Employment of online conductivity measurements as a diagnostic tool of perfluorosulfonic acid membrane degradation in PEMWE

Abstract

Membrane degradation is one of the most important factors limiting lifetime of PEMWE stacks, and imposes severe purity demands in water fed into PEMWE electrolyzers. Therefore, damage to the membrane is one of the major limitations that impede widespread implementation of PEM technology to produce green hydrogen. Several membrane degradation test procedures have been discussed in literature. In this work, the loss of membrane material is related to the operating conditions of a 4-cell PEMWE stack through measurements of the fluoride concentration of the water output from the electrolyzer, both at the cathode and at the anode, at different temperatures (25 and 40 ºC), flow rates (20, 25 and 30 mL/min for a nominal water consumption of 2 mL/min) and operating loads (3 different voltages and currents ranging from the nominal 8 V and 0.26 A/cm2 to 6.8 V and 0.05 A/cm2). Conductivity of excess water collected at electrolyzer outlets is shown to be linearly related to its fluoride content under a wide range of electrolyzer operating conditions, including constant and dynamical loads. Therefore, knowing the on-line conductivity at both the anode and cathode can provide an assessment of the condition and lifetime of the membrane. The study shows that different workloads affect the lifetime of the electrolyzer and can be observed by in situ and ongoing monitoring of the conductivity of both the anode and cathode.