Identification of CO₂ as a Reactive Reagent for C-C Bond Formation via Copper-Catalyzed Electrochemical Reduction

The electrochemical reduction of CO₂ (CO₂ER) holds great promise as a method to achieve carbon neutrality and revolutionize the utilization of fossil fuels. Advanced catalysts used in CO₂ER have demonstrated the ability to generate valuable multi-carbon products through the formation of carbon-carbon (C-C) bonds. Previous research has predominantly focused on C-C formation by dimerizing *CO or coupling *CO with other *C₁ intermediates. However, the potential coupling of CO₂ with *C₁ intermediates has not been explored experimentally or theoretically despite CO₂ being the exclusive reactant in CO₂ER and having a high concentration. This study employed DFT calculations and a constant electrode potential model to investigate the possibility of CO₂ + *C₁ couplings on Cu(100) surfaces. Surprisingly, the results indicate that CO₂ can serve as a favorable reagent for C-C bond formation, surpassing the reactivity of *CO under alkaline conditions. The enhanced reactivity of CO₂ compared to that of *CO was elucidated based on a barrier decomposition analysis. Experimental validation was conducted to confirm these theoretical results.