Tortuosity and Species Transport in PEM Fuel Cells Gas Diffusion Layers

Abstract

Proton Exchange Membrane (PEM) fuel cells are electrochemical devices that directly convert chemical energy of hydrogen into electricity, offering high efficiency and low environmental impact. Among the key components of PEM fuel cells, the Gas Diffusion Layer (GDL) plays a critical role in facilitating the transport of reactant gases and in ensuring uniform current distribution across the cell. This study investigates the influence of GDL tortuosity, a structural parameter characterizing the complexity of diffusion pathways on PEM fuel cells performances. COMSOL Multiphysics was used to develop numerical model and simulate the effects of isotropic and anisotropic tortuosity on (a) species transport and (b) current density distribution within the cell. The results indicate that higher tortuosity significantly impedes reactant diffusion, leading to performance degradation, especially under low current density. Polarization curves’ analysis confirms a marked decline in cell output with increased values of tortuosity. Furthermore, the study reveals that anisotropic tortuosity introduces non-uniform diffusion patters, affecting cells efficiency. These findings highlight the critical importance of GDL microstructure in PEM fuel cells design and suggest that optimizing tortuosity, alongside other parameters such as porosity, gas pressure, and conductivity, is essential for improving cells’ durability and performance in practical applications.