CaF2 RHC is as a dopant for the hydrogenation and dehydrogenation reactions. %0 journal article %@ 0360-3199 %A Lozano, G.A.,Na Ranong, C.,Bellosta von Colbe, J.M.,Bormann, R.,Hapke, J.,Fieg, G.,Klassen, T.,Dornheim, M. %D 2012 %J International Journal of Hydrogen Energy %N 3 %P 2825-2834 %R doi:10.1016/j.ijhydene.2011.03.043 %T Optimization of hydrogen storage tubular tanks based on light weight hydrides %U https://doi.org/10.1016/j.ijhydene.2011.03.043 3 %X Design of hydrogen storage systems aims at minimal weight and volume while fulfilling performance criteria. In this paper, the tubular tank configuration for hydrogen storage based on light weight hydrides is optimized towards its total weight using the predictions of a newly developed simulation model. Sodium alanate is taken as model material. A clear definition of the optimization is presented, stating a new optimization criterion: a defined total mass of hydrogen has to be charged in a given time, instead of prescribing percentages of the total hydrogen storage capacity. This yields a wider space of possible solutions. The effects of material compaction, addition of expanded graphite and different tubular tank diameters were evaluated. It was found that compaction of the material is the most influential factor to optimize the storage system. In order to obtain lighter storage systems one should concentrate on improving the ratio mass of hydride bed to mass of tank wall by screening lighter materials for the tank wall and developing hydrogen storage materials exhibiting both higher gravimetric and volumetric storage capacities. %0 journal article %@ 1932-7447 %A Saldan, I.,Gosalawit-Utke, R.,Pistidda, C.,Boesenberg, U.,Schulze, M.,Jensen, T.R.,Taube, K.,Dornheim, M.,Klassen, M. %D 2012 %J The Journal of Physical Chemistry C %N 12 %P 7010-7015 %R doi:10.1021/jp212322u %T Influence of Stoichiometry on the Hydrogen Sorption Behavior in the LiF–MgB2 System %U https://doi.org/10.1021/jp212322u 12 %X Chemical reactions between LiF and MgB2 with different molar ratios of 1:1 and 4:1 under hydrogen atmosphere were studied by high pressure differential scanning calorimetry (HP-DSC) and in-situ synchrotron radiation power X-ray diffraction (SR-PXD). Hydrogen sorption properties of the composites were evaluated using a Sievert’s type apparatus. After hydrogenation only LiBH4 and MgF2 are found as the main products. However, DSC characterization showed multistep events related to LiBH4 that might be explained by different phases or some intermediates. %0 journal article %@ 0378-7753 %A Lozano, G.A.,Bellosta von Colbe, J.M.,Bormann, R.,Klassen, T.,Dornheim, M. %D 2011 %J Journal of Power Sources %N 22 %P 9254-9259 %R doi:10.1016/j.jpowsour.2011.07.053 %T Enhanced volumetric hydrogen density in sodium alanate by compaction %U https://doi.org/10.1016/j.jpowsour.2011.07.053 22 %X Powder compaction is a potential process for the enhancement of the volumetric and gravimetric capacities of hydrogen storage systems based on metal hydrides. This paper presents the hydrogen absorption and desorption behaviour of compacts of sodium alanate material prepared under different levels of compaction pressure. It is shown that even at high compaction levels and low initial porosities, hydrogen absorption and desorption kinetics can proceed comparatively fast in compacted material. Furthermore, experimental hydrogen weight capacities of compacted material are higher than the experimental values obtained in case of loose powder. It is demonstrated that the kinetic behaviour of the compacted material during cycling is directly associated to the volumetric expansion of the compact, which is quantitatively measured and analyzed during both hydrogen absorption and desorption processes. The cycling behaviour and dimensional changes of compacted sodium alanate material are a key consideration point if it is used as hydrogen storage materials in practical tank systems. %0 journal article %@ 1932-7447 %A Gosalawit-Utke, R.,Suarez, K.,Bellosta von Colbe, J.M.,Boesenberg, U.,Jensen, T.R.,Cerenius, Y.,Bonatto Minella, C.,Pistidda, C.,Barkhordarian, G.,Schulze, M.,Klassen, T.,Bormann, R.,Dornheim, M. %D 2011 %J The Journal of Physical Chemistry C %N 9 %P 3762-3768 %R doi:10.1021/jp108236e %T Ca(BH4)2−MgF2 Reversible Hydrogen Storage: Reaction Mechanisms and Kinetic Properties %U https://doi.org/10.1021/jp108236e 9 %X A composite of Ca(BH4)2−MgF2 is proposed as a reversible hydrogen storage system. The dehydrogenation and rehydrogenation reaction mechanisms are investigated by in situ time-resolved synchrotron radiation powder X-ray diffraction (SR-PXD) and Raman spectroscopy. The formation of an intermediate phase (CaF2−xHx) is observed during rehydrogenation. The hydrogen content of 4.3 wt % is obtained within 4 h during the first dehydrogenation at isothermal and isobaric conditions of 330 °C and 0.5 bar H2, respectively. The cycling efficiency is evaluated by three release and uptake cycles together with absorbed hydrogen content in the range 5.1−5.8 wt % after 2.5 h (T = 330 °C and p(H2) = 130 bar). The kinetic properties on the basis of hydrogen absorption are comparable for all cycles. As compared to pure Ca(BH4)2 and Ca(BH4)2−MgH2 composite, Ca(BH4)2−MgF2 composite reveals the kinetic destabilization and the reproducibility of hydrogen storage capacities during cycling, respectively. %0 journal article %@ 1932-7447 %A Gosalawit-Utke, R.,Nielsen, T.K.,Saldan, I.,Laipple, D.,Cerenius, Y.,Jensen, T.R.,Klassen, T.,Dornheim, M. %D 2011 %J The Journal of Physical Chemistry C %N 21 %P 10903-10910 %R doi:10.1021/jp2021903 %T Nanoconfined 2LiBH4–MgH2 Prepared by Direct Melt Infiltration into Nanoporous Materials %U https://doi.org/10.1021/jp2021903 21 %X Nanoconfined 2LiBH4–MgH2 is prepared by direct melt infiltration of bulk 2LiBH4–MgH2 into an inert nanoporous resorcinol–formaldehyde carbon aerogel scaffold material. Scanning electron microscopy (SEM) micrographs and energy dispersive X-ray spectroscopy (EDS) mapping reveal homogeneous dispersion of Mg (from MgH2) and B (from LiBH4) inside the carbon aerogel scaffold. Moreover, nanoconfinement of LiBH4 in the carbon aerogel scaffold is confirmed by differential scanning calorimetry (DSC). The hydrogen desorption kinetics of the nanoconfined 2LiBH4–MgH2 is significantly improved as compared to bulk 2LiBH4–MgH2. For instance, the nanoconfined 2LiBH4–MgH2 releases 90% of the total hydrogen storage capacity within 90 min, whereas the bulk material releases only 34% (at T = 425 °C and p(H2) = 3.4 bar). A reversible gravimetric hydrogen storage capacity of 10.8 wt % H2, calculated with respect to the metal hydride content, is preserved over four hydrogen release and uptake cycles. %0 journal article %@ 1359-6462 %A Pistidda, C.,Barkhordarian, G.,Rzeszutek, A.,Garroni, S.,Bonatto Minella, C.,Baro, M.D.,Nolis, P.,Bormann, R.,Klassen, T.,Dornheim, M. %D 2011 %J Scripta Materialia %N 11 %P 1035-1038 %R doi:10.1016/j.scriptamat.2011.02.017 %T Activation of the reactive hydride composite 2NaBH4 + MgH2 %U https://doi.org/10.1016/j.scriptamat.2011.02.017 11 %X A novel method to enhance the reaction kinetics of the reactive hydride composite 2NaBH4 + MgH2 is described. It has been discovered that short-term exposure to a moist atmosphere has a very beneficial effect on the desorption reaction of the 2NaBH4 + MgH2 mixture. By this procedure it is possible to achieve, after drying, both faster desorption kinetics and greater amounts of released hydrogen compared to ball-milled material without further treatment. %0 journal article %@ 1359-6462 %A Nwakwuo, C.C.,Pistidda, C.,Dornheim, M.,Hutchison, J.L.,Sykes, J.M. %D 2011 %J Scripta Materialia %N 4 %P 351-354 %R doi:10.1016/j.scriptamat.2010.10.034 %T Microstructural analysis of hydrogen absorption in 2NaH + MgB2 %U https://doi.org/10.1016/j.scriptamat.2010.10.034 4 %X Transmission electron microscopy and in situ X-ray diffraction have been used to characterize the hydrogenation mechanism of ball-milled 2NaH + MgB2. Hydrogen absorption was performed under 50 bar hydrogen while heating from room temperature to 400 °C. A new and unknown hydride phase is observed at about 280 °C. This phase remains stable up to 320 °C and subsequently disappears, followed by the formation of perovskite-type NaMgH3 at about 330 °C. At 380 °C, crystals of NaBH4 appear and grow. %0 journal article %@ 1438-1656 %A Pranzas, K.P.,Boesenberg, U.,Karimi, F.,Muenning, M.,Metz, O.,Bonatto Minella, C.,Schmitz, H.