Electrochemical Reduction of CO 2 on a Cu Electrode under High Pressure: Factors that Determine the Product Selectivity

The selectivity of the electrochemical reduction products of on a Cu electrode in aqueous solution depended remarkably on the pressure (<60 atm), stirring condition, and the current density. As the flux of to the Cu electrode surface was increased by increasing pressure and/or by stirring, the main reduction product was changed in the order of and/or . On the other hand, the selectivity of the reduction products was changed in the order of and/or by increasing the current density. From these results, it was concluded that the balance between the flux of from the bulk solution to the electrode surface and the current density determines which reduction products are produced. Hydrocarbon formation was preferential when the current density was comparable to the maximum flux under given condition. The partial current density for maximum hydrocarbon formation occurred at 375 mA cm −2 under pressure at 30 atm.