Unveiling the kinetics of CO2 reduction in aprotic electrolyte: The critical role of adsorption

Abstract

Aprotic organic electrolytes for electrocatalytic CO2 reduction (CO2R) offer a promising yet little-explored alternative to avoid the selectivity issues of alkaline media. We present a model-assisted study of the local reaction environment at a Cu cathode in aprotic organic electrolytes to determine the kinetics of the CO2R and the kinetic limitations and reveal their dependence on reaction conditions. The adsorption of CO2 is identified as the rate-determining step, as opposed to the often-assumed electron transfer during radical anion formation. Unlike alkaline media, there is no transport limitation in aprotic media. Furthermore, our model predicts two strategies to overcome the adsorption limitation: (i) by increasing surface roughness and (ii) by elevating pressure. The findings highlight the critical role of CO2 adsorption on CO2R performance and enable knowledge-driven optimization of reaction conditions and electrocatalysts.