Electrochemical reduction of CO2 using Cu electrode in methanol/LiClO4 electrolyte

• CO2 reduction at more negative potential under high pressure.
• Enhanced Faradaic Efficiency for CH4 formation at more negative potential.
• More reduced product in presence of Li+.
• Role of Li+ on the formation of H2 during CO2 reduction.

Electrochemical reduction of CO2 under high pressure in cold methanol (243 K) medium containing LiClO4 as supporting electrolyte was studied using Cu wire electrode. The major reduction products formed were methane, CO, ethylene and HCOOCH3. The experiments were carried out at different operating potential ranging from −3.0 to −4.0 V and the results were discussed in terms of their faradaic efficiencies. The different applied potentials employed invariably favored methane formation in the presence of Li+, at 243 K and 4 atm and, among which, the most negative potential (−4.00 V) showed relatively better efficiency than the less negative potentials. However, the H2 formation, an undesirable reduction product, was found to be as high as 60.2% at −4.00 V. The effective formation of methane and CO were discussed in terms of influence of the size of the cation of the supporting electrolyte used.