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 Mon CeO2(100) are compared with those of Mon CeO2(111) and CeO2(110). (c) 2013 Elsevier B.V. All rights reserved.