The redox properties of ceria make it suitable as a catalyst or support in oxidation reactions. Ceria-supported transition metal nanoparticles or isolated single atoms provide a metal-support interface that reduces the energy cost to remove interfacial oxygen atoms, providing active oxygen species that can participate in Mars van Krevelen oxidation processes. CO oxidation is a key probe reaction to test the reducibility of ceria-supported catalysts and is also practically important in the elimination of CO at relatively low temperatures in various applications. Preferential oxidation of CO (PROX) in excess H2 controls the CO concentration to ultra-low levels to prevent poisoning of hydrogen oxidation electrocatalysts. The reactivity of catalysts in CO oxidation and selectivity towards CO over H2 in PROX is dependent on the type and dispersion of metal species, the structural and chemical properties of CeO2, and the synthetic preparation methods of the catalysts. In this review, we summarize recently published works on catalytic CO oxidation and PROX reactions on ceria-supported metal nanoparticles and single atoms. We summarize the reactivity on different supported metals, and on different CeO2 surfaces with the same metal. We summarize the most likely reaction mechanisms as suggested by density functional theory calculations. The factors contributing to selectivity towards CO oxidation in PROX reactions on various supported metals are also discussed.
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