Oxide-derived low-coordination Ag catalyst enables efficient photovoltaic-driven electrochemical CO2 reduction in MEA electrolyzers

Abstract

Oxide-derived silver (Ag) catalysts have emerged as promising candidates for achieving highly efficient electrochemical CO2 reduction reaction (eCO2RR) to CO at industrial current densities. However, the evolution of active site configurations, the atomic-level coordination-activity relationship, and the design of practical solar-driven systems remain insufficiently explored. In this work, we report the facile in-situ electrochemical synthesis of Ag2O-derived Ag (Ag2O-D-Ag), where the presence of unsaturated (low-coordination) Ag sites is revealed through operando X-ray absorption spectroscopy. The Ag2O-D-Ag catalyst exhibits a CO Faradaic efficiency of 90% at 500 mA cm-2 and maintains a stability over 100 hours at 200 mA cm-2 in a 4-cm2 membrane electrode assembly (MEA) electrolyzer. In-situ Fourier-transform infrared spectroscopy, combined with theoretical calculations, shows that these optimally low-coordinated Ag sites reduce the formation energy barrier for the *COOH intermediate, thereby accelerating the CO production. Integration of this catalyst with a photovoltaic module enables a 100-cm2 MEA prototype to operate stably for more than 30 hours, achieving a solar-to-CO energy efficiency of 4.87%. This study provides mechanistic insight into active site dynamics and demonstrates a scalable, renewable-energy-driven eCO2RR system.