-W.,Beckmann, F.,Vainio, U.,Zajak, D.,Welter, E.,Jensen, T.R.,Cerenius, Y.,Bormann, R.,Klassen, T.,Dornheim, M.,Schreyer, A. %D 2011 %J Advanced Engineering Materials %N 8 %P 730-736 %R doi:10.1002/adem.201000298 %T Characterization of Hydrogen Storage Materials and Systems with Photons and Neutrons %U https://doi.org/10.1002/adem.201000298 8 %X Complex hydrides are very promising candidates for future light-weight solid state hydrogen storage materials. The present work illustrates detailed characterization of such novel hydride materials on different size scales by the use of synchrotron radiation and neutrons. The comprehensive analysis of such data leads to a deep understanding of the ongoing processes and mechanisms. The reaction pathways during hydrogen desorption and absorption are identified by in situ X-ray diffraction (XRD). Function and size of additive phases are estimated using X-ray absorption spectroscopy (XAS) and anomalous small-angle X-ray scattering (ASAXS). The structure of the metal hydride matrix is characterized using (ultra) small-angle neutron scattering (SANS/USANS). The hydrogen distribution in tanks filled with metal hydride material is studied with neutron computerized tomography (NCT). The results obtained by the different analysis methods are summarized in a final structural model. The complementary information obtained by these different methods is essential for the understanding of the various sorption processes in light metal hydrides and hydrogen storage tanks. %0 journal article %@ 0360-3199 %A Pottmaier, D.,Pistidda, C.,Groppo, E.,Bordiga, S.,Spoto, G.,Dornheim, M.,Baricco, M. %D 2011 %J International Journal of Hydrogen Energy %N 13 %P 7891-7896 %R doi:10.1016/j.ijhydene.2011.01.059 %T Dehydrogenation reactions of 2NaBH4 + MgH2 system %U https://doi.org/10.1016/j.ijhydene.2011.01.059 13 %X Reactive Hydride Composites (RHCs), ball-milled composites of two or more different hydrides, are suggested as an alternative for solid state hydrogen storage. In this work, dehydrogenation of 2NaBH4 + MgH2 system under vacuum was investigated using complementary characterization techniques. At first, thermal programmed desorption of as-milled composite and single compounds was used to identify the temperature range of hydrogen release. RHC samples annealed at various temperatures up to 500 °C were characterized by X-ray diffraction, infrared spectroscopy and scanning electron microscopy. It was found that the dehydrogenation reaction under vacuum is likely to proceed as follows: 2NaBH4 + MgH2 (>250 °C) → 2NaBH4 + 1/2MgH2 + 1/2Mg + 1/2H2 (>350 °C) ↔ 3/2NaBH4 + 1/4MgB2 + 1/2NaH + 3/4Mg + 7/4H2 (>450 °C) → 2Na + B + 1/2Mg + 1/2MgB2 + 5H2. In addition, presence of NaMgH3 phase suggests the occurrence of secondary reactions. %0 journal article %@ 0021-8979 %A Deprez, E.,Munoz-Marquez, M.A.,Jimenez de Haro, M.C.,Palomares, F.J.,Soria, F.,Dornheim, M.,Bormann, R.,Fernandez, A. %D 2011 %J Journal of Applied Physics %N %P 014913 %R doi:10.1063/1.3525803 %T Combined x-ray photoelectron spectroscopy and scanning electron microscopy studies of the LiBH4–MgH2 reactive hydride composite with and without a Ti-based additive %U https://doi.org/10.1063/1.3525803 %X A detailed electronic and microstructural characterization is reported for the LiBH4–MgH2 reactive hydride composite system with and without titanium isopropoxide as additive. Surface characterization by x-ray photoelectron spectroscopy combined to a morphological study by scanning electron microscopy as well as elemental map composition analysis by energy dispersive x-ray emission are presented in this paper for the first time for all sorption steps. Although sorption reactions are not complete at the surface due to the unavoidable superficial oxidation, it has been shown that the presence of the additive is favoring the heterogeneous nucleation of the MgB2 phase. Ti-based phases appear in all the samples for the three sorption steps well dispersed and uniformly distributed in the material. Li-based phases are highly dispersed at the surface while the Mg-based ones appear, either partially covered by the Li-based phases, or forming bigger grains. Ball milling is promoting mixing of phases and a good dispersion of the additive what favors grain refinement and heterogeneous reactions at the interfaces. %0 journal article %@ 0022-4596 %A Suarez Alcantara, K.,Boesenberg, U.,Zavorotynska, O.,Bellosta von Colbe, J.,Taube, K.,Baricco, M.,Klassen, T.,Dornheim, M. %D 2011 %J Journal of Solid State Chemistry %N 11 %P 3104-3109 %R doi:10.1016/j.jssc.2011.09.019 %T Sorption and desorption properties of a CaH2/MgB2/CaF2 reactive hydride composite as potential hydrogen storage material %U https://doi.org/10.1016/j.jssc.2011.09.019 11 %X The hydrogenation behavior of 3CaH2+4MgB2+CaF2 composite was studied by manometric measurements, powder X-ray diffraction, differential scanning calorimetry and attenuated total reflection infrared spectroscopy. The maximum observed quantity of hydrogen loaded in the composite was 7.0 wt%. X-ray diffraction showed the formation of Ca(BH4)2 and MgH2 after hydrogenation. The activation energy for the dehydrogenation reaction was evaluated by DSC measurements and turns out to be 162±15 kJ mol−1 H2. This value decreases due to cycling to 116±5 kJ mol−1 H2 for the third dehydrogenation step. A decrease of ca. 25–50 °C in dehydrogenation temperature was observed with cycling. Due to its high capacity and reversibility, this composite is a promising candidate as a potential hydrogen storage material. %0 journal article %@ 1932-7447 %A Bonatto Minella, C.,Garroni, S.,Pistidda, C.,Gosalawit-Utke, R.,Barkhordarian, G.,Rongeat, C.,Lindemann, I.,Gutfleisch, O.,Jensen, T.R.,Cerenius, Y.,Christensen, J.,Baro, M.D.,Bormann, R.,Klassen, T.,Dornheim, M. %D 2011 %J The Journal of Physical Chemistry C %N 5 %P 2497-2504 %R doi:10.1021/jp107781m %T Effect of Transition Metal Fluorides on the Sorption Properties and Reversible Formation of Ca(BH4)2 %U https://doi.org/10.1021/jp107781m 5 %X Light metal borohydrides are considered as promising materials for solid state hydrogen storage. Because of the high hydrogen content of 11.5 wt % and the rather low dehydrogenation enthalpy of 32 kJ mol−1H2, Ca(BH4)2 is considered to be one of the most interesting compounds in this class of materials. In the present work, the effect of selected TM-fluoride (TM = transition metal) additives on the reversible formation of Ca(BH4)2 was investigated by means of thermovolumetric, calorimetric, Fourier transform infrared spectroscopy, and ex situ, and in situ synchrotron radiation powder X-ray diffraction (SR-PXD) measurements. Furthermore, selected desorbed samples were analyzed by 11B{1H} solid state magic angle spinning nuclear magnetic resonance (MAS NMR). Under the conditions used in this study (145 bar H2 pressure and 350 °C), TiF4 and NbF5 were the only additives causing partial reversibility. In these two cases, 11B{1H} MAS NMR analyses detected CaB6 and likely CaB12H12 in the dehydrogenation products. Elemental boron was found in the decomposition products of Ca(BH4)2 samples with VF4, TiF3, and VF3. The results indicate an important role of CaB6 for the reversible formation of Ca(BH4)2. %0 journal article %@ 1862-6300 %A Rude, L.H.,Nielsen, T.K.,Ravnsbaek, D.B.,Boesenberg, U.,Ley, M.B.,Richter, B.,Arnbjerg, L.M.,Dornheim, M.,Filinchuk, Y.,Besenbacher, F.,Jensen, T.R. %D 2011 %J Physica Status Solidi A %N 8 %P 1754-1773 %R doi:10.1002/pssa.201001214 %T Tailoring properties of borohydrides for hydrogen storage: A review %U https://doi.org/10.1002/pssa.201001214 8 %X Hydrogen is recognized as a possible future energy carrier, which can be produced from renewable energy and water. A major challenge in a future ‘hydrogen economy’ is the development of safe, compact, robust, and efficient means of hydrogen storage, in particular for mobile applications. The present review focuses on light metal boron based hydrides, for which the general interest has expanded significantly during the past few years. Synthesis methods, physical, chemical and structural properties of novel boron based hydrides are reviewed along with new approaches for improving kinetic and thermodynamic properties: (i) anion substitution, (ii) reactive hydride composites and (iii) nanoconfinement of hydrides and chemical reactions. The light metal borohydrides reveal a fascinating structural chemistry and have the potential for storing large amounts of hydrogen. A combination of the different approaches may provide a new route to a wide range of interesting energy storage materials in the future. %0 journal article %@ 1948-7185 %A Bonatto Minella, C.,Garroni, S.,Olid, D.,Teixidor, F.,Pistidda, C.,Lindemann, I.,Gutfleisch, O.,Baro, M.D.,Bormann, R.,Klassen, T.,Dornheim, M. %D 2011 %J The Journal of Physical Chemistry Letters %N 36 %P 18010-18014 %R doi:10.1021/jp204598a %T Experimental Evidence of Ca[B12H12] Formation During Decomposition of a Ca(BH4)2 + MgH2 Based Reactive Hydride Composite %U https://doi.org/10.1021/jp204598a 36 %X The combination of Ca(BH4)2 and MgH2 materials results in a composite with remarkable hydrogen storage properties. However, full reversibility upon the (re)hydrogenation reaction has not yet been achieved. The poor reversibility is shown to be linked to the formation of stable intermediate phases or side products upon decomposition. In this work, we show, for the first time, the clear experimental evidence of CaB12H12 among the decomposition products of a Ca(BH4)2 + MgH2 composite. A combination of 11B Magic Angle Spinning–Nuclear