Enhancing the Comprehensive Performance of Proton Exchange Membrane Fuel Cells through a Novel Aramid Nanofiber/Cellulose Nanofibers Grafted with Methyl Methacrylate-Modified Carbon Paper

As the critical gas diffusion layer in proton exchange membrane fuel cells (PEMFCs), carbon paper (CP) governs the charge transfer, mechanical integrity, and gas/water transport. However, conventional CP struggles to simultaneously optimize permeability, strength, and conductivity, hindered by structural defects from resin expansion and weakened fiber-resin bonds during fabrication. To overcome this, a novel synergistic modifier: aramid nanofibers (ANF) and cellulose nanofibers grafted with methyl methacrylate (CNFM) within the phenolic resin (PF) were used to prepare CP. Investigating ANF:CNFM ratios revealed enhanced PF dispersion stability and modified thermochemical properties. The modified CP exhibited a tunable surface morphology, mechanical strength, in-plane resistivity, and pore characteristics, peaking at ANF:CNFM (3:1). Crucially, this modification inhibited PF methylene bridge fracture, increased polycondensation sites, and fostered a more ordered carbon matrix (reduced ID/IG: 2.12 vs 2.16 unmodified). Assembled PEMFCs with optimized ANF:CNFM (3:1) modified CP achieved a peak power density of 1.34 W·cm–2 (2 N·m, 60 °C anode humidification), surpassing commercial CP by 15.51% (1.16 W·cm–2). Lower mass transport impedance, confirmed by EIS, underscores the superior gas–liquid transport enabled by a tailored pore structure and enhanced mechanical strength, advancing high-performance PEMFCs design.