Theoretical Insights into Propene Epoxidation on Au₇/Anatase TiO_2–x(001) Catalysts: Effect of the Interface and Reaction Atmosphere

Abstract

Interfacial synergy of metal/oxide catalysts has been extensively studied in heterogeneous catalysis but elucidating the synergy mechanism and controlling the interfacial structure remain challenging. Herein, the effect of interface and reaction atmosphere on propene epoxidation on Au 7 /anatase TiO 2−x (001) catalysts is studied using density functional theory calculations. The results indicate that propene epoxidation occurs on the topmost Au atoms on a perfect Au 7 /TiO 2 (001) catalyst. Propene epoxidation with O 2 alone has a higher barrier and reaction energy, whereas in the presence of H 2 , the hydrogenation of O 2 to OOH is a feasible pathway for propene epoxidation from both kinetic and thermodynamic viewpoints. On defective Au 7 /TiO 2−x (001)-V O catalysts, oxygen vacancy regulates the geometric/electronic structures of interfacial sites, and propene epoxidation instead occurs at the interface of Au 7 and TiO 2−x (001)-V O . Under O 2 atmosphere, O atom fills the oxygen vacancy and significantly reduces the energy of the entire catalytic system; however, this has little effect on the kinetics of epoxidation. An O 2 −H 2 mixture results in the lowest barrier owing to the activation of the O−O bond and interfacial synergy. Our results suggest that the moderate and rational regulation of oxygen vacancy on the oxide surface can provide highly active sites and better interfacial synergy for propene epoxidation and highlight the essential role of the reaction atmosphere, which can be utilized to design high-efficiency heterogeneous catalysts.