Catalyzed rehydrogenation of NaAlH₄: Ti and friends are active on NaH surfaces; Pt and friends are not

Density functional theory calculations have been performed on slabs of NaH doped with transition metals. These calculations suggest barrierless dissociative chemisorption of H₂ onto Sc, Ti, and V dopant sites, while indicating that Rh and Pt do not support dissociative chemisorption. Furthermore, sufficient energy is liberated in the H₂ adsorption to allow at least one of the adsorbed hydrogen atoms to diffuse away from the adsorption site without additional energy input. Detaching the second adsorbed hydrogen atom requires a small energy input. These results support an active hydrogen pump mechanism being involved in the rehydrogenation of NaAlH ₄ decomposition products.