Proton Exchange Membrane Fuel Cell Performance Analysis and Optimization Research on Porosity Distribution of Diffusion Layer

The gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFC) plays a role in supporting and protecting the proton exchange membrane (PEM) and the catalyst layer (CL); it also provides channels for electron conduction and gas transport. Porosity, as its main parameter, the distribution size and distribution area of porosity affect the performance of the fuel cell. When studying the issue of nonuniform porosity distribution in the diffusion layer, the consideration of effective electrical conductivity is relatively scarce. Therefore, based on the theory of heat and mass transfer, this paper constructs a 3D model for numerical simulation by considering the influence of porosity on electrical conductivity and verifies the correctness of the model through experiments. Based on the model, this study investigates the porosity distribution that linearly varies along different directions and determines the optimal combination distribution in three directions using orthogonal experiments. The findings indicate that the porosity in regions 1 and 2 (the two regions adjacent to the water inlet and the flow channel side, respectively, after the diffusion layer is divided along the X, Y, and Z directions) of the GDL are critical factors influencing the cell’s performance. Through the optimized combination obtained in this study, the optimal porosity distribution structure was identified, which improves the fuel cell current density by 5.7% and reduces the oxygen distribution inhomogeneity by 39.48% compared to a uniform porosity structure. In comparison with the single-direction distribution, it can achieve a more uniform oxygen distribution at the interface between the cathode CL and the GDL while ensuring further improvement in current density.