Catalytic effect of Ti on dehydrogenation of Na3AlH6: A first principles investigation

In the present work, ab initio calculations were performed for the Ti-doped Na3AlH6 to investigate influence of dopant Ti on the hydrogenation/dehydrogenation properties of Na3AlH6. Substitution of Ti for Al and Na atoms, respectively, and an interstitial occupation of Ti in this compound were studied. It was found that Ti prefers to substitute for Al atom with the lowest occupation energy of 0.64 eV among the considered systems. The influence of Ti on hydrogenation/dehydrogenation properties of Na3AlH6 was sensitive to its occupation behavior. Ti greatly decreases the dehydrogenation energy of Na3AlH6 if it substituted for a Na atom. A mechanism described the Ti catalytic reversible reaction of NaAlH4 → Na3AlH6 was proposed based on the electronic analysis in this paper.