Tracking a Common Surface-Bound Intermediate during CO2-to-Fuels Catalysis

Rational design of selective CO2-to-fuels electrocatalysts requires direct knowledge of the electrode surface structure during turnover. Metallic Cu is the most versatile CO2-to-fuels catalyst, capable of generating a wide array of value-added products, including methane, ethylene, and ethanol. All of these products are postulated to form via a common surface-bound CO intermediate. Therefore, the kinetics and thermodynamics of CO adsorption to Cu play a central role in determining fuel-formation selectivity and efficiency, highlighting the need for direct observation of CO surface binding equilibria under catalytic conditions. Here, we synthesize nanostructured Cu films adhered to IR-transparent Si prisms, and we find that these Cu surfaces enhance IR absorption of bound molecules. Using these films as electrodes, we examine Cu-catalyzed CO2 reduction in situ via IR spectroelectrochemistry. We observe that Cu surfaces bind electrogenerated CO, derived from CO2, beginning at −0.60 V vs RHE with increasing ...