High-strength and dual thermal-electrical conductive modified carbon paper based on MWCNTs-CFs hierarchical architecture for fuel cells

In proton exchange membrane fuel cells(PEMFC), carbon paper is demanded to possess robust mechanical strength, high electrical and thermal conductivity, and optimized porosity for gas/water transportation. Conventional materials frequently fall short of meeting these requirements. Herein, multi-walled carbon nanotubes(MWCNTs) were integrated into the carbon paper by pre-impregnation to enwrap carbon fibers, thereby enhancing the fiber-resin bonding and mechanical properties of the carbon paper. Simultaneously, the MWCNTs form additional branching networks within the conductive and thermal skeleton established by the carbon fibers, strengthening both electrical and thermal pathways. At an optimal MWCNTs impregnation concentration of 3 wt%, the modified carbon paper achieved tensile and flexural strengths of 26.54 MPa (a 38.2 % increase) and 25.12 MPa (a 289.5 % increase), respectively, compared to conventional carbon paper (19.21 MPa, 6.45 MPa). Its in-plane and through-plane thermal conductivities improved to 19.14 W/(m·K) and 0.81 W/(m·K), surpassing conventional values (12.96 W/(m·K), 0.11 W/(m·K)). PEMFC simulations confirmed that the enhanced thermal conductivity reduces the peak operating temperature and improves temperature uniformity across the membrane. The modified carbon paper also exhibited lower resistivity (5.8 mΩ·cm) and increased the peak power density of the fuel cell by 112.9 % (1255.9 vs. 589.8 mW/cm²). These advancements enhance the efficiency, stability, and lifespan of the fuel cell, demonstrating significant application potential in the practical fuel cells systems.