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.% LaH_3.01 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% CeH_2.51 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 LaH_3.01 and CeH_2.51 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.