Electrochemical reduction of carbon dioxide to hydrocarbons with high faradaic efficiency in LiOH/methanol

Abstract

The electrochemical reduction of CO2 with a Cu electrode in LiOH/methanol-based electrolyte was investigated. A divided H-type cell was employed, the supporting electrolytes were 80 mmol dm-3 lithium hydroxide in methanol (catholyte) and 300 mmol dm-3 potassium hydroxide in methanol (anolyte). The main products from CO2 were methane, ethylene, carbon monoxide, and formic acid. The maximum current efficiency for hydrocarbons (methane and ethylene) was of 78%, at -4.0 V vs Ag/AgCl, saturated KCl. The ratio of current efficiency for methane/ethylene, rf(CH4)/rf(C2H4), was in the range from 2.2 to 4.3. In LiOH/methanol, the efficiency of hydrogen formation, a competing reaction of CO2 reduction, was depressed to below 2% at relatively negative potentials. On the basis of this work, the high efficiency electrochemical CO2 to hydrocarbon 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). © 1999 American Chemical Society.