Revisiting Active Site Quantification in CO2 Electroreduction: The Case for CO Displacement

The selectivity and geometric current density of copper-based electrodes for electrochemical CO2 reduction (CO2RR) has been significantly improved, yet research is striving to improve the intrinsic activity of these materials. The accurate quantification of active sites is vital to benchmark the intrinsic activity of the catalysts for electrochemical CO2 reduction to facilitate activity improvements. Herein, we propose a method to determine the active sites using CO displacement in potassium phosphate buffer at 10 oC. Comparing this method with the electrochemical surface area (ECSA) measured by double later capacitance, the most used technique in this field, we demonstrate that CO displacement provides a much more accurate quantification of the number of active sites. By normalizing current density vs the CO displacement active sites, we have confirmed electropolished copper foil has the highest intrinsic activity towards CO2RR. The paper further highlights the relationship between surface roughness and chained products.