Electrochemical Formation of C2+ Products Steered by Bridge-Bonded *CO Confined by *OH Domains

During the electrochemical CO2 reduction reaction (eCO2RR) on copper catalysts, linear-bonded CO (*COL) is commonly regarded as the key intermediate for the CO-CO coupling step, which leads to the formation of multicarbon products. In this work, we unveil the significant role of bridge-bonded *CO (*COB) as an active species. By combining in situ Raman spectroscopy, gas and liquid chromatography, and density functional theory (DFT) simulations, we show that adsorbed *OH domains displace *COL to *COB. The electroreduction of a 12CO+13CO2 cofeed demonstrates that *COB distinctly favors the production of acetate and 1-propanol, while *COL favors ethylene and ethanol formation. This work enhances our understanding of the mechanistic intricacies of eCO(2)RR and suggests new directions for designing operational conditions by modifying the competitive adsorption of surface species, thereby steering the reaction toward specific multicarbon products.