Electrospun gas diffusion layers with reverse gradient pore structures for proton exchange membrane fuel cells under low humidity

For proton exchange membrane fuel cell (PEMFC) systems, the parasitic power loss can be decreased by removing the external humidifier. However, when the PEMFC system does not have an external humidifier, the maintenance of the PEMFC performance requires the use of gas diffusion layers (GDLs) with a good water-retention capacity. In this study, a reverse-gradient GDL suitable for PEMFC operation under nonhumidification conditions is fabricated using the electrospinning method. The reverse-gradient GDL is characterized by a decrease in the pore size from the catalyst layer to the flow-field plate. The breakthrough pressure and water saturation are tested using custom-made experimental apparatus, and the fluid transport mechanism is theoretically analyzed and simulated at the mesoscale. In addition, the single-fuel cell performance is tested to verify the effectiveness of the designed reverse-gradient structure. The theoretical analyses and mesoscale simulations show that the reverse-gradient GDL can retain more water in the fuel cell than the positive-gradient and uniform GDLs, and the PEMFC performance tests show that the reverse-gradient GDL can improve the water retention capacity and provide a higher power density under low-humidity conditions.