Effect of reaction atmosphere on catalytic CO oxidation over Cu-based bimetallic nanoclusters on a CeO2 support

Understanding the nature of active sites and the catalytic properties of oxide-supported bimetallic clusters under reaction conditions remains challenging. In this study, we combine first-principles calculations with genetic algorithm and grand canonical Monte Carlo methods to reveal the structures and compositions of ${\mathrm{Ce}\mathrm{O}}_{2}$-supported $\mathrm{Cu}$-based bimetallic clusters in an oxygen-rich environment. Oxidized ${\mathrm{Cu}}_{4}{X}_{4}$ (X = $\mathrm{Pd}$, $\mathrm{Pt}$, and $\mathrm{Rh}$) bimetallic clusters on ${\mathrm{Ce}\mathrm{O}}_{2}(111$) are stable and exhibit different catalytic properties during $\mathrm{CO}$ oxidation compared with the pristine bimetallic clusters. Microkinetic simulations predict that ${\mathrm{Ce}\mathrm{O}}_{2}(111)$-supported ${\mathrm{Cu}}_{4}{\mathrm{Pd}}_{4}{\mathrm{O}}_{10}$, ${\mathrm{Cu}}_{4}{\mathrm{Pt}}_{4}{\mathrm{O}}_{11}$, and ${\mathrm{Cu}}_{4}{\mathrm{Rh}}_{4}{\mathrm{O}}_{14}$ clusters have much higher $\mathrm{CO}$ oxidation activity than the supported ${\mathrm{Cu}}_{4}{\mathrm{Pd}}_{4}$, ${\mathrm{Cu}}_{4}{\mathrm{Pt}}_{4}$, and ${\mathrm{Cu}}_{4}{\mathrm{Rh}}_{4}$ clusters; this is ascribed to the moderate $\mathrm{CO}$ adsorption strength and active oxygen on oxidized alloy clusters. A mechanistic study suggests that $\mathrm{CO}$ oxidation occurs via the ${\mathrm{O}}_{2}$ associative reaction mechanism on the ${\mathrm{Cu}}_{4}{\mathrm{Pd}}_{4}{\mathrm{O}}_{10}$ and ${\mathrm{Cu}}_{4}{\mathrm{Pt}}_{4}{\mathrm{O}}_{11}$ clusters, while it proceeds through the ${\mathrm{O}}_{2}$ dissociative reaction mechanism on the ${\mathrm{Cu}}_{4}{\mathrm{Rh}}_{4}{\mathrm{O}}_{14}$ cluster. Our calculations further predict that $\mathrm{CO}$ oxidation on the ${\mathrm{Cu}}_{4}{\mathrm{Rh}}_{4}{\mathrm{O}}_{14}$ cluster exhibits a low apparent activation energy, indicating that the oxidized cluster possesses excellent $\mathrm{CO}$ oxidation activity. This work demonstrates that the catalytic activity and reaction mechanism vary with the composition and oxidation state of the alloy nanocluster under the reaction conditions and emphasizes the influence of the reaction atmosphere on the reaction mechanisms and catalytic activity of oxide-supported alloy catalysts.