Magnetic Resonance (11B{1H} MAS NMR), ex situ X-ray diffraction (XRD) and Rietveld analysis are presented. An assessment of the (de)hydrogenation and (re)hydrogenation reactions of Ca(BH4)2 + MgH2 composite is reported. The experimental results provided in this work highlight the reasons for the limited reversibility observed in the Ca(BH4)2 + MgH2 composite upon (re)hydrogenation. %0 journal article %@ 0360-3199 %A Lozano, G.A.,Na Ranong, C.,Bellosta von Colbe, J.M.,Bormann, R.,Fieg, G.,Hapke, J.,Dornheim, M. %D 2010 %J International Journal of Hydrogen Energy %N 14 %P 7539-7546 %R doi:10.1016/j.ijhydene.2010.04.142 %T Empirical kinetic model of sodium alanate reacting system (II). Hydrogen desorption %U https://doi.org/10.1016/j.ijhydene.2010.04.142 14 %X Simulation and design of hydrogen storage systems based on metal hydrides require appropriate quantitative kinetic description. This paper presents an empirical kinetic model for the two-step hydrogen desorption of sodium alanate material doped with aluminium-reduced TiCl4, produced in kg-scale. The model is based on kinetic data obtained by volumetric titration measurements within a range of experimental conditions varying from 0 bar to 35 bar and from 100 °C to 190 °C. It is shown that while the first desorption step is a zero-order reaction, the second desorption step follows the Johnson–Mehl–Avrami (JMA) equation with n = 1. The predictions of the model are validated by experimental results and are used to asses the pressure–temperature (p–T) performance of the desorption steps against selected hydrogen supply criteria. This paper complements a previous paper of this investigation that presented the kinetic model of the corresponding hydrogen absorption of sodium alanate material. %0 journal article %@ 1359-6454 %A Boesenberg, U.,Kim, J.W.,Gosslar, D.,Eigen, N.,Jensen, T.R.,Bellosta von Colbe, J.M.,Zhou, Y.,Dahms, M.,Kim, D.H.,Guenther, R.,Cho, Y.W.,Oh, K.H.,Klassen, T.,Bormann, R.,Dornheim, M. %D 2010 %J Acta Materialia %N 9 %P 3381-3389 %R doi:10.1016/j.actamat.2010.02.012 %T Role of Additives in LiBH4-MgH2 Reactive Hydride Composite sorption reactions %U https://doi.org/10.1016/j.actamat.2010.02.012 9 %X The influence of additives on the reaction kinetics and microstructure refinement in LiBH4–MgH2 composites is investigated in detail. Indications of the rate-limiting processes during the reactions are obtained by comparison of the measured reaction kinetics with simulations with one specific rate-limiting process. The kinetics of the sorption reactions are derived from volumetric measurements as well as from in situ X-ray diffraction measurements. During desorption, the hydrogen is released at a constant rate, which is possibly correlated with the one-dimensional growth of MgB2 platelets. In contrast, the kinetic curves of the absorption reactions exhibit the typical shape of contracting-volume controlled kinetics. The microscopical interpretation of kinetic measurements are supported by transmission electron microscopy images confirming the formation of additive-nanostructures in the grain boundaries upon cycling. The present investigations underline the importance of the additives as nucleation substrates and the influence of microstructure on the reaction kinetics. %0 journal article %@ 1936-0851 %A Nielsen, T.K.,Boesenberg, U.,Gosalawit, R.,Dornheim, M.,Cerenius, Y.,Besenbacher, F.,Jensen, T.R. %D 2010 %J ACS Nano %N 7 %P 3903-3908 %R doi:10.1021/nn1006946 %T A Reversible Nanoconfined Chemical Reaction %U https://doi.org/10.1021/nn1006946 7 %X Hydrogen is recognized as a potential, extremely interesting energy carrier system, which can facilitate efficient utilization of unevenly distributed renewable energy. A major challenge in a future “hydrogen economy” is the development of a safe, compact, robust, and efficient means of hydrogen storage, in particular, for mobile applications. Here we report on a new concept for hydrogen storage using nanoconfined reversible chemical reactions. LiBH4 and MgH2 nanoparticles are embedded in a nanoporous carbon aerogel scaffold with pore size Dmax 21 nm and react during release of hydrogen and form MgB2. The hydrogen desorption kinetics is significantly improved compared to bulk conditions, and the nanoconfined system has a high degree of reversibility and stability and possibly also improved thermodynamic properties. This new scheme of nanoconfined chemistry may have a wide range of interesting applications in the future, for example, within the merging area of chemical storage of renewable energy. %0 journal article %@ 1359-6454 %A Deprez, E.,Justo, A.,Rojas, T.C.,Lopez-Cartes, C.,Bonatto Minella, C.,Boesenberg, U.,Dornheim, M.,Bormann. R.,Fernandez, A. %D 2010 %J Acta Materialia %N 17 %P 5683-5694 %R doi:10.1016/j.actamat.2010.06.043 %T Microstructural study of the LiBH4–MgH2 reactive hydride composite with and without Ti-isopropoxide additive %U https://doi.org/10.1016/j.actamat.2010.06.043 17 %X An exhaustive microstructural characterization is reported for the LiBH4–MgH2 reactive hydride composite (RHC) system with and without titanium isopropoxide additive. X-ray diffraction with Rietveld analysis, transmission electron microscopy coupled to energy dispersive X-ray analysis, selected-area electron diffraction and electron energy loss spectroscopy are presented in this paper for the first time for this system for all sorption steps. New data are reported regarding average crystallite and grain size, microstrain, phase formation and morphology; these results contribute to the understanding of the reaction mechanism and the influence of the additives on the kinetics. Microstructural effects, related to the high dispersion of titanium-based additives, result in a distinct grain refinement of MgB2 and an increase in the number of reaction sites, causing acceleration of desorption and absorption reactions. Considerations on the stability of phases under electron beam irradiation have also been reported. %0 journal article %@ 1932-7447 %A Boesenberg, U.,Ravnsbaek, D.B.,Hagemann, H.,D´Ánna, V.,Bonatto Minella, C.,Pistidda, C.,Beek, W.van,Jensen, T.R.,Bormann, R.,Dornheim, M. %D 2010 %J The Journal of Physical Chemistry C %N 35 %P 15212-15217 %R doi:10.1021/jp104814u %T Pressure and Temperature Influence on the Desorption Pathway of the LiBH4−MgH2 Composite System %U https://doi.org/10.1021/jp104814u 35 %X The decomposition pathway in LiBH4−MgH2 reactive hydride composites was investigated systematically as a function of pressure and temperature. Individual decomposition of MgH2 and LiBH4 is observed at higher temperatures and low pressures (T ≥ 450 °C and p(H2) ≤ 3 bar), whereas simultaneous desorption of H2 from LiBH4 and formation of MgB2 was observed at 400 °C and a hydrogen backpressure of p(H2) = 5 bar. The simultaneous desorption of H2 from LiBH4 and MgH2 without intermediate formation of metallic Mg could not be observed. In situ X-ray diffraction (XRD) and infrared (IR) spectroscopy reveal the present crystalline and amorphous phases. %0 journal article %@ 0360-3199 %A Lozano, G.A.,Na Ranong, C.,Bellosta von Colbe, J.M.,Bormann, R.,Fieg, G.,Hapke, J.,Dornheim, M. %D 2010 %J International Journal of Hydrogen Energy %N 13 %P 6763-6772 %R doi:10.1016/j.ijhydene.2010.04.080 %T Empirical kinetic model of sodium alanate reacting system (I). Hydrogen absorption %U https://doi.org/10.1016/j.ijhydene.2010.04.080 13 %X Hydrogen storage systems based on metal hydrides require appropriate quantitative kinetic description for simulations and designs, in particular for the crucial absorption process. This investigation proposes an empirical kinetic model for the hydrogen absorption of sodium alanate material doped with aluminium-reduced TiCl4, produced in kg-scale. The model is based on kinetic data obtained by volumetric titration measurements performed on each of the two absorption steps of sodium alanate, within a range of experimental conditions varying from 10 bar to 110 bar and from 100 °C to 180 °C. It is shown that each step is best described by the JMA model with n = 1.33. The kinetic equations are implemented in a mass balance and used to predict the reaction rate of the two steps of hydrogen absorption. Even when they proceed simultaneously, the predictions agree well with experimental results. The second paper of this investigation presents the results for the kinetic model of the corresponding hydrogen desorption. %0 journal article %@ 1932-7447 %A Pistidda, C.,Garroni, S.,Bonatto Minella, C.,Dolci, F.,Jensen, T.R.,Nolis, P.,Boesenberg, U.,Cerenius, Y.,Lohstroh, W.,Fichtner, M.,Baro, M.D.,Bormann, R.,Dornheim, M. %D 2010 %J The Journal of Physical Chemistry C %N 49 %P 21816-21823 %R doi:10.1021/jp107363q %T Pressure Effect on the 2NaH + MgB2 Hydrogen Absorption Reaction %U https://doi.org/10.1021/jp107363q 49 %X The hydrogen absorption mechanism of the 2NaH + MgB2 system has been investigated in detail. Depending on the applied hydrogen pressure, different intermediate phases are observed. In the case of absorption