The Role of Phase Mixing Degree in Promoting C‐C Coupling in Electrochemical CO2 Reduction Reaction on Cu‐based Catalysts

Cu‐based catalysts have been identified as the most promising candidates for generation of C2+ products in electrochemical CO2 reduction reaction. Defect engineering in catalysts is a widely employed strategy for promoting C‐C coupling on Cu. However, comprehensive understanding of defect structure‐to‐activity relationship has not been obtained. In this study, controllable defects generation is achieved, which leads to a series of Cu‐based catalysts with various phase mixing degrees. It is observed that the Faradaic efficiency toward C2+ products increases with the phase mixing degree, reaching 81% at maximum. In‐situ infrared absorption spectroscopy reveals that the catalysts with higher phase mixing degree tend to form *CO more easily and possess higher retention of *CO under high overpotential window, thereby promoting C‐C coupling. This work sheds new light on the relationship between defects and C‐C coupling, and the rational developed of more advanced Cu‐base catalysts.