Lattice Boltzmann simulation of the structural degradation of a gas diffusion layer for a proton exchange membrane fuel cell

Abstract

The aging of a gas diffusion layer (GDL) significantly impacts water drainage and mass diffusion within a proton exchange membrane fuel cell (PEMFC). This study employs a stochastic algorithm to reconstruct a 2D microstructure of carbon fiber-type GDL with various different aged degrees. Subsequently, a multiphase lattice Boltzmann method (LBM) is employed to examine water transport within the reconstructed GDLs. Results support the finding that as the GDL ages, its water elimination performance remarkably decreases and much water is retained inside the GDLs. Compared with the degradation of carbon fibers, the degradation of polytetrafluoroethylene (PTFE) leads to a more hydrophilic GDL, thereby reducing the local capillary pressure and forming multipaths for water transport, resulting in a more severe water flooding problem. A proper increase in PTFE content favors GDL antiaging performance, but an excessively high content can occupy pores and reduce the effective porosity, thus reducing the fuel cell performance. These results demonstrate that GDL with a PTFE content of 10 wt% shows better antiaging performance and the highest effective porosity. The study here provides an accurate assessment of liquid water drainage performance of GDL with various different aged degrees and guideline for designing GDLs with high antiaging performance.