Impact of Tortuosity on Species Transport in PEMFCs Gas Diffusion Layers

Abstract

Proton exchange membrane fuel cells (PEMFCs) are electrochemical systems that directly convert the chemical energy of hydrogen into electricity, offering high energy efficiency and low environmental impact. Within these systems, the gas diffusion layer (GDL) plays a critical role in ensuring efficient reactant transport and uniform current distribution. This study examines the influence of GDL tortuosity on PEMFC performance. A numerical model, incorporating the Maxwell-Stefan transport laws for multi-species diffusion, the Butler-Volmer equation for electrochemical kinetics, and Darcy’s law for flow in porous media, was developed using COMSOL Multiphysics. The main originality of this work lies in the explicit analysis of anisotropic tortuosity, contrasted with the isotropic case, in order to evaluate its effects on species transport and current density distribution. The results show that increasing tortuosity significantly limits reactant diffusion, leading to a reduction in cell performance of up to 20-80 % at low current densities. Polarization curve analysis indicates a decrease in cell efficiency as tortuosity increases. In addition, anisotropic tortuosity induces spatial heterogeneities in diffusion pathways, resulting in non-uniform current density distribution and further performance losses. These findings highlight the critical role of GDL microstructure in PEMFC operation and provide practical insights for the design and optimization of GDL materials. Specifically, controlling tortuosity and its anisotropy can improve reactant transport, enhance efficiency, and increase the durability of fuel cells under realistic operating conditions.