Enhanced Electrochemical CO ₂ Activation via Oxygen Vacancy at the Interface of Inverted CeO ₂ /Ag Catalyst for Efficient CO Production

Electrochemical CO₂ reduction represents a sustainable negative carbon technology, yet its widespread application is hindered by sluggish reaction kinetics, particularly in the initial adsorption and activation of CO₂─the rate-determining step. Herein, we report an inverted Ag-based catalyst architecture in which CeO₂ nanoparticles are supported on metallic Ag, creating abundant CeO₂/Ag interfaces. These interfaces facilitate the formation of oxygen vacancies at CeO₂/Ag interfaces under reductive conditions while maintaining high electrical conductivity through the metallic Ag matrix. Kinetic analyses and density functional theory reveal that these interfacial oxygen vacancies significantly enhance the CO₂ activation and lower the activation barrier, thereby accelerating the overall CO₂RR kinetics. In situ Raman and attenuated total reflectance surface-enhanced infrared absorption spectroscopy directly confirm the generation and dynamic behavior of oxygen vacancies during electrolysis. Notably, alternating atmosphere experiments demonstrate reversible consumption and regeneration of oxygen vacancies upon exposure to CO₂ and inert gas, providing compelling evidence that oxygen vacancies actively participate in CO₂ activation. This work highlights the critical role of engineered metal-oxide interfaces and defect engineering in enhancing electrocatalytic CO₂ conversion.