Role of Fe, Co and Ni in dehydrogenation thermodynamics and kinetics of LiBH4 (010) surface: a first-principles study

The present work gives the occupation energy, hydrogen diffusion/dissociation barrier, hydrogen dissociation energy and electronic structures of LiBH4 (010) surface with Fe, Co and Ni additives, using first-principles density functional theory calculations. It shows that on LiBH4 (010) surface, Fe, Co and Ni all energetically prefers to occupy the interstitial sites vs. Li/B sites, independent of their concentration. Fe, Co and Ni adding enable the hydrogen diffusion/dissociation barrier and hydrogen dissociation energy to dramatically reduce in the sequence of clean surface > Fe-doped surface > Co-doped surface > Ni-doped surface (contrary to the trend of cation electronegativity Li < Li-Fe < Li-Co < Li-Ni). This allows an efficient modification on dehydrogenation thermodynamics and kinetics of LiBH4 (010) surface, and is ascribed to the destabilization of Li/B-H bond and the formation of Fe/Co/Ni-B bond. Our work theoretically confirms a positive role of high electronegative metal on H-desorption of LiBH4, and is useful for designing advanced metal hydrides for hydrogen storage.