Pathways for the Formation of C2+Productsunder Alkaline Conditions during the Electrochemical Reduction of CO2

Establishing how Cu facilitates the electro-chemical CO2reduction reaction (CO2RR) to C2+productsremains a critical challenge. Under typical reaction conditions,the pH near the electrode is considerably more alkaline thanthat in the bulk due to mass transport limitations. Challengeswith probing alkaline pathways using computational methodshave limited understanding of the CO2RR under experimen-tally relevant conditions. In this work, using the Volmerreaction on Cu (100), we demonstrate that predicted activationbarriers can substantially differ between acidic and alkalinepathways. We compute reaction energetics for alkaline*COprotonation andfind that, while the formation of*CHO ispreferred thermodynamically, the formation of*COH isfavored kinetically at high overpotential. However, wefind formation of*CHO via reaction of*H and*CO feasible atroom temperature. We report potential-dependent energetics for forming thefirst C-C bond in CO2RR andfind that COdimerization likely dominates. Finally, we investigate how long-range van der Waals interactions impact our results bycomparing to the meta-GGA B97M-rV.