Influence of Copper Surfaces on CO2 vs. CO C−C Coupling Efficiency

Abstract

CO₂ electrochemical reduction (CO₂ER) powered by renewable electricity is critical for transitioning to a carbon-neutral society by transforming CO₂ into essential commodities and fuels. The formation of multi-carbon compounds through C−C coupling reactions is crucial due to their high energy density and broad industrial uses. Traditionally, C−C coupling was believed to occur through the reaction of *CO (surface-bound CO) with *C₁ intermediates (surface-bound hydrocarbons with one carbon atom produced during CO₂ER). In this study, we used DFT calculations combined with a constant electrode potential model to discover a preference for CO₂+*C₁ over conventional *CO+*C₁ coupling on three commonly observed copper surfaces including Cu(111), Cu(110), and Cu(100). This result demonstrates that CO₂ is a more efficient carbon source than *CO for coupling with *C₁. Among the nine *C₁ species investigated, *CHO, *CHOH, *C, *CH, and *CH₂ show greater reactivity towards CO₂+*C₁ couplings on all the surfaces. Thus, enhancing CO₂ER efficiency necessitates increasing the surface concentrations of these five *C₁ intermediates, and several strategies have been proposed to accomplish this goal.