State-of-health of a CuCl electrolyzer during a 168-h test

A state-of-health test of a CuCl/HCl electrolytic cell was carried out by maintaining a constant current density of 0.3 A cm^-2 for 168 h at 80 °C and ambient pressure. While the most common method used to characterize the electrochemical performance of a CuCl electrolytic cell is to record current-voltage (I-V curves), it is also essential to separate the electrochemical and ohmic components of the polarization curve. In our study, the AC impedance characteristics of a single cell were studied along with the DC polarization curves. After the durability test, the potential required to maintain the cell at 0.3 A cm^-2 increased from 630 mV of the fresh membrane electrode assembly (MEA) to 710 mV due to some degradation processes in the electrolytic cell. Quantitative analysis of the performance decay was carried out by Electrochemical Impedance Spectroscopy (EIS). EIS measurements showed an increase in the area specific ohmic resistance of the MEA from 0.6 cm² to 0.85 cm² and area specific charge-transfer resistance from 0.61 cm² to 0.8 cm² measured at an overpotential of 0.2 V. The degradation in the cell is attributed to the decrease in membrane conductivity and an increase in the charge-transfer resistance.