Electrochemical Production of Oxalate and Formate from CO₂by Solvated Electrons Produced Using an Atmospheric-Pressure Plasma

In this work, we use an atmospheric-pressure plasma in argon as a cathode to electrochemically reduce carbon dioxide in aqueous solution. Using optical absorption spectroscopy, we directly show that solvated electrons reduce CO 2(aq) to form the carboxyl radical anion CO 2 − (aq) , and the reaction obeys 3D bulk reaction kinetics similar to those measured in radiolysis experiments. We then use liquid ion chromatography to show that the CO 2 − (aq) intermediate ultimately reacts to produce oxalate and formate. The overall faradaic efficiency of the reaction is close to 10% for a CO 2(aq) concentration of 34 mM. However, given the known reaction kinetics of solvated electrons, this efficiency should approach 100% as the concentration of CO 2(aq) is increased.