In the global push toward carbon neutrality, proton exchange membrane (PEM) water electrolysis is regarded as a key pathway for coupling renewable electricity with large-scale green hydrogen production. In the multi-cell stack complex coupled multiphysics processes, including two-phase flow, electrochemical kinetics, and thermal–electrical interactions, occur and often uneven flow distribution, hotspot formation are induced In this study, a three-dimensional multiphysics model of a four-cell PEM electrolyzer stack (5 cm × 5 cm active area) was developed, incorporating flow field plates, porous transport layers, membrane electrode assemblies, and distribution manifolds.By using COMSOL Multiphysics 6.0, equations of charge, mass, momentum, heat, and water transport were solved, and the numerical model was validated through experimental comparison. The results indicate that U-type manifolds provide superior temperature management (18 K differential) compared to Z-type (29 K with localized hotspots). Polarization curve analysis for U-type stacks indicates d that increasing operating temperature from 60 °C to 80 °C will reduce cell voltage by approximately 0.4 V at 2.5 A cm⁻² (~5 % improvement), enhancing efficiency but increasing thermal management demands. These findings demonstrate that manifold geometry, flow distribution, material properties, and operating parameters are strongly coupled, requiring integrated multiphysics optimization to balance performance, safety, and durability in industrial-scale PEM electrolyzer design.
 

Proton exchange membrane electrolysis stack, Multi-physics model, Parameter distribution, Manifold types