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

Electrochemical CO 2 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 CO 2 ─the rate-determining step. Herein, we report an inverted Ag-based catalyst architecture in which CeO 2 nanoparticles are supported on metallic Ag, creating abundant CeO 2 /Ag interfaces. These interfaces facilitate the formation of oxygen vacancies at CeO 2 /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 CO 2 activation and lower the activation barrier, thereby accelerating the overall CO 2 RR 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 CO 2 and inert gas, providing compelling evidence that oxygen vacancies actively participate in CO 2 activation. This work highlights the critical role of engineered metal–oxide interfaces and defect engineering in enhancing electrocatalytic CO 2 conversion.