Computational descriptor for electrochemical currents of carbon dioxide reduction on Cu facets

Computation screening is crucial for designing efficient electrochemical catalysts for carbon dioxide (CO₂R) reduction that produce valuable hydrocarbons and oxygenates. Herein, leveraging density functional theory calculations of the CO adsorption energy $\mathrm{\Delta }{E}_{\mathrm{C}\mathrm{O}}$$\mathrm{\Delta }{E}_{\mathrm{C}\mathrm{O}}$ on seventeen Cu terminations, we discover a strong linear correlation between $\mathrm{\Delta }{E}_{\mathrm{C}\mathrm{O}}$$\mathrm{\Delta }{E}_{\mathrm{C}\mathrm{O}}$ and the recently experimentally measured CO₂R electrochemical currents (ACS Catal. 2022, 12, 11, 6578–6588). Examining the ab initio thermodynamics of the early critical intermediates CO*, COH*, and CHO*, we find that CO* $\to$$\to$ CHO* is the thermodynamically controlling step. Beyond the general CO adsorption energy that only shows a linear trend with CO₂R activity, we show that the reaction free energy of CO* $\to$$\to$ CHO* is the descriptor for the overall CO₂R activity for Cu facets, as it displays a volcano relationship with the experimental current. Importantly, we show that increasing the step and kink density of the Cu terminations not only enhances CO adsorption strength but also modulates the CO* $\to$$\to$ CHO* pathway, as respectively exemplified in the (941) and (741) facets. In addition, we explain that the high activity of (741) is due to its relatively low hydrogen evolution reaction activity compared with the other Cu surfaces.