Combined effects of microstructural characteristics on anisotropic transport properties of gas diffusion layers for PEMFCs

Gas diffusion layer (GDL) plays a key role in proton exchange membrane fuel cells, which provides multi-functions for gas transport, thermal-electrical conduction and mechanical support. Coupling manipulation of different microstructural characteristics could poten-tially improve transport properties of GDLs. This work proposes an approach to reconstruct heterogenous GDLs and conduct pore-scale modeling to evaluate the anisotropic transport properties. The models are reconstructed using X-ray computed tomography, stochasti-cally reconstruction methods and morphological processing techniques, which consider different fiber diameter, GDL thickness and local porosity distribution type. Combined ef-fects of microstructure characteristics on tortuosity, diffusivity, thermal-electrical con-ductivity and anisotropic ratios are investigated comprehensively. The results show that the diffusivity with fiber diameter of 7 mm is approximately 7% lower, and the conductivity is 8% higher than that of 9 mm. The anisotropic ratios of diffusivity, thermal conductivity and electrical conductivity range from 1.25 to 1.65, 5 to 20, and 20 to 55, respectively. Local porosity distribution of uniform-fluctuated type, fiber diameter of 7 mm and GDL thickness of 126 mm are suggested to balance diffusivity and thermal-electrical conductivity simul-taneously. The methods and results can guide microstructure design of other porous electrodes with higher performance.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.