Effect of Electrochemical Cell Design on the Ionic Conductivity and Oxygen Permeability Determination of Gas Separators

Electrochemical properties of gas separators, holding a potential for the application in alkaline electrolysis, such as ionic conductivity and impermeability for hydrogen and oxygen gases, are significantly influencing the efficiency of alkaline electrolysis. Both non-zero gap and zero gap atmospheric pressure laboratory scale test set-up, operating at room temperature, were developed in order to undertake a comparative study of their advantages and disadvantages for the lab scale electrochemical characterization of gas separator materials. The zero gap cell was able to provide a more accurate ionic conductivity of the separators via Electrochemical Impedance Spectroscopy (EIS). The non-zero gap cell set-up, coupled with Quadrupole Mass Spectrometer (QMS), enabled the quantitative assessment of the oxygen crossover of different separators. The influence of a long term immersion in 25 wt. % KOH determined using the non-zero gap cell, showed increased conductivity with immersion duration for asbestos, while the highly hydrophobic PPS and PPS with PTFE separators’ conductivity was not affected by longer immersion.