Kinetic analysis makes the impossible possible: measuring CO adsorption free energies on the active sites during CO2 electroreduction

CO adsorption free energy (∆GCOads) was proposed as an important descriptor for CO2 electroreduction (CO2R), but this hypothesis has not been verified due to the lack of an experimental method that can measure ∆GCOads during CO2R. Herein, we develop a universal kinetic model combined with a rotating ring-disk electrode voltammetry method to estimate ∆GCOads on the active sites of various CO-producing catalysts during CO2R. We find CO adsorption is affected by the catalyst, cation identity, cation concentration, applied potential, and surface structure at CO2R condition. We also find that ∆GCOads difference is insignificant between Au and Cu, which cannot account for the observation that only Cu can catalyze CO2 to multicarbon products with substantial rates. This work highlights the complexity of evaluating CO adsorption at CO2R condition and provides an experimental approach based on kinetic analysis for measuring ∆GCOads on the active sites of CO-producing catalysts during CO2R.