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 NaAlH4 decomposition products.