Activation of Oxygen on the Surface of the Co3O4 Catalyst by Single-Atom Ag toward Efficient Catalytic Benzene Combustion

Supported noble metal-based catalysts have been extensivelystudied for catalytic benzene combustion during the past decade because oftheir high activity. Despite the enormous significance of noble metal-basedmaterials as benzene combustion catalysts, the key properties of catalyticactive sites and the plausible benzene combustion mechanism are a matter ofdebate. Herein, a well-defined model catalyst consisting of single Ag atomsdeposited on Co3O4oxide surfaces has been prepared and used to providemechanistic insights into the benzene combustion mechanism and the originsof the excellent reactivity of Ag. The single-atom Ag-on-Co3O4catalystexhibits excellent activity and stability for benzene combustion.T100(temperature required to reach 100% conversion of benzene) is achievedat 204 degrees C. Scanning transmission electron microscopy reveals that single Ag atoms on Co3O4are anchored to Co3+vacancy sites onthe support surface. Single-atom Ag incorporates excess oxygen and activates abundant Ag-O-Co bonds for reaction with benzene,thereby enhancing catalytic activity. The plausible benzene combustion path over the single-atom Ag-on-Co3O4catalyst is proposedto be benzene -> phenolate -> quinone -> maleate -> acetate -> CO2+H2O. The rate-limiting step is located in the maleate -> acetate -> CO2+H2O cycle at a temperature of 200 degrees C. The feasibility of this reaction pathway was confirmed from diffusereflectance infrared Fourier transform spectroscopy experiments. We anticipate that these observations will improve ourunderstanding of surface chemical processes in heterogeneous catalysis and provide useful information for the rational design ofhigh-performance catalysts for benzene combustion reactions.

Automated summary

In this study, a well-defined model catalyst consisting of single Ag atoms deposited on Co3O4 oxide surfaces was prepared, and the mechanism of benzene combustion and the source of excellent reactivity of Ag were revealed. The single-atom Ag-on-Co3O4 catalyst exhibited excellent activity and stability for benzene combustion. The plausible benzene combustion path over the catalyst was proposed. These findings are significant for understanding surface chemical processes in heterogeneous catalysis and for the rational design of high-performance catalysts.