measurements performed under 50 bar of hydrogen pressure, NaBH4 is found not to be formed directly. Instead, first an unknown phase is formed, followed upon further heating by the formation of NaMgH3 and a NaH−NaBH4 molten salt mixture; only at the end after heating to 380 °C do the reflections of the crystalline NaBH4 appear. In contrast, measurements performed at lower hydrogen pressure (5 bar of H2), but under the same temperature conditions, demonstrate that the synthesis of NaBH4 is possible without occurrence of the unknown phase and of NaMgH3. This indicates that the reaction path can be tuned by the applied hydrogen pressure. The formation of a NaH−NaBH4 molten salt mixture is observed also for the measurement performed under 5 bar of hydrogen pressure with the formation of free Mg. However, under this pressure condition the formation of crystalline NaBH4 is observed only during cooling at 367 °C. For none of the applied experimental conditions has it been possible to achieve the theoretical gravimetric hydrogen capacity of 7.8 wt %. %0 journal article %@ 1932-7447 %A Gosalawit-Utke, R.,Bellosta von Colbe, J.M.,Dornheim, M.,Jensen, T.R.,Cerenius, Y.,Bonatto Minella, C.,Peschke, M.,Bormann, R. %D 2010 %J The Journal of Physical Chemistry C %N 22 %P 10291-10296 %R doi:10.1021/jp910266m %T LiF−MgB2 System for Reversible Hydrogen Storage %U https://doi.org/10.1021/jp910266m 22 %X LiF−MgB2 composites are proposed for reversible hydrogen storage. With respect to pure LiBH4, a significantly kinetic destabilization regarding hydrogenation and dehydrogenation is accomplished. The reversible hydrogen storage capacity is up to 6.4 wt %. The kinetic properties are improved significantly during cycling. The formations of the hydridofluoride phases (LiBH4−yFy and LiH1−xFx) are observed by in situ synchrotron X-ray diffraction (XRD) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Hydrogenation and dehydrogenation mechanisms are described on the basis of the formation and decomposition of the hydridofluoride phases, respectively. %0 journal article %@ 1932-7447 %A Deprez, E.,Munoz-Marquez, M.A.,Roldan, M.A.,Prestipino, C.,Palomares, F.J.,Bonatto Minella C.,Boesenberg, U.,Dornheim, M.,Bormann, R.,Fernandez, A. %D 2010 %J The Journal of Physical Chemistry C %N 7 %P 3309-3317 %R doi:10.1021/jp910955r %T Oxidation State and Local Structure of Ti-Based Additives in the Reactive Hydride Composite 2LiBH4 + MgH2 %U https://doi.org/10.1021/jp910955r 7 %X Nowadays, the technological utilization of reactive hydride composites (RHC) as hydrogen storage materials is limited by their reaction kinetics. However, addition of transition-metal-based additives, for instance titanium isopropoxide (Ti-iso), to the 2LiBH4+MgH2 system, results in a significant improvement of sorption kinetics. In this work, the evolution of chemical state and local structure of the Ti-based additive has been investigated by means of X-ray absorption (XAS) and photoemission (XPS) spectroscopy. X-ray absorption near-edge structure (XANES) as well as extended X-ray absorption fine structure (EXAFS) analysis have been undertaken at the Ti K-edge. The measurements reveal the formation of a highly dispersed and disordered TiO2-like phase during ball milling. During first desorption reduced titanium oxide and titanium boride are formed and remain stable upon cycling. The surface analysis performed by XPS shows that the reduction processes of the Ti-based additive during first desorption is coupled to the migration of the Ti species from the surface to the bulk of the material. Several factors, related to favoring heterogeneous nucleation of MgB2 and the increase of interfacial area through grain refinement are proposed as potential driving force, among other effects, for the observed kinetic improvement. %0 journal article %@ 0360-3199 %A Dolci, F.,Weidner, E.,Hoelzel, M.,Hansen, T.,Moretto, P.,Pistidda, C.,Brunelli, M.,Fichtner, M.,Lohstroh, W. %D 2010 %J International Journal of Hydrogen Energy %N 11 %P 5448-5453 %R doi:10.1016/j.ijhydene.2010.03.030 %T In-situ neutron diffraction study of magnesium amide/lithium hydride stoichiometric mixtures with lithium hydride excess %U https://doi.org/10.1016/j.ijhydene.2010.03.030 11 %X The hydrogen sorption of mixtures of magnesium amide (Mg(NH2)2) and lithium hydride (LiH) with different molecular ratios have been investigated using in-situ neutron diffraction; the experiments were performed at D20/ILL and SPODI/FRMII. The results reveal a common reaction pathway for 1:2, 3:8 and 1:4 magnesium amide: lithium hydride mixtures. Intermediate reaction steps are observed in both ab- and desorption. The thermodynamic properties of the system at 200 °C are not changed by the addition of excess lithium hydride. This finding has important implications for the tailoring the characteristics of this promising hydrogen storage material. %0 journal article %@ 0360-3199 %A Garroni, S.,Milanese, C.,Girella, A.,Marini, A.,Mulas, G.,Menendez, E.,Pistidda, C.,Dornheim, M.,Surinach, S.,Baro, M.D. %D 2010 %J International Journal of Hydrogen Energy %N 11 %P 5434-5441 %R doi:10.1016/j.ijhydene.2010.03.004 %T Sorption properties of NaBH4/MH2 (M = Mg, Ti) powder systems %U https://doi.org/10.1016/j.ijhydene.2010.03.004 11 %X The sorption properties of NaBH4/MH2 (M = Mg, Ti) powder systems prepared by high-energy ball milling have been thoroughly investigated. Concerning the systems containing MgH2, the 2:1 and 1:2 molar compositions have been studied and both lead to a multi-step desorption pathway, where the formation of MgB2 confirms the destabilization of NaBH4 induced by the presence of MgH2. A noticeable kinetic enhancement is achieved for the MgH2-rich system (composition 1:2) if compared with the NaBH4-rich system (composition 2:1). Even though full re-absorption is obtained for neither of the two compositions, fast kinetics is achieved. During absorption, the unsuspected formation of the perovskite-type hydride NaMgH3 is detected and it is showed that this ternary phase contributes to reduce the gravimetric capacity of the systems. Conversely, in the 2NaBH4/TiH2 system, there is no formation of the intermetallic compound TiB2. Furthermore, a decrease in the sorption kinetics is found in comparison with the systems based on MgH2. %0 journal article %@ 0925-8388 %A Pistidda, C.,Garroni, S.,Dolci, F.,Bardaji, E.,Khandelwal, A.,Nolis, P.,Dornheim, M.,Gosalawit, R.,Jensen, T.R.,Surinach, S.,Baro, M.D.,Lohstroh, W.,Fichtner, M. %D 2010 %J Journal of Alloys and Compounds %N 1 %P 212-215 %R doi:10.1016/j.jallcom.2010.07.226 %T Synthesis of amorphous Mg(BH4)2 from MgB2 and H2 at room temperature %U https://doi.org/10.1016/j.jallcom.2010.07.226 1 %X Due to its high hydrogen content and its favourable overall thermodynamics magnesium tetrahydroborate has been considered interesting for hydrogen storage applications. In this work we show that unsolvated amorphous magnesium tetrahydroborate can be obtained by reactive ball milling of commercial MgB2 under 100 bar hydrogen atmosphere. The material was characterized by solid-state NMR which showed the characteristic features of Mg(BH4)2, together with those of higher borohydride species. High pressure DSC and TPD-MS showed thermal behaviour similar to that of Mg(BH4)2 but with broadened signals. In situ synchrotron X-ray powder diffraction confirmed the amorphous state of the material and showed the typical crystalline decomposition products of Mg(BH4)2 at elevated temperatures. %0 journal article %@ 0360-3199 %A Sartori, S.,Qi, X.,Eigen, N.,Muller, J.,Klassen, T.,Dornheim, M.,Hauback, B.C. %D 2009 %J International Journal of Hydrogen Energy %N 10 %P 4582-4586 %R doi:10.1016/j.ijhydene.2008.10.087 %T A search for new Mg- and K-containing alanates for hydrogen storage %U https://doi.org/10.1016/j.ijhydene.2008.10.087 10 %X In this work Mg- and K-containing alanates have been investigated as possible hydrogen storage materials. Ball milling was carried out under argon or at moderate/high hydrogen pressure in order to obtain an improved driving force for the formation of potential new alanate phases. Powder X-ray diffraction and volumetric measurements were used in order to identify reaction mechanisms and phases forming in these systems. New unidentified peaks were detected for the mixtures 2MgH2 + 3Al + KH and 2CaH2 + Al + 2KH. However, they do not seem to belong to reversible hydride phases. %0 journal article %@ 0925-8388 %A Leon, A.,Zabara, O.,Sartori, S.,Eigen, N.,Dornheim, M.,Klassen, T.,Mueller, J.,Hauback, B.,Fichtner, M. %D 2009 %J Journal of Alloys and Compounds %N 1-2 %P 425-428 %R doi:10.1016/j.jallcom.2008.09.023 %T Investigation of (Mg, Al, Li, H)-based hydride and alanate mixtures produced by reactive ball milling %U https://doi.org/10.1016/j.jallcom.2008.09.023 1-2 %X Screening experiments were performed in order to investigate the formation of Al-based quaternary hydrides on the basis of multi-component mixtures treated by reactive ball milling under hydrogen pressure. The data indicated that the