Decrypting the Controlled Product Selectivity over Ag−Cu Bimetallic Surface Alloys for Electrochemical CO2 Reduction

Electrochemical CO2 reduction reaction (ECO2RR) with controlled product selectivity is realized on Ag−Cu bimetallic surface alloys, with high selectivity towards C2 hydrocarbons/alcohols (≈60 % faradaic efficiency, FE), C1 hydrocarbons/alcohols (≈41 % FE) and CO (≈74 % FE) achieved by tuning surface compositions and applied potentials. In situ spectral investigations and theoretical calculations reveal that surface‐composition‐dependent d‐band center could tune *CO binding strengths, regulating the *CO subsequent reaction pathways and then the product selectivity. Further adjusting the applied potentials will alter the energy of participated electrons, which leads to controlled ECO2RR selectivity towards desired products. A predominant region map, with an indicator proposed to evaluate the thermodynamic predominance of the *CO subsequent reactions, is then provided as a reliable theoretical guidance for the controllable ECO2RR product selectivity over bimetallic alloys. Ag−Cu surface alloys, as electrocatalysts for CO2 reduction, demonstrated controllable product selectivity when their surface compositions and the applied potentials were rationally tuned. The working mechanism of these catalysts was revealed by in situ spectral investigations and theoretical calculations. A predominant region map describing the thermodynamic predominance of *CO involved subsequent reactions is provided as reliable guidance for the design of catalysts for CO2 reduction towards value‐added products.