Electrochemical CO₂ Reduction on Copper in Propylene Carbonate

Abstract

Aqueous electrolytes are most commonly used for the CO2 reduction reaction (CO2RR), but suffer from a low CO2 solubility that limits the reaction. Electrochemical CO2 reduction in nonaqueous electrolytes can provide a solution, due to the higher CO2 solubility of organic solvent-based electrolytes. Herein, the product distribution of the electrochemical CO2 reduction on polycrystalline Cu in 0.7 m tetraethylammonium chloride in propylene carbonate with different water additions (0, 10, and 90 v%), and for different operating conditions (10, 25, 40, and 60 °C), is investigated. It is found that CO2 reduction on Cu in a propylene carbonate solution results in H2, CO, and formic acid formation only, even though Cu is known to produce C2+ products such as ethylene and ethanol in aqueous electrolytes. Increasing the operating temperature increases the CO2RR kinetics and shows an improvement in CO formation and decrease in H2 formation. However, increasing the operating temperature also increases water transport through the membrane, resulting in an increase of H2 formation over time when operating at 60 °C.