Influence of lanthanon hydride catalysts on hydrogen storage properties of sodium alanates

NaAlH4 complex hydrides doped with lanthanon hydrides were prepared by hydrogenation of the ball-milled NaH/Al+ xmol.% RE-H composites (RE=La, Ce; x=2, 4, 6) using NaH and Al powder as raw materials. The influence of lanthanon hydride catalysts on the hydriding and dehydriding behaviors of the as-synthesized composites were investigated. It was found that the composite doped with 2 mol.% LaH3.01 displayed the highest hydrogen absorption capacity of 4.78 wt.% and desorption capacity of 4.66 wt.%, respectively. Moreover, the composite doped with 6 mol% CeH2.51 showed the best hydriding/dehydriding reaction kinetics. The proposed catalytic mechanism for reversible hydrogen storage properties of the composite was attributed to the presence of active LaH3.01 and CeH2.51 particles, which were scattering on the surface of NaH and Al particles, acting as the catalytic active sites for hydrogen diffusion and playing an important catalytic role in the improved hydriding/dehydriding reaction.