Transport properties of gas diffusion layer of proton exchange membrane fuel cells: Effects of compression

Abstract The gas diffusion layer (GDL) is an essential component for a proton exchange membrane (PEM) fuel cell because it provides pathways for different transport processes, including gas diffusion, liquid permeation, and thermal/electrical conduction. However, the compact pressure applied on the fuel cell stack can lead to GDL deformation and thus a change of the transport properties. Therefore, this study numerically estimated the effect of compression on different transport properties of GDL. The anisotropic fibrous structure of GDL is first reconstructed by a stochastic orientation method. Then, the compression process is simulated by a finite element method to export a deformed GDL geometry for transport models. The variations of stress, porosity, and the transport properties with compression are validated. It is found that the compression reduces the oxygen diffusivity and intrinsic permeability, while improves the thermal and electrical conductivity of GDL. The transport property changes are proved larger in the in-plane direction than through-plane direction. By fitting the correlations of compression ratio with the transport properties, several correction factors are proposed. Furthermore, the sensitivity of different transport properties to compression level is analyzed. These results provide a deeper understanding and practical approach for the modification of GDL and PEM fuel cells.