Electrochemical reduction of high pressure carbon dioxide at a Cu electrode in cold methanol with CsOH supporting salt

The electrochemical reduction of high pressure CO2 at a Cu electrode in cold methanol was investigated with cesium hydroxide supporting salt. A divided H-type glass cell, which was placed in a high-pressure stainless steel vessel, was employed. The main products from CO2 by the electrochemical reduction were carbon monoxide, formic acid, methane and ethylene. The maximum current efficiency of CO was of 84% at −3.5 V. In the potential region more negative than −3.0 V, the efficiency of hydrogen formation, being a competitive reaction against CO2 reduction, was depressed to less than 2%. The partial current density ratio of CO2 reduction and hydrogen evolution, i(CO2)/i(H2), was more than 42 at potentials more negative than −3.0 V. This reserch can contribute to the large-scale manufacturing of useful material from readily available and inexpensive raw materials, CO2-saturated methanol from industrial absorbers (the Rectisol process).