Electrochemical reduction of CO and H2 from carbon dioxide in aqua-solution

This study examined the characteristics of continuous operation in a continuous flow planar electrode reactor, such as Faradaic efficiency, selectivity, and products ratio of carbon dioxide. A silver electrode was found to be useful for the selective formation of carbon monoxide by the electrochemical reduction of carbon dioxide in aqueous electrolytes. The products (CO, H2) were analyzed by gas chromatography, which was equipped with a thermal conductivity detector (TCD), and the Faradaic efficiency and selectivity were calculated from the data. The yield of monoxide carbon increased with decreasing temperature but the hydrogen yield decreased. The carbon monoxide yield was higher at the lower range of electrolyte concentrations. A graph of the yield as a function of the electrode potential showed a negative parabolic curve. The maximum value is shown at −1.8 V vs. SCE. The optimized carbon monoxide to hydrogen ratio was obtained under the following conditions using a silver electrode: a 0.1 M KHCO3 electrolyte, 20 °C and a potential of −1.8 V vs. SCE.