Kinetic Analysis Unlocks CO Adsorption Free Energies on the Active Sites during CO 2 Electroreduction

CO adsorption free energy (ΔG CO ads ) was proposed as an important descriptor for CO 2 electroreduction (CO 2 R), but this hypothesis has not been verified due to the lack of an experimental method that can measure ΔG CO ads during CO 2 R. Herein, we develop a universal kinetic model combined with a rotating ring-disk electrode voltammetry method to estimate ΔG CO ads on the active sites of various CO-producing catalysts during CO 2 R. We find CO adsorption is affected by the catalyst type, cation identity, cation concentration, applied potential, and surface structure at CO 2 R condition. We also find that the difference in ΔG CO ads determined on the active sites for CO 2 R-to-CO conversion between Au and Cu is insignificant, which cannot account for the observation that only Cu can catalyze CO 2 to multi-carbon products with substantial rates. This work highlights the complexity of evaluating CO adsorption at CO 2 R condition and provides an experimental approach based on kinetic analysis for measuring ΔG CO ads on the active sites of CO-producing catalysts during CO 2 R.