Unaccounted Impact of Diffuse Capacitance on Electrochemical Reduction of Carbon Dioxide

The electrochemical CO2 reduction reaction (CO2RR) relies on precise control of the catalyst and electrolyte environment so that an electric field from the Helmholtz-layer acts on reaction intermediates. Despite established benchmarking protocols, achieving reproducible performance remains difficult even for planar Cu under nominally identical conditions. We show that planar Cu operated at a fixed potential exhibits systematic variation in CO2RR activity and selectivity with counter-electrode po