Selectivity control by modifying pressure, temperature, and ionomer decoration for CO2 electroreduction using gas-diffusion Cu electrodes

"Beyond catalyst" factors influencing the performance of Cu-based CO2 electroreduction were investigated based on rigorous microkinetic analysis under industrially relevant conditions. Our experimental results indicated that the activity and selectivity of Cu-based CO2 electroreduction were not unaffected by electrolyte pH changes but were significantly influenced by operating conditions including pressure and temperature. Analyzing the kinetic data concerning CO2 partial pressure (PCO2) and operating temperature revealed that higher PCO2 (≥25 kPa) or higher reaction temperature (≤333 K) favored CO formation, coinciding with a reduction of the C2+ and formate pathways. Product distribution control at 333 K was achieved by engineering the structure of the Cu gas-diffusion electrode (GDE), where CO was exclusively produced on bare Cu, and the faradic efficiency of C2+ was enhanced by introducing an optimized Nafion ionomer content in the catalyst layer, likely ascribable to the modulation of diffusion coefficients of reactants (e.g., CO2 and H2O) and key intermediates (e.g., CO).