Operando Investigation of Ag-Decorated Cu₂ O Nanocube Catalysts with Enhanced CO₂ Electroreduction toward Liquid...

Direct conversion of carbon dioxide into multicarbon liquid fuels by the CO₂ electrochemical reduction reaction (CO₂ RR) can contribute to the decarbonization of the global economy. Here, well-defined Cu₂ O nanocubes (NCs, 35 nm) uniformly covered with Ag nanoparticles (5 nm) were synthesized. When compared to bare Cu₂ O NCs, the catalyst with 5 at % Ag on Cu₂ O NCs displayed a two-fold increase in the Faradaic efficiency for C₂₊ 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 Cu₂ O during CO₂ 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 CO₂ RR that appear crucial for the C-C coupling and the enhanced yield of liquid products.