Numerical investigation of microporous layer structure on mass transport and durability in proton exchange membrane water electrolyzers

Abstract

Proton exchange membrane water electrolyzers (PEMWEs) are considered a core technology for high-purity hydrogen production and renewable energy integration. Their performance and durability are strongly governed by electrode microstructural design. To address systematic studies on the role of the microporous layer (MPL) in electrolyzers gap, we develop a two-dimensional, two-phase, multiphysics-coupled model to investigate how MPL location, thickness, porosity, and wettability affect electrolysis performance, oxygen distribution, and the pressure difference across the membrane. The results show that the effect of the anode MPL is significantly stronger than that of the cathode, effectively improving oxygen distribution uniformity by 16.3%, reducing liquid water saturation at the anode, and optimizing gas–liquid co-transport. Increasing the MPL thickness markedly enhances the oxygen mole fraction in the catalyst layer and improves distribution uniformity; however, excessive thickness or extreme hydrophobicity/hydrophilicity leads to performance deterioration. More importantly, the presence of the anode MPL reduces the transmembrane gas pressure difference by up to 50%. In addition, the thickness, porosity, and hydrophobicity synergistic optimization can improve efficiency while enhancing safety and durability at high current densities. The optimal AMPL parameters are proposed as the thickness of 50–90 μm, contact angle of 80°, and porosity of 0.2–0.3. This study provides theoretical insights and practical guidance for electrode microstructural design in PEMWEs, with important implications for large-scale applications.