Hydrogen crossover in proton exchange membrane electrolysis cells under assembly compression: a one-dimensional multiphysics model and parametric structural design

It is widely acknowledged that proton exchange membrane electrolysis cells constitute the core technology for large-scale green hydrogen production from renewable energy sources. Hydrogen crossover in proton exchange membrane electrolysis cells poses critical safety and efficiency challenges, yet its quantitative correlation with assembly compression remains unclear. This study develops a one-dimensional steady-state model integrating gas-water-heat-charge transfer and electrochemical reactions, with a compression ratio variable to empirically correct transport coefficients and contact resistance. Results reveal that concentration-driven diffusion dominates hydrogen crossover (>90%) over 0–3.6 A/cm 2 . The compression ratio and operating temperature exert a synergistic enhancement effect on hydrogen crossover. Higher compression reduces contact resistance and improves efficiency, but also elevates mass transfer resistance and safety risk of hydrogen crossover. The gradient porosity configuration with high porosity (0.7) in the cathode porous transport layer and low porosity (0.3) in the cathode catalyst layer reduces the hydrogen concentration in oxygen by 46.5% under high-current operating conditions. The gradient hydrophilicity design, featuring a hydrophobic porous transport layer and a hydrophilic catalyst layer, increases the average membrane water content by 4.69%. This work deepens the understanding of the compression effect on the hydrogen crossover, and offering steady-state guidance for safe, efficient electrolyzer design.