Operando Investigation of Ag‐Decorated Cu 2 O Nanocube Catalysts with Enhanced CO 2 Electroreduction toward Liquid Products

Direct conversion of carbon dioxide into multicarbon liquid fuels by the CO 2 electrochemical reduction reaction (CO 2 RR) can contribute to the decarbonization of the global economy. Here, well‐defined Cu 2 O nanocubes (NCs, 35 nm) uniformly covered with Ag nanoparticles (5 nm) were synthesized. When compared to bare Cu 2 O NCs, the catalyst with 5 at % Ag on Cu 2 O NCs displayed a two‐fold increase in the Faradaic efficiency for C 2+ liquid products (30 % at −1.0 V RHE ), including ethanol, 1‐propanol, and acetaldehyde, while formate and hydrogen were suppressed. Operando X‐ray absorption spectroscopy revealed the partial reduction of Cu 2 O during CO 2 RR, accompanied by a reaction‐driven redispersion of Ag on the CuO x  NCs. Data from operando surface‐enhanced Raman spectroscopy further uncovered significant variations in the CO binding to Cu, which were assigned to Ag−Cu sites formed during CO 2 RR that appear crucial for the C−C coupling and the enhanced yield of liquid products.