Influence of Gradient Porosity Porous Transport Layer on Heat and Mass Transport Behavior of Proton Exchange Membrane Water Electrolyzer

Abstract A three-dimensional, nonisothermal electrochemical model, incorporating reconstructed pore structures, was developed to quantify how porous transport layer (PTL) microstructures regulate heat and mass transport in proton exchange membrane water electrolyzers (PEMWEs). Parametric simulations were conducted to evaluate the synergistic effects of anode inlet velocity, initial porosity, and porosity gradient. The results demonstrate that an inlet velocity of 0.6 m s − 1 effectively suppresses thermal hotspots and mitigates interfacial gas blockage, reducing liquid water retention by approximately 9%. An initial porosity of ∼ 0.5 optimizes the balance between convective transport and solid-matrix conductivity, yielding a 5% improvement in the reaction rate compared to low-porosity (0.2) designs. Furthermore, a subtle porosity gradient ( ∼ 0.15 ) maximizes hydrogen yield—increasing hydrogen saturation by ∼ 3.5 % —by sustaining stable capillary forces near the catalyst layer, whereas a moderate gradient (0.3–0.4) facilitates oxygen removal and enhances the overall current density. Conversely, excessive gradients ( > 0.4 ) compromise thermal uniformity. These findings establish quantitative benchmarks for tailoring PTL porosity distributions to significantly enhance PEMWE performance.