Analysis of temporal changes in hydrogen permeation during run-in phase of PEM water electrolysis lab short-stacks considering electro-osmotic drag

This work presents experimentally determined H₂ in O₂ concentrations from the first approximately 1000 h of atmospheric operation of proton exchange membrane water electrolysis lab short-stacks. These exhibit a run-in effect in the form of increasing H₂ gas permeation over the first few hundred hours, followed by stabilization. A model-based interpretation of the H₂ in O₂ data indicates an approximate doubling of both mass transfer coefficients, for the membrane and the cathode catalyst layer. Using two different membrane types with remarkably different electro-osmotic drag coefficients demonstrates that the consideration of convection in the model significantly influences the determined cathode mass transfer coefficient. However, the relative increase over time remains unchanged.