CuNiZn Vs CuZn Electrodes: Electrochemical CO2 Reduction, Role of Metal Elements, and Insights for C–C Coupling Chemistry

Exploring bi- and trimetallic catalysts in electrochemical CO2 reduction (EC CO2R) has been a focal point for discovering reduction products. This study investigates the distinct roles of metal elements in the CO2R using CuNiZn and CuZn electrodes. Bimetallic CuZn exhibits superior electrochemical activity, yielding substantial amounts of CO, CH4, C2H4, and various liquid products, including formate, ethanol, acetate, propanol, and isopropanol. The study on trimetallic CuNiZn suggests potential connections to Fischer-Tropsch (FT) synthesis, indicating their capability to produce long-chain hydrocarbons (CnH2n and CnH2n+2, n = 2-7) from CO2. EC CO reduction validated the FT process over the bi- and trimetallic catalysts. The discussion explores mechanisms for the formation of CO, CH4, and C-C coupled C2+ products, considering potential- and concentration-dependent Faradaic efficiencies (FEs). Recycling tests emphasize the influence of metal composition on FEs. Surface analyses reveal oxidation states and compositional changes, while the dissolution of metals during electrochemistry highlights dynamic surface characteristics. This work provides insights into the metal composition of bi- and trimetallic catalysts, surface states, and electrochemical conditions, advancing our understanding of these electrodes and their role in CO2 recycling through electrochemistry.