Synergistic effect of Li–Ti and K–Ti co-doping on the dehydrogenation properties of NaAlH4: an ab initio study

Abstract

The synergistic effect of Li–Ti and K–Ti dopants on the energy, structure and electronic properties of NaAlH₄ has been investigated using density functional theory and ab initio molecular dynamics. Pair distribution functional analyses show that the substitution of NaAlH₄ by Li₂Ti and K₂Ti favor not only the release of H₂ but also the reductions in the barrier energies of (AlH₄)⁻ units. Density of states analyses suggest that the weakening of Al–H bonds in Li₂Ti- and K₂Ti-doped NaAlH₄ is attributed to the formation of Ti–Al and Ti–H phases. Bader atomic charges analyses imply that the strong interaction of Li–Al prevent the further formation of Ti–Al clusters. The results of H removal energies analyses reveal that both Li₂Ti and K₂Ti are favorable catalysts for NaAlH₄. Thus, that a Li₂Ti dopant, with lighter weight than K₂Ti, can be applied as a favorable catalyst for NaAlH₄ has been given for the first time.