Passivation-driven gas diffusion layer degradation in PEM water electrolyser: Mechanism, performance impact and design strategy

Proton exchange membrane water electrolyser (PEMWE) is a promising technology for large-scale green hydrogen production and fuel decarbonisation. However, degradation of the anodic gas diffusion layer (GDL) significantly increases cell voltage and reduces efficiency, thereby limiting PEMWE durability and economic competitiveness for industrial deployment. Previous studies have primarily focused on mitigating GDL degradation and extending component lifetime, while the GDL degradation process itself has received limited attention. In this study, an experimentally validated multiphysics macroscale (mm-scale) PEMWE model combined with a quasi-steady state simulation framework is developed to investigate the GDL degradation process and its influence on PEMWE performance. The results reveal that TiO 2 film growth at the GDL-ACL interface follows a distinct spatial evolution sequence, initiating at the edges of the GDL solid under the bipolar plate (BPP) rib, propagating towards the GDL solid junctions, and eventually extending to GDL solid under the BPP flow channel. The GDL degradation process exhibits accelerating behaviour with increasing operating time, leading to progressively increased GDL-ACL interface contact resistance (ICR), non-uniform current and oxygen generation rate distributions, local oxygen accumulation, and increasing cell voltage. Furthermore, the GDL physical structure optimisation mitigates GDL degradation and improves PEMWE long-term performance and efficiency preservation. The cell voltage increase under severe GDL degradation condition is reduced by approximately 36.9 %. Overall, this study provides mechanistic insights into GDL degradation process in PEMWE and offers practical guidance for designing high-efficiency and durable green hydrogen production systems.