Enhancing Synergistic Water–Gas Management in PEMFCs Using Architected Microporous Layers with Pore-Size Gradients

Microporous layers (MPLs) play a pivotal role in proton exchange membrane fuel cells (PEMFCs) by regulating water management and reactant transport. However, conventional MPLs with single-sized pores lack the structural versatility to simultaneously meet the requirements for efficient gas transport and water removal, which severely limits the performance improvement of PEMFCs. This study fabricates an MPL with a graded pore structure through solvent-controlled differentiation and a stepwise coating–sintering process, which synergistically enhances capillary-driven gas supply and liquid water removal. Multiphysics simulations confirm that the gradient structure improves water drainage and gas diffusion, and this improvement is reflected in the superior performance of the graded MPL compared with conventional single-layer structures under varying backpressure conditions. The MPL with a graded pore structure exhibits the highest output performance of 1860 mW cm^–2 under hydrogen/air operation at a high relative humidity of 100%, representing an improvement of approximately 36.8% over the commercial MPL, and still delivers a 10.4% enhancement under 75% relative humidity. The notable performance gains achieved underscore the practical potential of the fabrication method, while our findings establish critical structure–transport correlations for MPL optimization in advanced PEMFCs.