Alanates, a Comprehensive Review

Hydrogen storage is widely recognized as one of the biggest not solved problem within hydrogen technologies. The slow development of the materials and systems for hydrogen storage has resulted in a slow spread of hydrogen applications. There are many families of materials that can store hydrogen; among them, the alanate family can be of interest. Basic research papers and reviews have been focused on alanates of group 1 and 2. However, there are many alanates of transition metals, main group, and lanthanides that deserve attention in a review. This work is a comprehensive compilation of all known alanates. The approaches towards tuning the kinetics and thermodynamics of alanates are also covered in this review. These approaches are the formation of reactive composites, double cation alanates, or anion substitution. The crystallographic and X-ray diffraction characteristics of each alanate are presented along with this review. In the final sections, a discussion of the infrared, Raman, and thermodynamics was included.

Enhancing hydrogen storage performances of MgH2 by Ni nano-particles over mesoporous carbon CMK-3

Nano-dispersed Ni particles over mesoporous carbon material CMK-3 (Ni/CMK-3) was fabricated by means of impregnation-reduction strategy using precursor NiCl₂ · 6H₂O, which is beneficial to improving the de/rehydrogenation performances of MgH₂. The dehydrogenation onset temperature of MgH₂-Ni/CMK-3 is significantly lowered by 170 K from that of pristine MgH₂ (around 603 K). Totally 5.9 wt% of hydrogen absorption capacity is liberated within 1 h at a temperature of 423 K under a pressure of 3 MPa. This composite can absorb 3.9 wt% hydrogen even at a temperature of 328 K under 3 MPa H₂. Activation energy values of both dehydrogenation (43.4 kJ mol^-1) and rehydrogenation (37.4 kJ mol^-1) for MgH₂-Ni/CMK-3 are greatly enhanced from those of as-milled MgH₂. Ni/CMK-3 also slightly destabilizes the dehydrogenation of MgH₂ by 1.5 kJ mol [Formula: see text] The enhanced performances can be attributed to the synergistic effects of both destabilization and activation from nano-dispersed Ni particles.

Enhanced H2 sorption performance of magnesium hydride with hard-carbon-sphere-wrapped nickel

Magnesium hydride is regarded as one of the most ideal candidates for hydrogen storage, but its relatively high operating temperatures and slow kinetics always hinder its commercial applications. Herein, we first fabricated hard-carbon-sphere-wrapped Ni (Ni/HCS) via a mild chemical method; subsequently, the as-prepared additive was introduced to fabricate an Mg–Ni/HCS composite by using hydriding combustion synthesis. Hard carbon spheres (HCS) effectively inhibited the agglomeration of hydride particles during hydrogen storage cycling; they could also provide active sites to promote the nucleation of Mg-based hydrides. During the hydriding combustion synthesis procedure, in situ-formed Mg₂NiH₄ could induce the absorption of MgH₂, thus triggering its hydrogen properties. Remarkable enhancement in hydrogen absorption properties of the composite was found. The composite absorbed 6.0 wt% H₂ within 5 min at 275 °C; moreover, even at 75 °C, it could still absorb 3.5 wt% H₂. Furthermore, it delivered a high reversible hydrogen absorption capacity of 6.2 wt% and excellent rate capability at 350 °C. It was also demonstrated that the composite could release 6.2 wt% H₂ at 350 °C within 5 min. A rather low activation energy value (65.9 kJ mol⁻¹) for the dehydrogenation of MgH₂ was calculated as compared to that for commercial MgH₂ (133.5 kJ mol⁻¹).

Magnesium hydride is regarded as one of the most ideal candidates for hydrogen storage, but its relatively high operating temperatures and slow kinetics always hinder its commercial applications.

Constant rate thermal analysis of a dehydrogenation reaction

The kinetic analysis of constant rate thermal analysis (CRTA) curves obtained for MgH₂ dehydrogenation under high vacuum reveals that the reaction obeys first-order kinetics.

Enhanced hydrogen storage properties of MgH2 co-catalyzed with K2NiF6 and CNTs

The active species KF, KH and Mg₂Ni together with the unique structure of the CNTs functioned as a real catalyst.

Crystal feature and electronic structure of novel mixed alanate LiCa(AlH4)3: a density functional theory investigation

The H coordinates are predicted for LiCa(AlH₄)₃ in which Li–H bonding and Ca–H anti-bonding interactions are illustrated.

Synergistically thermodynamic and kinetic tailoring of the hydrogen desorption properties of MgH2 by co-addition of AlH3 and CeF3

The hydrogen desorption properties of MgH₂ are thermodynamically and kinetically improved by the synergistic addition of AlH₃ and CeF₃.

A study on the effects of K2ZrF6 as an additive on the microstructure and hydrogen storage properties of MgH2

It was found that the MgH₂ + 10 wt% K₂ZrF₆ sample started to decompose at around 250 °C, which was 100 °C and lower than in as-milled MgH₂. The re/dehydrogenation kinetics had also improved significantly compared to the undoped MgH₂.

Improved hydrogen storage properties of MgH2 by addition of Co2NiO nanoparticles

The result showed that the addition of 10 wt% Co₂NiO to the MgH₂ exhibits a lower onset desorption temperature. The dehydrogenation and rehydrogenation kinetics of MgH₂ + 10 wt% Co₂NiO were also improved compared to un-doped MgH₂.

Enhanced hydrogen storage properties of LiAlH4 catalyzed by CoFe2O4 nanoparticles

The catalytic effects of CoFe₂O₄ nanoparticles on the hydrogen storage properties of LiAlH₄ prepared by ball milling were investigated.