Two-stage electrolysis of H2O and CO2 to methanol: CO2-to-methane reduction at the cathode and subsequent methane-to-methanol oxidation at the anode

Abstract

Co-electrolysis of H₂O and N/C sources to valuable chemicals has the potential to contribute to global warming mitigation. We here report the electrochemical conversion of H₂O and CO₂ into methanol in a gas flow system at temperatures between 100 and 200 °C. CO₂ was reduced to methane with voltage-boosted H₂ at a Ru/C cathode. Introduced Fe₂O₃ nanoparticles promoted the adsorption and activation of CO₂ on the surface of Ru because of their high redox activity. Methane was oxidized to methanol through the formation of ˙CH₃ and active oxygen species at a Pt anode. The addition of Au to the anode enhanced the selectivity toward methanol by reducing the activity of Pt in the complete oxidation of methanol. Combining these processes with gas penetration into the electrolyte membrane enabled the synthesis of methanol from H₂O and CO₂, with a maximum faradaic efficiency of 54%. This work establishes a methodology for providing a good balance between the activity and selectivity of electrodes for the CO₂ reduction reaction.