Electronic states of metal (Cu, Ag, Au) atom on CeO2(1 1 1) surface: The role of local structural distortion

Abstract

Surface structures and electronic states of metal (M=Cu, Ag and Au) adsorbed on CeO2(111) surface have been investigated using first-principles density-functional theory calculations with the on-site Coulomb interaction taken into account. Results indicate that the adsorption is accompanied by an electron charge transfer between neutral metal atom and neighboring Ce4+ cation. Charge redistribution with electron localized on the various Ce cations neighboring to adsorbed atom is observed and can be attributed to local structural distortion effects. For the same adsorption site, the structural configuration with the electron localized on the surface Ce cation away from the adsorbed metal atom M is energetically favorable. The strongest adsorption interaction for Cu and Ag is located at 3-fold subsurface O-top site, whereas 2-fold surface O-bridge site is the most stable for Au adsorption. The order on the adsorption energy follows the sequence of Cu>Ag>Au, indicating that Cu atom has a stronger interaction with CeO2(111) surface than Ag and Au. Previous controversies about the localization of the transferred electron and the valence state of the adsorbed Au atom have been successfully clarified via analysis of the local structural distortions.