Is Oxygen Diffusion Faster in Bulk CeO2 or on a (111)-CeO2 Surface? A Theoretical Study

Abstract Ceria (CeO2) is a promising metal-oxide support that is used in three-way catalysis (TWC). The activity of ceria-supported TWC depends on the location and concentration of oxygen vacancies. Oxygen diffusion can occur once the oxygen vacancy is created, and it leads to enhanced catalytic activity. In this study, the density-functional tight-binding method was used to estimate the free-energy barriers of oxygen diffusion in bulk CeO2 and on a (111)-CeO2 surface. The reconstructed free-energy surfaces from metadynamics sampling show that the diffusion in the bulk CeO2 is faster than that on the (111)-CeO2 surface, with activation barriers of 7.4 and 31.6 kcal/mol, respectively.