Impedance analysis of gas diffusion electrode for novel soda electrolysis

When a gas diffusion electrode is used in high concentrated alkaline solution at the high temperature, the electrolyte solution penetrates to the gas supply layer in the gas diffusion electrode. Penetration of the alkaline solution decreases the electrode performance. The cathodic properties of oxygen reduction on the gas diffusion electrode were examined by AC impedance method. The effects of electrode compositions, such as PTFE content and catalyst species of Ag and Pt on the electrode performance, were clarified by AC impedance technique with different kinds of the electrodes. The effect of the penetration of the electrolyte into the gas-diffusion electrode was determined quantitatively by using the charge transfer resistance and the double layer capacitance, corresponding to the catalyst consuming on the reaction layer and the wettability of the electrode in high concentrated alkaline solution at high temperature. Under one-month electrolysis test, the overpotential of the gas diffusion electrode increased by only 100mV, but the double layer capacitance increased by 50% degree and the charge transfer resistance increased to 5 times of the initial one. In acceleration test using ELAT, the changes in the electrode performance with time are clarified by using impedance parameters. In acceleration test, the double layer capacitance and the charge transfer resistance increased with deterioration of the gas diffusion electrode, and were 5 times and 30 times larger than the initial values respectively.