Optimization of Microporous Layer Composition at Varying Humidities for High-Performance Polymer Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) is a promising energy supply device. Its improvement on output performance has always been a main subject. Microporous layer (MPL) is the water management center of PEMFC, which has an important influence on the mass transfer process and performance of PEMFC under high current density. In this paper, the performance of GDL based on Toray-H-060 with different carbon powder and C:PTFE of MPL were tested and optimized. SEM and static contact Angle was used to investigate Characterization of GDLs. The polarization curve was used to select the best performance, and EIS was used to explore the internal optimization mechanism. The output performance increases with humidity from 25%RH to 75%RH for all four samples. The MPL sample formulated with C: PTFE = 8:2 and XC-72 powder is the best under wide humidity region, and the best performance is achieved at 75%RH. The maximum power density reaches 0.949W/cm² at 1.8A/cm². At 100%RH, because of dense structure, the GDL of Toray substrate has poor output performance and low maximum power density of PEMFC, because of cathode flooding under high humidity conditions. The increasement of MPL hydrophobicity, achieved by change of carbon powder and PTFE content, contributes to the decrement of mass transfer resistance at high current density. The equilibrium between proton conductivity and water management is essential to ensure improved fuel cell performance. In summary, this study is useful for understanding influence of MPL contents on mass transfer performance in PEMFC and can guide the composition design of MPL.