milling parameters and in particular the milling speed and milling time are of great importance to the formation of any new phase obtained by reactive ball milling. Indeed, a higher milling speed was shown to favour the formation of the new phases. In the case of (MgH2 + Al + LiH) and (MgH2 + LiAlH4) mixtures, the formation of a new phase was observed, which exhibits relatively fast decomposition kinetics. %0 journal article %@ 0360-3199 %A Lozano, G.A.,Eigen, N.,Keller, C.,Dornheim, M.,Bormann, R. %D 2009 %J International Journal of Hydrogen Energy %N 4 %P 1896-1903 %R doi:10.1016/j.ijhydene.2008.12.028 %T Effects of heat transfer on the sorption kinetics of complex hydride reacting systems %U https://doi.org/10.1016/j.ijhydene.2008.12.028 4 %X In this work, the effect of powder bed size on the absorption and desorption kinetics of NaAlH4 catalyzed with TiCl4 was studied experimentally. For this purpose, volumetric titration measurements were performed using cells of different diameters. The temperature was measured during the process at different positions inside the hydride bed, providing detailed information about the influence of heat conduction. Experimental results show that, under the applied conditions up to a critical size, larger diameters can lead to faster kinetics for the first and second absorption reactions. At larger cell diameters, however, temperatures up to 200 °C were measured during the first absorption step in the hydride bed. This leads to a significant delay in the start of the second absorption step, reducing the overall rate of the process. Reasons for the observed behaviour are discussed and measures for optimization are proposed. %0 journal article %@ 0957-4484 %A Boesenberg, U.,Vainio, U.,Pranzas, P.K.,Bellosta von Colbe, J.M.,Goerigk, G.,Welter, E.,Dornheim, M.,Schreyer, A.,Bormann, R. %D 2009 %J Nanotechnology %N 20 %P 204003 %R doi:10.1088/0957-4484/20/20/204003 %T On the chemical state and distribution of Zr- and V-based additives in reactive hydride composites %U https://doi.org/10.1088/0957-4484/20/20/204003 20 %X Reactive hydride composites (RHCs) are very promising hydrogen storage materials for future applications due to their reduced reaction enthalpies and high gravimetric capacities. At present, the materials' functionality is limited by the reaction kinetics. A significant positive influence can be observed with addition of transition-metal-based additives. To understand the effect of these additives, the chemical state and changes during the reaction as well as the microstructural distribution were investigated using x-ray absorption near-edge structure (XANES) spectroscopy and anomalous small-angle x-ray scattering (ASAXS). In this work, zirconium- and vanadium-based additives were added to 2LiBH4–MgH2 composites and 2LiH–MgB2 composites and measured in the vicinity of the corresponding absorption edge. The measurements reveal the formation of finely distributed zirconium diboride and vanadium-based nanoparticles. The potential mechanisms for the observed influence on the reaction kinetics are discussed. %0 journal article %@ 0930-7516 %A Na Ranong, C.,Hoehne, M.,Franzen, J.,Hapke, J.,Fieg, G.,Dornheim, M.,Eigen, M.,Bellosta von Colbe, J.,Metz, O. %D 2009 %J Chemical Engineering and Technology %N 8 %P 1154-1163 %R doi:10.1002/ceat.200900095 %T Concept, Design and Manufacture of a Prototype Hydrogen Storage Tank Based on Sodium Alanate %U https://doi.org/10.1002/ceat.200900095 8 %X In the framework of the EC project STORHY (Hydrogen Storage for Automotive Applications), the prototype of a solid storage tank for hydrogen based on sodium alanate was developed. A storage tank containing 8 kg sodium alanate was designed and manufactured with the objective of fast refueling. To obtain the optimum design of the storage tank a simulation tool was developed and validated by experiments with a laboratory-scale tubular reactor. Application of the simulation tool to different storage concepts and geometries yielded the final design. The chosen concept is modular, enabling simple scale-up. This is the basis for the future development of fuel cell vehicle storage tanks containing 5 kg of hydrogen. %0 journal article %@ 0925-8388 %A Eigen, N.,Boesenberg, U.,Bellosta von Colbe, J.,Jensen, T.,Cerenius, Y.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2009 %J Journal of Alloys and Compounds %N 1-2 %P 76-80 %R doi:10.1016/j.jallcom.2008.10.002 %T Reversible hydrogen storage in NaF–Al composites %U https://doi.org/10.1016/j.jallcom.2008.10.002 1-2 %X This work demonstrates that hydrogen can be reversibly stored in a composite of NaF and Al. NaF and Al reacts to a mixture of Na3AlF6 and NaAlH4 via hydridofluoride phases of the form Na3AlH6−xFx. The analysis of thermodynamics based on literature standard enthalpies of formation yields the technically favourable enthalpy of reaction of roughly 35 kJ/mol H2 for a theoretical gravimetric hydrogen storage capacity of 3.3 wt%. Reaction mechanisms are discussed with respect to substitution of hydrogen by fluorine in complex hydrides. %0 journal article %@ 0009-286X %A Na Ranong, C.,Hoehne, M.,Franzen, J.,Hapke, J.,Fieg, G.,Dornheim, M. %D 2009 %J Chemie - Ingenieur - Technik %N 5 %P 645-654 %R doi:10.1002/cite.200900008 %T Modellgestuetzte verfahrenstechnische Berechnung eines Metallhydridspeichers auf Natriumalanatbasis im Technikumsmassstab %U https://doi.org/10.1002/cite.200900008 5 %X Im Rahmen des EU-Projekts STORHY ist der Prototyp eines Metallhydridspeichers auf Natriumalanatbasis für automobile Anwendungen entwickelt worden. Besonderes Merkmal ist die Größe im Vergleich zu bisher vorhandenen Laborreaktoren. Mit Hilfe einer modell-gestützten Simulation wird sein Beladungsverhalten für verschiedene Betriebsbedingungen berechnet. Anhand der Ergebnisse werden die Wirksamkeit der Kühlung und ihr Optimierungspotenzial diskutiert. %0 journal article %@ 1359-6462 %A Garroni, S.,Pistidda, C.,Brunelli, M.,Vaughan, G.B.M.,Surinach, S.,Baro, M.D. %D 2009 %J Scripta Materialia %N 12 %P 1129-1132 %R doi:10.1016/j.scriptamat.2009.02.059 %T Hydrogen desorption mechanism of 2NaBH4 + MgH2 composite prepared by high-energy ball milling %U https://doi.org/10.1016/j.scriptamat.2009.02.059 12 %X The desorption mechanism of 2NaBH4 + MgH2 composite has been investigated. The results show that the chemical interaction between MgH2 and NaBH4 is capable of decreasing the dehydrogenation temperature with respect to the single compounds. The dehydriding reaction starts at around 320 °C with the desorption of the MgH2 to Mg and proceeds via the chemical dismutation of NaBH4 in NaH and an intermediate specie. In situ synchrotron X-ray powder diffraction indicates that MgB2 is one of the final reaction products. %0 journal article %@ 0925-8388 %A Eigen, N.,Gosch, F.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2008 %J Journal of Alloys and Compounds %N 1-2 %P 310-316 %R doi:10.1016/j.jallcom.2007.10.079 %T Improved hydrogen sorption of sodium alanate by optimized processing %U https://doi.org/10.1016/j.jallcom.2007.10.079 1-2 %X This work demonstrates that fast sorption kinetics in complex hydrides can be achieved by a simple synthesis method using cost-efficient initial components, if microstructure and powder morphology are optimized. NaH/Al precursors with TiCl4 catalyst were synthesised under varying conditions in argon atmosphere and cycled. The influence of powder morphology and microstructure resulting from different process conditions were studied in detail. It is shown that a homogeneous mixing of the phases and a high surface area of the material is essential for fast kinetics and high reversible capacity. The optimized process can be easily scaled up to a cost-efficient production process for large amounts of storage material and can also be applied for other complex hydrides. %0 journal article %@ 0025-5408 %A Ares, J.R.,Aguey-Zinsou, K.-F.,Porcu, M.,Sykes, J.M.