Charge transfer and formation of Ce3+ upon adsorption of metal atom M (M = Cu, Ag, Au) on CeO2 (100) surface

Adsorption behavior of metal atom M (M = Cu, Ag, Au) on CeO2(100), a technologically important catalytic support surface, is studied by using first-principles density-functional theory calculations with the on-site Coulomb interaction taken into account (DFT + U). Prior to geometry optimization, small distortions in selected Ce–O distances are imposed to explore the energetics associated with reduction of Ce4+ to Ce3+ due to charge transfer to Ce during M adsorption. Results indicate that the adsorption is accompanied by an electron charge transfer between neutral metal atom and neighboring Ce4+ cation. For the same adsorption site, there exist multiple adsorption configurations with the excess electron localized at various nearest neighboring Ce ion relative to the M. The order on adsorption energies of M on CeO2(100) surface follows: Cu > Au > Ag. The atomic and electronic structures of M on CeO2(100) are compared with those of M on CeO2(111) and CeO2(110).

► Adsorption of M (M = Cu, Ag, Au) on CeO2(100) causes in charge transfer from M to Ce.
► For the same adsorption site, there exist multiple adsorption configurations.
► Our theoretical results are compared wherever possible with experiment.