Low-temperature, resin-free carbon papers with carbon nanotube bundles for gas diffusion layers in PEM fuel cells

초록

Flexible and electrically conductive carbon papers (CPs) were fabricated via a low-temperature (<= 350 degrees C), resin-free wet-laying process, in which carbon nanotube (CNT) bundles function as multifunctional physical binders interconnecting individual carbon fibers to form a continuous percolating network, eliminating the need for conventional resin binders and high-temperature carbonization. By systematically varying the CNT bundle content, well-defined correlations are established among microstructural evolution, electrical resistance, and gas permeability, with an optimized CP achieving the lowest area-specific resistance under compression while maintaining adequate gas permeability. PTFE coating imparts excellent hydrophobicity comparable to that of commercial SGL-22BB, and despite the absence of a microporous layer (MPL), X-CT image analysis and pore-scale simulations confirmed a more open pore structure, lower water breakthrough pressure, and faster water removal velocity than SGL-22BB, demonstrating that the highly porous CNT bundle network alone is sufficient to achieve superior liquid water management capability. Electrochemical evaluation revealed stable polarization performance across a wide range of relative humidity, outperforming SGL-22BB under high-humidity conditions, while EIS analysis confirmed superior mass transport characteristics at high current densities. Furthermore, the fabricated CPs exhibited excellent mechanical flexibility, withstanding sharp bending without cracking-in stark contrast to the brittle fracture behavior of commercial SGL-22BB. These results establish CNT bundle-reinforced CPs as a mechanically robust and electrochemically viable alternative to conventional carbonized gas diffusion layers, offering a scalable low-temperature fabrication route for next-generation PEMFC systems.

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