Theoretical exploration of Rh1/CeO2 catalysts with high performance using CO oxidation as a probe reaction

Abstract

Rh1/CeO2 attracts much attention in single-atom catalysis due to its unique catalytic performance and maximum atomic efficiency. Since different possible structures of Rh1/CeO2 coexist in real catalysts, it is hard to discriminate their catalytic roles and reaction mechanism due to the difficulty of preparing pure modeling catalyst. To solve this difficult problem, the adsorption and reaction behaviors of CO and O2 on four modeling catalysts of Rh1/CeO2 were systematically investigated by using density functional theory calculation in this work. The catalytic role and CO oxidation mechanism on Rh1/CeO2 catalysts were elucidated. On Rh1/CeO2(111), CO reacts with adsorbed O2 via Eley-Rideal mechanism; and the rate-determined step of CO oxidation cycle is CO reaction with the rest O atom of O2 with a barrier of 0.99 eV. On Rh1/CeO2-δ(111), CO reacts with activated O2 via Langmuir-Hinshelwood mechanism and continue the oxidation cycle via Rh1/CeO2(111). On RhxCe1-xO2, CO directly reacts with surface oxygen without barrier to form RhxCe1-xO2-δ; while the barrier of CO oxidation cycle on RhxCe1-xO2-δ is 1.18 eV. Upon the discrimination of the catalytic roles of Rh1/CeO2 catalysts with different structures, several important insights into design and development of Rh1/CeO2 catalysts with high oxidation performance were proposed.