Electrochemical reduction of carbon dioxide to ethylene at a copper electrode in methanol using potassium hydroxide and rubidium hydroxide supporting electrolytes

The electrochemical reduction of CO2 with a Cu electrode was investigated in methanol using potassium hydroxide and rubidium hydroxide supporting salts. The main products from CO2 were methane, ethylene, carbon monoxide and formic acid. The maximum current efficiency for ethylene was of 37.5%, at −4.0 V versus Ag/AgCl, saturated KCl in KOH/methanol. The typical ratios of current efficiency for ethylene/methane, rf(C2H4)/rf(CH4), were 2.3 and 6.7, in KOH/methanol and RbOH/methanol-based electrolytes, respectively. In KOH/methanol, the efficiency of hydrogen formation, a competing reaction of CO2 reduction, was depressed to below 3.3%. On the basis of this work, the high efficiency electrochemical CO2-to-ethylene conversion method appears to be achieved. Future work to advance this technology may include the use of solar energy as the electric energy source. This research can contribute to the large-scale manufacturing of fuel gases from readily available and inexpensive raw materials, CO2-saturated methanol from industrial absorbers (the Rectisol process).