Ag Single Atoms Anchored on CeO2 with Interfacial Oxygen Vacancies for Efficient CO2 Electroreduction

Abstract

Ag single-atom catalysts (SACs) have great potential in selective electrocatalysis of the CO₂ reduction reaction (CO₂RR) to CO, while it is still a challenge to achieve high current density and high atom efficiency simultaneously. Here, we present a new and simple in situ adsorption–reduction method to prepare Ag SACs supported on CeO₂ (Ag₁/CeO₂). It is found that Ag single atoms are anchored on CeO₂ through strong metal–support interaction (SMSI), and each Ag atom is accompanied with three interfacial oxygen vacancies. This Ag₁/CeO₂ exhibits high performance in the electrocatalytic CO₂RR with a high CO faradaic efficiency (FE) of >95% under a wide potential range. The turnover frequency (TOF) value can reach 50,310 h^–1 at FE_CO = 99.5% in H-cells. Notably, Ag₁/CeO₂ achieves an industrial-grade current density of 403 mA cm^–2 with a high FE_CO of 97.2% in flow cells. Experimental results combined with density functional theory calculation revealed that this superior performance was mainly ascribed to the existence of interfacial oxygen vacancies, which lead to the formation of Ag–O–Ce³⁺ atomic interfaces, and activates the Ce³⁺–O structures as the synergistic active center of Ag, thus promoting CO₂ adsorption and activation and reducing the reaction potential barrier of *COOH-to-*CO.