Enhancing water transport performance of gas diffusion layers through coupling manipulation of pore structure and hydrophobicity

The water discharge capacity of gas diffusion layer (GDL) is a key factor for improving the performance of proton exchange membrane fuel cells (PEMFCs) at high current density. In this study, the hydrothermal decoration approach is employed to enhance the hydrophobicity of a commercial GDL and is compared with the immersion method. The hydrophobic SiO₂ particles are homogeneously deposited on the carbon fiber of the GDL via hydrothermal decoration (HD-GDL). In contrast, the hydrophobic SiO₂ only partially coats the carbon fiber in the top and bottom regions of the GDL during the immersion (IM-GDL). The surface roughness and diameter of fibers increase when the surface morphology of fibers changes from grooves (CR-GDL) to coating (IM-GDL) and particles (HD-GDL). The breakthrough pressure is higher and the liquid water saturation ratio is lower for HD-GDL than that for CR-GDL and IM-GDL. Multi-scale numerical simulations show that the enhanced water transport velocity is due to the enlarged fiber diameter, whereas the decreased liquid water saturation ratio is due to the coupled effects of enhanced fiber hydrophobicity and enlarged fiber diameter. The improved water discharge capacity of the GDL induced by hydrothermal decoration can be employed to enhance the water management performance of PEMFCs.