Electrochemical Reduction of CO2 on Modified Cu Electrodes Resulting from Pre-Electroreduction Annealed Cu in Different Electrolytes

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In this paper, the modified Cu electrodes were prepared by annealing Cu foil in air and then electrochemically reducing the resulting Cu oxide layers in different electrolytes. The CO2 reduction activities of these electrodes were found to be strongly dependent on the annealing temperature and annealing time. Therefore, the effects of both annealing condition and pre-electroreduction in different solutions on electroreduction of CO2 were investigated on modified Cu electrodes. The modified Cu, donated as Cu-a, Cu-b, Cu-c, which electrochemically reduced in H2SO4, H3PO4 and NaOH, respectively, performed a favorable current density for CO2 reduction at a lower overpotential, and the current density reached about 80 mA cm-2 when the modified Cu reduced in H3PO4 at -1.5V vs Ag /AgCl, while about 76 mA cm-2 and 46 mV cm-2, for modified Cu reduced in H2SO4 and NaOH, respectively. For annealing conditions, the Cu foil after annealed at 500oC for 6h gave the best catalytic activity toward CO2 reduction regardless of pr-electroreduction in different solutions. In all cases, the modified electrodes perform a stable current density during the electrolysis time.