Microstructural Thermo-Hydraulic Optimization of Microporous Layers for Enhanced Transport in High-Load PEM Fuel Cells

The performance of proton exchange membrane fuel cells (PEMFCs) operating at high current densities is severely limited by coupled mass transport, water management, thermal regulation, and hydraulic resistance phenomena occurring within porous transport layers. Among these components, the microporous layer (MPL) plays a critical role in controlling oxygen delivery, liquid water evacuation, heat dissipation, and interfacial transport stability; however, its microstructural optimization under high-load conditions remains insufficiently understood. Therefore, this study develops a comprehensive three-dimensional non-isothermal two-phase multiphysics model to investigate and optimize MPL microstructural characteristics for enhanced PEMFC performance. The model simultaneously couples electrochemical kinetics, multicomponent species transport, liquid water dynamics, porous momentum transport, heat transfer, and membrane hydration behavior under realistic operating conditions. Key MPL parameters, including porosity, thickness, permeability, tortuosity, pore diameter, wettability, and thermal conductivity, were systematically evaluated within a multi-objective thermo-hydraulic optimization framework. The optimized MPL architecture achieved approximately 63% improvement in power density, nearly 74% exergy efficiency, up to 96% water removal effectiveness, and more than 60% reduction in cathode pressure losses compared with the baseline configuration. Furthermore, significant improvements in oxygen accessibility, thermal uniformity, membrane hydration stability, and electrochemical activity distribution were observed. The results demonstrate that coordinated microstructural optimization effectively mitigates transport limitations associated with high-current-density operation and substantially enhances PEMFC efficiency and operational robustness. This work establishes an integrated microstructural design methodology for advanced MPL engineering and provides practical design guidelines for the development of next-generation high-performance PEMFC systems for transportation, stationary power, and clean-energy applications.