Effect of CO 2 shortage on the Performance of Membrane Electrode CO 2 Electrolyzer

Abstract To mitigate greenhouse effects, carbon dioxide reduction reaction (CO2RR) has been used as an efficient means of carbon reduction. In CO2 electrolyzer, CO2 shortage can happen and degrade the reaction efficiency. Herein, an efficient and long-lived formic acid three-cell electrolyzer is used to study the effect of CO2 shortage, by operating the electrolyzer from full CO2 supply to CO2 shortage. In addition, the effects of various CO2 fluxes and concentrations on the electrolyzer current, acid concentration and lifetime are investigated. The results demonstrated that the electrolyzer current and the CO to H2 ratio both decreases from full CO2 to CO2 shortage, indicating that the reactivity of converting CO2 into formic acid ions is weakened. On the contrary, the hydrogen evolution reaction is intensified. Long-term CO2 shortage also cause the catalyst to detach and agglomerate in the cathode catalyst layer, reducing its active surface area and overall performance. Compared with the CO2 flux, the CO2 concentration exerts a more pronounced influence. To ensure the electrolysis efficiency, the carbon dioxide concentration should not be less than 80%.