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2008 %J Materials Research Bulletin %N 5 %P 1263-1275 %R doi:10.1016/j.materresbull.2007.05.018 %T Thermal and mechanically activated decomposition of LiAlH4 %U https://doi.org/10.1016/j.materresbull.2007.05.018 5 %X Thermal stability of as-received LiAlH4 and milled LiAlH4 has been investigated. The thermal decomposition mechanism of as-received LiAlH4 depends on the temperature–time history. Apparent activation energies and enthalpies of the reactions have been obtained. During milling treatment, the high temperature and pressures locally induced by shocks lead to LiAlH4 mechanically decomposition. The decomposition temperatures of LiAlH4 and Li3AlH6 are both reduced by not, vert, similar60 °C due to particle size reduction produced by mechanical milling. Besides, the activation energy of the decomposition reaction of LiAlH4 decreases as compared to as-received LiAlH4. Moreover, a layer of oxide (not, vert, similar5 nm) at the surface of the milled alanate Li3AlH6 is observed. This layer could have a drastic influence on decomposition H-kinetics. %0 journal article %@ 0169-4332 %A Borgschulte, A.,Bielmann, M.,Zuettel, A.,Barkhordarian, G.,Dornheim, M.,Bormann, R. %D 2008 %J Applied Surface Science %N 8 %P 2377-2384 %R doi:10.1016/j.apsusc.2007.09.069 %T Hydrogen dissociation on oxide covered MgH2 by catalytically active vacancies %U https://doi.org/10.1016/j.apsusc.2007.09.069 8 %X MgH2 is an important ingredient in modern reactive hydride composites to be used as hydrogen storage materials. The surface composition and chemical state of ball-milled MgH2 is studied during hydrogen desorption by means of X-ray photoelectron spectroscopy. Simultaneously, the desorption rate of hydrogen is monitored, which is compared to dissociative properties of the surface investigated by hydrogen–deuterium exchange experiments. It is found that MgH2 is also oxide covered during desorption demonstrating that MgO is able to recombine atomic hydrogen. The corresponding catalytic sites are associated with low coordinated surface vacancies on the oxide. The maximum surface concentration of these vacancies is very small, which is countered by a very high turnover frequency due to a small activation energy for dissociation of hydrogen of 0.1 eV on the single vacancy. The study provides insight into the catalytic role played by the oxide additives in MgH2, which are superior catalysts for hydrogen sorption even when compared to 3d-metals. %0 journal article %@ 1463-9076 %A Borgschulte, A.,Zuettel, A.,Hug, P.,Barkhordarian, G.,Eigen, N.,Dornheim, M.,Bormann, R.,Ramirez-Cuesta, A.J. %D 2008 %J Physical Chemistry Chemical Physics %N 27 %P 4045-4055 %R doi:10.1039/b803147a %T Hydrogen–deuterium exchange experiments to probe the decomposition reaction of sodium alanate %U https://doi.org/10.1039/b803147a 27 %X NaAlH4 is the archetypical complex hydride for hydrogen storage. The extraordinary effect of dopants on the sorption kinetics triggered the investigation of this empirical finding. In this paper, a short review of the state of the art is given. To gain further understanding of the mechanisms involved we label the interacting species during the sorption process. This was experimentally realized by hydrogen–deuterium exchange measurements during the decomposition of NaAlH4 followed by thermogravimetry, Raman spectroscopy and mass spectrometry. By these experiments we are able to obtain specific information on the diffusing species and formation of intermediates. The activation energy of tracer diffusion in NaAlH4 is found to be 0.28 eV. The results are evidence for a vacancy-mediated desorption process of NaAlH4. %0 journal article %@ 1932-7447 %A Barkhordarian, G.,Jensen, T.R.,Doppiu, S.,Boesenberg, U.,Borgschulte, A.,Gremaud, R.,Cerenius, Y.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2008 %J The Journal of Physical Chemistry C %N 7 %P 2743-2749 %R doi:10.1021/jp076325k %T Formation of Ca(BH4)2 from Hydrogenation of CaH2+MgB2 Composite %U https://doi.org/10.1021/jp076325k 7 %X The hydrogenation of the CaH2+MgB2 composite and the dehydrogenation of the resulting products are investigated in detail by in situ time-resolved synchrotron radiation powder X-ray diffraction, high-pressure differential scanning calorimetry, infrared, and thermovolumetric measurements. It is demonstrated that a Ca(BH4)2+MgH2 composite is formed by hydrogenating a CaH2+MgB2 composite, at 350 °C and 140 bar of hydrogen. Two phases of Ca(BH4)2 were characterized: α- and β-Ca(BH4)2. α-Ca(BH4)2 transforms to β-Ca(BH4)2 at about 130 °C. Under the conditions used in the present study, β-Ca(BH4)2 decomposes first to CaH2, Ca3Mg4H14, Mg, B (or MgB2 depending on experimental conditions), and hydrogen at 360 °C, before complete decomposition to CaH2, Mg, B (or MgB2), and hydrogen at 400 °C. During hydrogenation under 140 bar of hydrogen, β-Ca(BH4)2 is formed at 250 °C, and α-Ca(BH4)2 is formed when the sample is cooled to less than 130 °C. Ti isopropoxide improves the kinetics of the reactions, during both hydrogenation and dehydrogenation. The dehydrogenation temperature decreases to 250 °C, with 1 wt % of this additive, and hydrogenation starts already at 200 °C. We propose that the improved kinetics of the above reactions with MgB2 (compared to pure boron) can be explained by the different boron bonding within the crystal structure of MgB2 and pure boron. %0 journal article %@ 1932-7447 %A Corey, R.L.,Ivancic, T.M.,Shane, D.T.,Carl, E.A.,Bowman, R.C.,Bellosta von Colbe, J.M.,Dornheim, M.,Bormann, R.,Huot, J.,Zidan, R.,Stowe, A.C.,Conradi, M.S. %D 2008 %J The Journal of Physical Chemistry C %N 49 %P 19784-19790 %R doi:10.1021/jp807900r %T Hydrogen Motion in Magnesium Hydride by NMR %U https://doi.org/10.1021/jp807900r 49 %X In coarse-grained MgH2, the diffusive motion of hydrogen remains too slow (<105 hops s−1) to narrow the H NMR line up to 400 °C. Slow-motion dipolar relaxation time T1D measurements reveal the motion, with hopping rate ωH from 0.1 to 430 s−1over the range of 260 to 400 °C, the first direct measurement of H hopping in MgH2. The ωH data are described by an activation energy of 1.72 eV (166 kJ/mol) and attempt frequency of 2.5 × 1015 s−1. In ball-milled MgH2 with 0.5 mol % added Nb2O5 catalyst, line-narrowing is evident already at 50 °C. The line shape shows distinct broad and narrow components corresponding to immobile and mobile H, respectively. The fraction of mobile H grows continuously with temperature, reaching ∼30% at 400 °C. This demonstrates that this material’s superior reaction kinetics are due to an increased rate of H motion, in addition to the shorter diffusion paths from ball-milling. In ball-milled MgH2 without additives, the line-narrowed component is weaker and is due, at least in part, to trapped H2 gas. The spin−lattice relaxation rates T1−1 of all materials are compared, with ball-milling markedly increasing T1−1. The weak temperature dependence of T1−1 suggests a mechanism with paramagnetic relaxation centers arising from the mechanical milling. %0 journal article %@ 0925-8388 %A Mosegaard, L.,Moeller, B.,Joergensen, J.-E.,Boesenberg, U.,Dornheim, M.,Hanson, J.C.,Cerenius, Y.,Jakobsen, H.J.,Besenbacher, F.,Jensen, T.R. %D 2007 %J Journal of Alloys and Compounds %N %P 301-305 %R doi:10.1016/j.jallcom.2007.03.057 %T Intermediate phases observed during decomposition of LiBH4 %U https://doi.org/10.1016/j.jallcom.2007.03.057 %X Lithium tetrahydridoboranate is among the materials with the highest hydrogen content and has great potential as a possible H2-storage material, although, the release and uptake of H2 is not fully understood. In this work, LiBH4 was studied by in situ synchrotron radiation powder X-ray diffraction (PXD) and solid state CP/MAS NMR both at variable temperatures. This study revealed two new phases observed during dehydrogenation of LiBH4. Phase I is hexagonal, a = 4.93(2) and c = 13.47(3) Å and is observed in the temperature range not, vert, similar200–300 °C, and phase II is orthorhombic, a = 8.70(1), b = 5.44(1) and c = 4.441(8) Å and is observed in the temperature range not, vert, similar300–400 °C applying a constant heating rate of 5 °C/min. Apparently, I transforms into II, e.g. at a constant temperature of T = 265 °C after 5 h. Furthermore, a third phase, III, is observed in the temperature range RT to 70 °C, and is caused by a reaction between LiBH4 and water vapor from the atmosphere. Hydrogen release is associated with the decomposition of III at ca. 65 °C. %0 journal article %@ 0360-3199 %A Ares Fernandez, J.R.,Aguey-Zinsou, F.,Elsaesser, M.,Ma, X.Z.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2007 %J International Journal of Hydrogen Energy %N 8 %P 1033-1040 %R doi:10.1016/j.ijhydene.2006.07.011 %T Mechanical and thermal decomposition of LiAlH4 with metal halides %U https://doi.org/10.1016/j.ijhydene.2006.07.011 8 %X In the present paper, we investigate the thermal and mechanical decomposition of lithium alanate (LiAlH4) milled with different metal-halides (VCl3, VBr3 and AlCl3). We observed that the thermal decomposition temperature of LiAlH4 does not depend on the metal–halide and it is decreased by 25°C as compared to LiAlH4 without additives. Moreover, metal halides enhance the decomposition of LiAlH4 and Li3AlH6. The ability of the metal halides to decompose LiAlH4 and Li3AlH6 during milling follows the order: VCl3>VBr3>AlCl3. X-ray diffraction and IR spectroscopy did not allow detecting any change on the cell volume or on Al–H bond of the doped alanate suggesting that the additives seem to do not act as substitutes into the lattice of the alanate. %0 journal article %@ 0920-5861 %A Borgschulte, A.,Boesenberg, U.,Barkhordarian, G.,Dornheim, M.,Bormann, R. %D 2007 %J Catalysis Today %N 3-4 %P 262-269 %R doi:10.1016/j.cattod.2006.09.031 %T Enhanced hydrogen sorption kinetics of magnesium by destabilized MgH 2-delta %U https://doi.org/10.1016/j.cattod.2006.09.031 3-4 %X The kinetics of the reversible reaction of hydrogen gas with magnesium forming MgH2 is enhanced significantly by the addition of transition metals oxide catalysts and by using