Electrochemical Formation of C Products Steered by Bridge-Bonded *CO Confined by *OH Domains.

During the electrochemical CO reduction reaction (eCORR) on copper catalysts, linear-bonded CO (*CO) 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 (*CO) as an active species. By combining Raman spectroscopy, gas and liquid chromatography, and density functional theory (DFT) simulations, we show that adsorbed *OH domains displace *CO to *CO. The electroreduction of a CO+CO cofeed demonstrates that *CO distinctly favors the production of acetate and 1-propanol, while *CO favors ethylene and ethanol formation. This work enhances our understanding of the mechanistic intricacies of eCORR and suggests new directions for designing operational conditions by modifying the competitive adsorption of surface species, thereby steering the reaction toward specific multicarbon products.