Oxygen vacancy formation energy at the Pd/CeO2(111) interface

The atomic and electronic structure of Pd adsorption on the unreduced and reduced ceria (111) surfaces is studied using first principles projector-augmented-wave (PAW) method based density functional theory (DFT) within generalized gradient approximation (GGA) and with the inclusion of on-site Coulomb interaction (GGA + U). It is found that there exist different adsorption features for Pd on different surfaces (unreduced and reduced): (1) on the unreduced CeO2(111) surface, Pd prefers to be adsorbed on the O-bridge site (O2-site); (2) on the reduced CeO2(111) surface, the adsorption is much stronger than that on the unreduced CeO2(111) surface; (3) the formation of an oxygen vacancy is easier at the Pd/CeO2(111) interface than that on the clean CeO2(111) surface, indicating that the Pd adatom enhances the oxygen storage capacity (OSC) of ceria, and the interaction between the palladium catalyst and the ceria support enhances the lower temperature activity of the catalyst. The mechanisms for this promotion in the OSC of ceria at the Pd/ceria interface are discussed.