nanostructured powders. Hydrogen absorption and desorption properties of such systems were studied by,differential scanning calorimetry (DSC) under hydrogen atmosphere, from which the heat of hydride formation and decomposition is determined. Apart from Mg and stoichiometric MgH2, we find an additional, slightly destabilized phase, which is formed prior to MgH2 upon hydrogenation. The amount of this phase depends on the degree of nanostructuring and the used additive. X-ray diffraction measurements confirm the compared to MgH2 slightly different lattice parameters of the intermediate phase. The results correspond to recent neutron diffraction measurements, by which a,new MgH2d phase was found. We propose that this destabilized phase acts as a gateway for de-hydrogenation of MgH2. %0 journal article %@ 1359-6454 %A Boesenberg, U.,Doppiu, S.,Mosegaard, L.,Barkhordarian, G.,Eigen, N.,Borgschulte, A.,Jensen, T.R.,Cerenius, Y.,Gutfleisch, O.,Klassen, T.,Dornheim, M.,Bormann, R. %D 2007 %J Acta Materialia %N 11 %P 3951-3958 %R doi:10.1016/j.actamat.2007.03.010 %T Hydrogen sorption properties of MgH2-LiBH4 Composites %U https://doi.org/10.1016/j.actamat.2007.03.010 11 %X A detailed analysis of the reaction mechanism of the reactive hydride composite (RHC) MgH2 + 2LiBH4 ↔ MgB2 + 2LiH + 4H2 was performed using high-pressure differential scanning calorimetry (HP-DSC) measurements and in situ synchrotron powder X-ray diffraction (XRD) measurements along with kinetic investigations using a Sievert-type apparatus. For the desorption the following two-step reaction has been observed: MgH2 + 2LiBH4 ↔ Mg + 2LiBH4 + H2 ↔ MgB2 + 2LiH + 4H2. However, this reaction is kinetically restricted and proceeds only at elevated temperatures. In contrast to the desorption reaction, LiBH4 and MgH2 are found to form simultaneously under fairly moderate conditions of 50 bar hydrogen pressure in the temperature range of 250–300°C. As found in pure light metal hydrides, significant improvement of sorption kinetics is possible if suitable additives are used. %0 journal article %@ 0925-8388 %A Zander, D.,Lyubenova, L.,Koester, U.,Klassen, T.,Dornheim, M. %D 2007 %J Journal of Alloys and Compounds %N %P 753-755 %R doi:10.1016/j.jallcom.2006.08.151 %T Influence of the Nb2O5 distribution on the electrochemical hydrogenation of nanocrystalline magnesium %U https://doi.org/10.1016/j.jallcom.2006.08.151 %X Nanocrystalline Mg powder without and with 2 mol% Nb2O5 catalyst was studied as an electrode material for electrochemical hydrogen charging in a 6 M KOH electrolyte. A strong influence of the compaction parameters, the current density and the catalyst on the hydrogenation behavior was observed. The addition of graphite and PTFE to the Mg/Nb2O5 electrodes improves the charging kinetics as well as the hydrogen content. The hydrogen contents achieved in Mg with Nb2O5, however, show a broad scatter. It was concluded that the catalyst distribution influences the upper limit of the storage capacity as well as the oxidation process at the surface during preparation. Since the addition of Nb2O5 was observed to reduce the hydrogen overpotential of Mg depending on the catalyst distribution, it is assumed that the catalyst influences the electrode reactions. Therefore, hydrogenation was investigated for different Nb2O5 distributions at different current densities in detail. %0 journal article %@ 0021-8898 %A Pranzas, P.K.,Dornheim, M.,Boesenberg, U.,Ares Fernandez, J.R.,Goerigk, G.,Roth, S.V.,Gehrke, R.,Schreyer, A. %D 2007 %J Journal of Applied Crystallography %N S1 %P S 383-S 387 %R doi:10.1107/S0021889807008023 %T Small-angle scattering investigations of magnesium hydride used as a hydrogen storage material %U https://doi.org/10.1107/S0021889807008023 S1 %X In this work, high-energy ball-milled magnesium hydride samples used for,hydrogen storage are investigated using small- and ultra-small-angle neutron scattering (SANS) as well as small-angle X-ray scattering (SAXS). Size distributions of inhomogeneities with dimensions from 10 A ˚ up to more than 10 mm, corresponding to crystallite and particle sizes obtained by X-ray diffraction and electron microscopy, are determined as a function of milling time, milling tool material and added metal oxide catalysts in order to study the influence of the microstructure on the sorption kinetics. Significant changes of the volume fraction distributions are found for samples containing the catalyst chromium oxide, particularly when the catalyst particles are nanometre-sized.,Cr2O3 is an effective agent for breaking up particles during the milling process. The comparison of SANS and SAXS curves give some of the first information about the distribution of hydrogen-containing structures. Using anomalous small-angle X-ray scattering, an energy-dependent scattering is found for an,MgHx sample with 1 mol% Fe2O3. From the separated scattering curve a size distribution of hard spheres is obtained with a size range which is expected for crystallite and particle sizes of the Fe2O3 catalyst. Chemical shifts in the absorption spectra give information about the stability of the metal oxide catalysts during the milling process. %0 journal article %@ 0925-8388 %A Barkhordarian, G.,Klassen, T.,Dornheim, M.,Bormann, R. %D 2007 %J Journal of Alloys and Compounds %N 1-2 %P L18-L21 %R doi:10.1016/j.jallcom.2006.09.048 %T Unexpected kinetic effect of MgB2 in reactive hydride composites containing complex borohydrides %U https://doi.org/10.1016/j.jallcom.2006.09.048 1-2 %X Complex borohydrides of light metals are promising hydrogen storage materials due to their high hydrogen capacity. However, they exhibit two main drawbacks: their high thermodynamic stability and their slow kinetics. In the present work, the effect of various reactants on the formation kinetics of complex borohydrides is investigated. It is found that the kinetic barriers for the formation of LiBH4, NaBH4 and Ca(BH4)2 are drastically reduced when MgB2 is used instead of B as starting material. Since this kinetic enhancement is observed in all borohydride studied so far, the observed effect is attributed to the higher reactivity of B in MgB2 to form [BH4]− complexes. In addition, by using MgB2 instead of elemental B, the corresponding reaction enthalpies are reduced by about 10 kJ/mol H, while the high gravimetric hydrogen capacities are largely preserved, i.e. LiBH4 + MgH2 with 11.4 wt%, Ca(BH4)2 + MgH2 with 8.3 wt%, and NaBH4 + MgH2 with 7.8 wt%. %0 journal article %@ 1359-6462 %A Dornheim, M.,Doppiu, S.,Barhhordarian, G.,Boesenberg, U.,klassen, T.,Gutfleisch, O.,Bormann, R. %D 2007 %J Scripta Materialia %N 10 %P 841-846 %R doi:10.1016/j.scriptamat.2007.01.003 %T Hydrogen storage in magnesium-based hydrides and hydride composites %U https://doi.org/10.1016/j.scriptamat.2007.01.003 10 %X Mg and Mg-based hydrides have attracted much attention because of their high gravimetric hydrogen storage densities and favourable kinetic properties. Due to novel preparation methods and the development of suitable catalysts, hydrogen uptake and desorption is now possible within less than 2 min. However, the hydrogen reaction enthalpy of pure Mg is too high for many applications, for example, for the zero emission car. Therefore, different routes are explored to tailor the hydrogen reaction enthalpy to potential applications. This article summarizes the recent developments concerning sorption properties and thermodynamics of Mg-based hydrides for hydrogen storage applications. In particular, promising strategies to decrease the hydrogen reaction enthalpy by alloying and the use of reactive hydride composites are discussed. %0 journal article %@ 1359-6462 %A Eigen, N.,Keller, C.