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MgH 2 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 MgH 2 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 MgH 2 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 MgH 2 , which are superior catalysts for hydrogen sorption even when compared to 3d-metals.

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.

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.

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. Fil: Gosalawit Utke, Rapee. Helmholtz-Zentrum Geesthacht; Alemania. Suranaree University of Technology; Tailandia Fil: Milanese, Chiara. Università degli studi di Pavia; Italia Fil: Javadian, Payam. University Aarhus; Dinamarca Fil: Jepsen, Julian. Helmholtz-Zentrum Geesthacht; Alemania Fil: Laipple, Daniel. Helmholtz-Zentrum Geesthacht; Alemania Fil: Karmi, Fahim. Helmholtz-Zentrum Geesthacht; Alemania Fil: Puszkiel, Julián Atilio. Helmholtz-Zentrum Geesthacht; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Jensen, Torben R.. University Aarhus; Dinamarca Fil: Marini, Amedeo. Università degli studi di Pavia; Italia Fil: Klassen, Thomas. Helmholtz-Zentrum Geesthacht; Alemania Fil: Dornheim, Martin. Helmholtz-Zentrum Geesthacht; Alemania

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 NaAlH 4 and LiBH 4 /MgH 2 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.

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.

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. European Commission MRTN-CT-2006-035366 Ministerio de Ciencia e Innovación CTQ2009-13440