The electrochemical reduction of CO₂ to CH₄ and C₂H₄ at Cu/Nafion electrodes (solid polymer electrolyte structures)

Abstract

The construction of copper/Nafion electrodes (solid polymer electrolyte structures) by an electroless plating method is described. These electrodes were used for the gas phase electrochemical reduction of CO₂ to hydrocarbon products, including CH₄ and C₂H₄. The faradaic efficiencies of the electrodes under ambient conditions with a counter solution of 1 mM H₂SO₄ at a potential of −2.00 V vs. SCE reached a steady-state value of about 20% after 30 min of electrolysis. This corresponded to a rate of total hydrocarbon production of approximately 9.8×10⁻⁷ mole h⁻¹ cm⁻². Increasing the potential of the electrode to more negative potentials, or increasing the proton concentration of the counter solution, caused a decrease in the faradaic efficiencies due to a relative increase in the rate of proton reduction vs. that of CO₂ reduction. If the proton concentration of the counter solution was decreased to an alkaline pH, hydrocarbon production quickly ceased because of proton starvation.