Spectroscopic Insights Into the Role of the Coverage of *Co and *H on Bifurcation of Ethylene and Ethanol Pathways in Carbon Dioxide Electroreduction

As key reaction intermediates involved in the electroreduction of carbon dioxide, *CO and *H (* represents active center) prove to be critical in regulating the selectivity toward different carbonaceous products. However, how the coverage of *H and *CO affects the selectivity of ethylene and ethanol remains unclear. In this work, we judiciously control the coverage of *CO or *H intermediates by introducing foreign metal into Cu nanoparticles, with the synthesis of four copper-based bimetallic catalysts, including CuAg, CuZn, CuCo, and CuPd. Four catalysts, together with Cu nanoparticles, are subjected to the electrochemical reduction of carbon dioxide in an H-cell. The CuZn catalyst is identified as the most effective catalyst for C─C coupling, exhibiting a Faradaic efficiency of 34.5% for C₂₊ products at −1.09 V versus RHE and a current density of −30.4 mA cm⁻². In contrast, CuPd catalyst inclines to catalyze C─C coupling toward ethanol, with an FE_ethanol/FE_ethylene ratio reaching up to 1.15. The coverage of key intermediates is investigated through in situ Raman spectroscopy. The doping of Ag and Zn metals can enhance the adsorption of *CO on the catalyst, while the doping of Co and Pd metals can enhance the adsorption of *H on the catalyst. Hence, the increased *CO coverage on Ag- and Zn-doped CuNP promotes C₂₊ generation, and the increased *H coverage of Co- and Pd-doped CuNPs enhances the C₂H₅OH/C₂H₄ ratio.