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2007 %J Scripta Materialia %N 10 %P 847-851 %R doi:10.1016/j.scriptamat.2007.01.024 %T Industrial production of light metal hydrides for hydrogen storage %U https://doi.org/10.1016/j.scriptamat.2007.01.024 10 %X Light metal hydrides show a high potential for reversible hydrogen storage applications. In view of the potential future storage of large amounts of hydrogen, an economic tonnage scale production will be required. This viewpoint set introduces production methods and discusses the potential for simplifying processing routes and reducing costs in view of an industrial mass production. For this purpose, sodium alanate, for which cost-competitive large-scale production is already considered feasible, is used as an example for future promising hydrides, like complex hydrides or reactive hydride composites. %0 journal article %@ 0921-4526 %A Pranzas, P.K.,Dornheim, M.,Bellmann, D.,Aguey-Zinsou, K.F.,Klassen, T.,Schreyer, A. %D 2006 %J Physica B %N 1 %P 630-632 %R doi:10.1016/j.physb.2006.06.119 %T SANS/USANS investigations of nanocrystalline MgH2 for reversible storage of hydrogen %U https://doi.org/10.1016/j.physb.2006.06.119 1 %X Nanocrystalline magnesium hydride is considered to be one of the most promising alternatives for the reversible storage of hydrogen. In this work structural changes of high-energy ball-milled MgHx and MgH2/Cr2O3 with varying hydrogen content were investigated with small and ultra small-angle neutron scattering (SANS/USANS) using different milling parameters, e.g., milling time, vial and ball material, to obtain information about hydrogen sorption and desorption mechanisms. In a first attempt size distributions of spheres with radii from 1 nm up to 20 μm were calculated in order to characterize the influence of cycling history on the microstructure. Apparent changes of crystallite and particle structures due to hydrogen loading and unloading were found. The use of Cr2O3 nanoparticle additives result in distinct differences of the obtained scattering curves, which indicate that Cr2O3 not only has a catalytic function for the hydrogen sorption properties of MgH2 but also serves as an agent to breakup particles during the milling process. The results demonstrate the potential of the combination of SANS and USANS for structural characterization of nanocrystalline light-metal hydrides over the large size range of 1 nm up to 20 μm. %0 journal article %@ 0925-8388 %A Zander, D.,Lyubenova, L.,Koester, U.,Dornheim, M.,Aguey-Zinsou, F.,Klassen, T. %D 2006 %J Journal of Alloys and Compounds %N 1-2 %P 298-301 %R doi:10.1016/j.jallcom.2005.06.063 %T The catalytic effect of Nb2O5 on the electrochemical hydrogenation of nanocrystalline magnesium %U https://doi.org/10.1016/j.jallcom.2005.06.063 1-2 %X Nanocrystalline Mg powder without and with 2 mol% Nb2O5 catalyst was studied in a 6M KOH electrolyte as electrode material for electrochemical hydrogen charging processes. Since the hydrogen overpotential of Mg, which is a measure of the hydrogen evolution at the electrode surface, was observed to be reduced by the addition of Nb2O5, it is assumed that the catalyst influences the electrode reactions.,Considering this assumption hydrogenation was studied at different current densities. The storage capacity as well as the kinetic of Mg/Nb2O5 electrodes increased significantly up to 1 wt.% H2 at a charging time of 30 min with decreasing current density. The storage capacity of nanocrystalline Mg powder showed only minor changes to lower hydrogen contents with decreasing current density. %0 journal article %@ 1438-1656 %A Dornheim, M.,Eigen, N.,Barkhordarian, G.,Klassen, T.,Bormann, R. %D 2006 %J Advanced Engineering Materials %N 5 %P 377-385 %R doi:10.1002/adem.200600018 %T Tailoring Hydrogen Storage Materials Towards Application %U https://doi.org/10.1002/adem.200600018 5 %X A breakthrough in hydrogen storage technology was achieved by preparing nanocrystalline hydrides,using high-energy ball milling and the use of suitable catalysts/additives. These new materials show fast or in case of Mg-based hydrides very fast absorption and desorption kinetics within minutes, thus qualifying lightweight Mg- or Al-based hydrides for storage applications. This article summarizes our current understanding of the kinetics of Mg-based light metal hydrides, describes an approach for a cost-effective processing technology and highlights some promising new developments in lightweight metal hydride research. %0 journal article %@ 0169-4332 %A Friedrichs, O.,Sanchez-Lopez, J.C.,Lopez-Cartes, C.,Dornheim, m.,Klassen, T.,Bormann, R.,Fernandez, A. %D 2006 %J Applied Surface Science %N %P 2334-2345 %R doi:10.1016/j.apsusc.2005.04.018 %T Chemical and microstructural study of the oxygen passivation behaviour of nanocrystalline Mg and MgH2 %U https://doi.org/10.1016/j.apsusc.2005.04.018 %X Nanocrystalline Mg and MgH2 samples have been prepared by high-energy ball milling and gas phase condensation methods. Starting from these materials in their ‘‘as received’’ state without air exposure, a study of the oxygen and air passivation behaviour was carried out by ‘‘in situ’’ analysis of the samples by X-ray photoelectron spectroscopy (XPS) and transmission,electron microscopy (TEM). The binding energy and photoemission Auger parameters have been determined for metallic magnesium as well as for magnesium hydride, oxide and hydroxide species. Values of the MgH2 material were reported for the first time. The study clearly shows the formation of an oxide passivation layer of ca. 3–4 nm in thickness for all the nanocrystalline magnesium samples handled under controlled inert gas atmospheres. A hydroxide like amorphous layer is,formed at the topmost surface layers of the nanocrystalline Mg and MgH2 samples. The implication of these studies for H2 storage and transport applications of nanocrystalline magnesium is discussed. %0 journal article %@ 0925-8388 %A Huhn, P.-A.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2005 %J Journal of Alloys and Compounds %N %P 499-502 %R doi:10.1016/j.jallcom.2004.10.087 %T Thermal Stability of Nanocrystalline Magnesium for Hydrogen Storage %U https://doi.org/10.1016/j.jallcom.2004.10.087 %X Magnesium hydride is considered to be one of the most interesting alternatives for the reversible storage of hydrogen. It is abundant, inexpensive, easy to handle, environmentally benign and exhibits a high hydrogen storage capacity of up to 7.6 wt.%. Furthermore, nanocrystalline Mg powder prepared by high energy ball milling and the addition of suitable catalysts shows very fast absorption and desorption kinetics. The thermal stability of the nanocrystalline microstructure as well as the respective sorption kinetics of ball-milled MgH2 with or without 0.5 mol% Nb2O5 as catalyst have been investigated after cycling and annealing at the technically relevant temperatures between 300 and 400 ◦C. While kinetics for pure MgH2 slows down substantially already after a few cycles at 300 ◦C, MgH2 with Nb2O5 catalyst still shows fast sorption kinetics after annealing up to 370 ◦C. At higher temperatures, the kinetics for the catalyzed material also breaks down, which is attributed to a deterioration of the catalyst. Continuous coarsening of the microstructure during annealing leads to an increased fraction of the storage capacity that can only be recharged at a slower rate. This is discussed in terms of retarded growth conditions for the MgH2 phase. %0 journal article %@ 0925-8388 %A Deledda, S.,Borissova, A.,Poisignon, C.,Botta, W.J.,Yavari, A.R.,Dornheim, M.,Klassen, T. %D 2005 %J Journal of Alloys and Compounds %N %P 409-412 %R doi:10.1016/j.jallcom.2005.01.115 %T H-Sorption in MgH2 Nanocomposites Containing Fe or Ni with Fluorine %U https://doi.org/10.1016/j.jallcom.2005.01.115 %X Ball milling techniques were used to introduce both fluorine and catalytic transition metals (Fe, Ni) into MgH2 nanograined powders. XRD was carried out to follow the structural evolution upon milling, whereas the thermal stability against H-desorption was investigated by DSC,and TG analysis. The latter showed that fluorine additions with the Fe catalyst effectively decrease the desorption temperature to about 500 K. Results on the absorption/desorption kinetics, which was investigated by volumetric techniques, are presented and discussed with respect to both the simultaneous catalytic activity of Fe or Ni with F and the effect of solid-state processes which may occur upon mechanical alloying. %0 journal article %@ 0925-8388 %A Doppiu, S.,Solsona, P.,Spassov, T.,Barkhordarian, G.,Dornheim, M.,Klassen, T.,Surinach, S.,Baro, M.D. %D 2005 %J Journal of Alloys and Compounds %N %P 27-30 %R doi:10.1016/j.jallcom.2005.02.082 %T Thermodynamic properties and absorption-desorption kinetics of Mg87Ni10Al3 alloy synthesised by reactive ball milling under H2 atmosphere %U https://doi.org/10.1016/j.jallcom.2005.02.082 %X In this work, the synthesis of Mg87Ni10Al3 hydride by reactive ball milling under H2 atmosphere is presented. Reactive milling under,hydrogen induces the conversion of Mg into nanocrystalline MgH2 (final crystallite sizes ∼8 nm). The percentage of the hydride increases,with the milling time and after 20 h of mechanical treatment the reaction is complete. Only at longer milling time, when a high conversion,degree of Mg into the hydride is reached, the reaction with Ni to form Mg2NiH4 is observed. Thermal analysis shows that, for the shorter,milling time, the decomposition of the hydride starts at ∼200 ◦C, but the stability of the hydride slightly increases with increasing milling,time. Fast absorption–desorption kinetics is obtained at 300 ◦C. %0 journal article %@ 0925-8388 %A Ma, X.,Martinez-Franco, E.,Dornheim, M.,Klassen, T.,Bormann, R. %D 2005 %J Journal of Alloys and Compounds %N %P 771-774 %R doi:10.1016/j.jallcom.2004.10.100 %T Catalyzed Na2LiAlH6 for hydrogen storage %U https://doi.org/10.1016/j.jallcom.2004.10.100 %X In the present study, the complex alanate Na2LiAlH6 is synthesized by high-energy milling of powder blends containing NaH and LiAlH4.,The related thermodynamics are determined. In addition, a comprehensive study was performed to investigate the influence of different oxide and halide catalysts on the kinetics of hydrogen absorption and desorption, as well as their general drawback to decrease storage capacity.