Adsorption of Ni, Pd, Pt, Cu, Ag and Au on the Fe3O4(111) surface

The interaction of Group 10 and 11 transition metals with the magnetite (111) surface has been investigated using the GGA + U density functional theory and periodic slab surface models. It was found that these transition metals adsorb stronger on an oxygen-terminated magnetite (111) surface than on an iron-terminated surface. On an oxygen-terminated surface, the adsorption strength is in the order of Ni > Pt ~ Cu > Pd > Ag ~ Au. In contrast, the order on an iron-terminated surface is Ni > Pt ~ Cu > Au > Pd ~ Ag. The adsorption strength was found to correlate well with the average lengths of metal-oxygen bonds. The magnetite (111) surfaces largely modify the electronic structures of the transition metals. Compared to their density of states in bulk structures, the atomically adsorbed transition metals have narrower d bands, and their d-band centers are closer to the Fermi levels. This implies the higher activities of the atomically adsorbed transition metals.