Designing Flexible Carbon Nanofiber Membranes by Electrospinning and Cross-Linking for Proton Exchange Membrane Fuel Cells

Traditional carbon-based materials suffer from fragility, low mechanical strength, and electrical conductivity when they are used as a gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs), resulting in low power density. In this study, a flexible carbon nanofiber membrane (CFM) was studied for use as a GDL, prepared by polyacrylonitrile (PAN) electrospinning with the incorporation of carboxylated multiwalled carbon nanotubes (MWCNTs), polyethylenimine (PEI) impregnation, glutaraldehyde (GA) cross-linking, and thermal treatment. The concentrations of MWCNTs in the electrospinning solution and PEI in the impregnation solution were investigated. Interestingly, the mechanical strength and electrical conductivity of CFM showed a triangle trend with the MWCNTs or PEI concentration. The optimal sample (CNT1.5/PEI7/GA-CFM) demonstrated good flexibility, with an in-plane resistivity of 18.60 mΩ cm, a tensile strength of 7.94 MPa, and a bending strength of 20.65 MPa. The peak power density and maximum current density were respectively 1169 mW cm^-2 and 2720 mA cm^-2, exceeding those of commercial Toray and Cetech GDLs under identical testing conditions. These results illustrate the potential of high-performance electrospun CFMs for GDL applications.