Co-electrospun hydrophobic gradient-structured catalyst layer for enhanced water management in fuel cells

Water flooding within catalyst layers (CLs) results in increased mass transfer loss and a significant performance degradation in proton exchange membrane fuel cells (PEMFCs). In this work, we leveraged the unique advantage of electrospinning to separately fabricate catalyst fibers and hydrophobic polyvinylidene fluoride (PVDF) fibers, thereby enhancing the consistency and controllability of CL fabrication. Using this approach, we developed a gradient hydrophobicity-modified nanofiber (GHM-NF) CL, in which the region close to the PEM exhibits relatively hydrophilic to maintain effective proton conduction, while the region adjacent to the gas diffusion layer is appropriately hydrophobic to enable efficient water expulsion. The power density of GHM-NF CL at 2.4 A cm −2 is 9.1% higher than that of the NF CL, accompanied by a 22.7% reduction in concentration resistance. The GHM-NF CL also demonstrates excellent drainage under higher Pt loading, where enhanced current densities and greater water production occur. Its power density at 3.5 A cm −2 reaches 1.239 W cm −2 , which is 8.9% higher than that of the NF CL. Meanwhile, at 3 A cm −2 , the concentration resistance of the GHM-NF CL is only 52.3 mΩ cm 2 , a 16.7% decrease compared to the NF CL (62.8 mΩ cm 2 ). Overall, this developed GHM-NF CL mitigates flooding and suppresses the sharp rise in mass transfer losses under high current densities and substantial water production, offering a promising new strategy for designing hydrophobic gradient CLs with high drainage capacity to meet the ever-increasing performance demands of commercial PEMFCs.