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CO oxidation at ceria surfaces has been studied for decades, and many efforts have been devoted to understanding the effect of surface reduction on the catalytic activity. In this work, we theoretically studied the CO oxidation on the clean and reduced CeO2(111) surfaces using different surface cells to determine the relationships between the reduction degrees and calculated reaction energetics. It is found that the calculated barrier for the direct reaction between CO and surface lattice O drastically decreases with the increase of surface reduction degree. From electronic analysis, we found that the surface reduction can lead to the occurrence of localized electrons at the surface Ce, which affects the charge distribution at surface O. As the result, the surface O becomes more negatively charged and therefore more active in reacting with CO. This work then suggests that the localized 4f electron reservoir of Ce can act as the “pseudo-anion” at reduced CeO2 surfaces to activate surface lattice O for catalytic oxidative reactions. |
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