AlH3-mediated mechanism in hydriding/dehydriding of NaAlH4

By theoretical investigation, we found that the balanced Fermi level in NaAlH4 is pinned by the vacancy pair of its ionic components ( V Na − and V AlH 4 + ), which significantly affects the formation enthalpies of other possible charged defects. V Na − and V AlH 4 + easily form V Na–AlH 4 0 vacancy complex on surface but not in bulk. This helps the diffusion of V Na − and V AlH 4 + , but will not induce the decomposition of NaAlH4 directly. In fact, we found that V AlH 3 0 plays a critical role in the decomposition of NaAlH4 and an AlH3-mediated mechanism for the hydriding/dehydriding of NaAlH4 is suggested.