Electrochemical reduction of carbon dioxide with lead cathode and zinc anode in dry acetonitrile solution

The electrochemical reduction of carbon dioxide (CO2) is investigated in acetonitrile with tetrabutylammonium perchlorate as an electrolyte using a lead cathode and a sacrificial zinc anode, and the product under such a setup is insoluble zinc oxalate at potentials between -2.2 and -2.8 V vs. Ag rod electrode. Preelectrolysis is an effective method to remove the water in the electrolyte, which makes a distinct reduction peak of CO2 appear at -2.6 V vs. Ag on cyclic voltammogram. Even trace amounts of water in the electrolyte can interfere with the faradaic efficiency of reduction of CO2 to oxalate, and the product could be beta-ZnC2O4 (in anhydrous solution) or ZnC2O4 center dot 2H(2)O (if water exists). The faradaic efficiency for oxalate production also depends on the cathode potential and the temperature, and the maximum is 96.8 % at -2.6 V vs. Ag and 5 A degrees C. This is the highest value of CO2 electrochemical reduction found in the literature under ambient pressure.