Ceria (CeO2) is an attractive catalyst because of its unique properties, such as facile redoxability and high stability. Thus, many researchers have examined a wide range of catalytic reactions on ceria nanoparticles (NPs). Among those contributions are the reports of the dopant-dependent catalytic activity of ceria. On the other hand, there have been few mechanistic studies of the effects of a range of dopants on the chemical reactivity of ceria NPs. In this study, we examined the catalytic activities of pure and Pr, Nd, and Sm-doped CeO2 (PDC, NDC, and SDC, respectively) NPs on carbon monoxide (CO) oxidation. Density functional theory (DFT) calculations were also performed to elucidate the reaction mechanism on rare-earth (RE)-doped CeO2(111). The experimental results showed that the catalytic activities of CO oxidation were in the order of CeO2 > PDC > NDC > SDC. This is consistent with the DFT results, where the reaction is explained by the Mars-van Krevelen mechanism. On the basis of the theoretical interpretation of the experimental results, the ionic radius of the RE dopant can be used as a simple descriptor to predict the energy barrier at the rate-determining step, thereby predicting the entire reaction activity. Using the descriptor, a wide range of RE dopants on CeO2(111) were screened for CO oxidation. These results provide useful insights to unravel the CO oxidation activity on various oxide catalysts.
Keywords: CO oxidation; ceria; density functional theory; doping; oxide catalyst; rare-earth.