Performance of Proton Exchange Membrane Water Electrolysis Based on Catalyst Layer Thickness: Experiment and Modeling

Abstract The increasing penetration of renewable energy, particularly hydropower, creates opportunities for green hydrogen production to utilize surplus electricity and provide long-term storage. Proton exchange membrane water electrolyzers (PEMWEs) are well suited for this due to their fast response and high current density, but deployment is limited by the scarcity and cost of iridium-based anode catalysts. This study investigates the effect of IrO 2 anode loading, expressed as catalyst layer (CL) thickness, on PEMWE performance. CCMs with four different thicknesses/loadings (2, 0.3, 0.1, 0.05 mg/cm 2 ) were tested over a range of temperatures. Polarization curves show performance generally decreases with thinner layers, yet the 0.05 mg/cm 2 loading maintains surprisingly high performance. A two-dimensional PEMWE COMSOL model incorporating SEM-measured catalyst-layer thicknesses for higher loadings (2, 0.3, and 0.1 mg/cm 2 ) and a scaled estimate for the 0.05 mg/cm 2 case was validated against experimental data, reproducing the observed performance trends.