Membrane Creep Caused by Porous Transport Layer Compression in PEM Water Electrolysis and the Impact on Hydrogen Permeation

Reducing hydrogen crossover is important for safe operation of polymer electrolyte membrane (PEM) water electrolyzers. The influence of catalyst coated membrane (CCM) properties, operating conditions, and cell assembly on hydrogen crossover have already been investigated. Recent investigations show strong pressure gradients in test cells used. Additionally, mechanical analysis shows membrane creeping under comparable pressure conditions. These findings raise the question whether the membrane creep during cell operation has an impact on hydrogen crossover. The present study addresses this question and presents results that show correlations between contact pressure, membrane creeping, and hydrogen crossover. CCMs were installed in a commonly used test cell with different contact pressure conditions. Because membrane creeping depends on its swelling state, some of the CCMs were installed wet. The influence of the different assembly modes on cell performance, hydrogen permeation, and membrane creeping were investigated. The study shows a strong dependence of the membrane thickness distribution on the installation situation of the CCM after several hours of operation. The contact pressures commonly used in PEM water electrolysis can lead to strong membrane creep during operation of the CCM, independent of electrochemical reactions. The higher the contact pressure, the stronger the membrane creep and the hydrogen crossover.