Combined Effect of Catholyte Gap and Cell Voltage on Syngas Ratio in Continuous CO2/H2O Co-electrolysis

Electrochemical devices are constructed for continuous syngas (CO + H 2 ) production with controlled selectivity between CO 2 and proton reduction reactions. The ratio of CO to H 2 , or the faradaic efficiency toward CO generation, was mechan-ically manipulated by adjusting the space volume between the cathode and the polymer gas separator in the device. In particular, the area added between the cathode and the ion-conducting polymer using 0.5 M KHCO 3 catholyte regulated the solution acidity and proton reduction kinetics in the flow cell. The faradaic efficiency of CO production was controlled as a function of the distance between the polymer separator and cathode in addition to that manipulated by the electrode potential. Further, the electrochemical CO 2 reduction device using Au NPs presented a stable operation for more than 23 h at different H 2 :CO production levels, demonstrating the functional stability of the flow cell utilizing the mechanical variable as an important operational factor.