Optimization of gas diffusion layer in high temperature PEMFC with the focuses on thickness and porosity

Abstract

Wide ranges of thickness (e.g. 100–400 μm) and porosity (e.g. 30–70%) of gas diffusion layer (GDL) in a high temperature proton exchange membrane fuel cell (HT-PEMFC) are available in the literature. However, the effects of GDL porosity and thickness on electron conduction and gas distribution uniformity (under the rib and under the channel) are unclear. In this study, a numerical non-isothermal 3D model was developed. After model validation, parametric analyses were performed to investigate the effects of thickness and porosity on flow uniformity (under the rib and under the channel), diffusion flux and ohmic resistance. It is found that both the flow uniformity and ohmic resistance increase with increasing thickness and porosity. However, the thickness and porosity have opposite influence on diffusion flux, which decreases with increasing GDL thickness but increases with increasing porosity. Unlike the previous research suggesting thin GDL with high porosity, optimal GDL thickness and porosity are found in the present study. The appropriate GDL thicknesses for anode and cathode are 80–120 μm and 140–170 μm respectively while the optimal value for GDL porosity is 35–45%. This study clearly demonstrates that we can further achieve a performance increment of 7.7% by carefully controlling the thickness and porosity of GDL.