Gradient hydrophobicity and thickness regulation treatment of stacked microporous layers to improve proton exchange membrane fuel cell performance

In this paper, based on the principle of gradient aperture, a cathode gas diffusion layer with three microporous layers was prepared using conductive carbon black with three different particle sizes. The thickness of the microporous layers was studied, and a gradient hydrophobic structure was designed. The purpose was to maximize the output performance of the cell by adjusting the preparation parameters of the microporous layers. The physical and electrochemical properties of each sample showed that the change in micropore layer thickness redistributed the pore size distribution of the gas diffusion layer, especially increasing the number of pore sizes in the range of 20–40 µm. They improved the liquid water transport capacity of the gas diffusion layer at high current density. The gradient hydrophobic structure of the microporous layer promoted the cathode gas diffusion layer to expel liquid water in time and ensure the oxygen supply. The results showed that when the microporous layer thickness was 60 µm. The hydrophobic agent content in the three microporous layers was 10 wt%, 20 wt%, and 30 wt%, respectively, the limiting power densities of 0.883, 0.916, and 0.863 W/cm² could be achieved under the three humidity conditions of 40%, 60%, and 100%, respectively. The limiting power density increased by 17.1%, 12.0%, and 18.1%, respectively, compared with the samples with the same optimal thickness but no gradient hydrophobic structure.