Selective ethylene formation by pulse-mode electrochemical reduction of carbon dioxide using copper and copper-oxide electrodes

Although the electrochemical reduction of carbon dioxide (CO2) with a copper electrode produces hydrocarbons, the activity toward the conversion of CO2 is lost for several 10 min by the deposition of poisoning species on the electrode. To solve the poisoning species problem, the electrochemical reduction of CO2 was carried out using a copper electrode with a pulse electrolysis mode with anodic as well as cathodic polarization. The anodic polarization intervals suppressed the deposition of poisoning species on the electrode, and the amount of two hydrocarbons, CH4 and C2H4, barely decreased even after an hour. By choosing appropriate anodic potential and time duration, the selectivity for the C2H4 formation was greatly enhanced. The enhancement was found to be due to the copper oxide formed on the copper electrode. The selectivity was further improved when the electrochemical reduction was made with the copper-oxide electrode. The highest efficiency of about 28% is obtained at -3.15 V.