CO Spillover Is Not a Promoter for C─C Bond Formation in CO ₂ Electroreduction on Cu‐Ag Bimetallic Catalysts

ABSTRACT Cu‐based bimetallic catalysts have been shown to improve the multi‐carbon (C ₂₊ ) selectivity in CO ₂ electroreduction, with the assumption that CO spillover from the CO‐selective catalysts to adjacent Cu domains via their bimetallic interface promotes C–C coupling. Here, through systematically controlling the Cu‐Ag interface densities of bimetallic catalysts, we report that CO spillover via the bimetallic interface is unlikely to enhance the formation of C ₂₊ products. Conversely, the abundant Cu‐Ag interface preferentially promotes CH ₄ formation while suppressing C─C bond formation. CO stripping studies also reveal that the Cu‐Ag interface does not favor C─C coupling. Further computational modelling suggests that Cu‐Ag bimetallic interface significantly enhances the energy barrier of CO dimerization while lowering the energy barrier for ^* CO hydrogenation toward CH ₄ , thus inhibiting C─C coupling toward C ₂₊ products while facilitating CH ₄ formation.