Electrochemical reduction of high pressure CO2 at a Cu electrode in cold methanol

The electrochemical reduction of high pressure CO2 with a Cu electrode in cold methanol was investigated. A high pressure stainless steel vessel, with a divided H-type glass cell, was employed. The main products from CO2 by the electrochemical reduction were methane, ethylene, carbon monoxide and formic acid. In the electrolysis of high pressure CO2 at low temperature, the reduction products were formed in the order of carbon monoxide, methane, formic acid and ethylene. The best current efficiency of methane was of 20% at −3.0 V. The maximum partial current density for CO2 reduction was approximately 15 mA cm−2. The partial current density ratio of CO2 reduction and hydrogen evolution, i(CO2)/i(H2), was more than 2.6 at potentials more positive than −3.0 V. This work 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).