Geometric design of gas diffusion layer of PEMFCs to improve water management using multiphase lattice Boltzmann method

• A 3D LBM-VOF pore-scale model was developed to study water transport in PEMFC GDLs. • Porosity, fiber diameter, contact angle, velocity, and geometry govern drainage and capillarity. • Reduced porosity and larger fibers enhance water removal but increase capillary pressure. • Mesh-based GDLs outperform fibers, providing faster drainage and lower water saturation. • Hexagon and MultiOctagon offer optimal trade-offs between drainage efficiency, and pressure. Proton exchange membrane fuel cells (PEMFCs) are considered an advanced technology for clean energy usage due to their high efficiency and zero emissions. However, effective water management in the gas diffusion layer (GDL), particularly the formation and removal of liquid water droplets, remains a major challenge. In this study, a three-dimensional two-phase flow model based on the lattice Boltzmann method combined with the volume of fluid (LBM-VOF) approach is developed using the Palabos platform to simulate droplet dynamics at the pore scale of the GDL. The model is validated against existing numerical and experimental data. The main novelty of this study is to show the impacts of key geometric parameters, including porosity, fiber diameter, contact angle, and inlet velocity for conventional fiber-based structures, followed by the report of the best-performing values. Results reveal that mesh-based geometries, especially the hexagonal arrangement, significantly enhance water removal. In particular, the MultiOctagon 70% and Hexagon 70% configurations reduce water saturation and removal time by 42.16% and 44.99%, and by 47.61% and 43.99%, respectively, compared to the random fiber-based structure with 70% porosity and 8 µm fiber diameter. These findings highlight the potential of GDL designs to improve water management and overall PEMFC performance.