Meta-aramid fibrids as dual-functional initial bridging and dispersing agents for high-integrity carbon fiber paper in PEMFCs

• Meta-aramid fibrids (MAF) enable dual functions of dispersion and bridging in CFPs. • Ultra-thin CFPs with thicknesses down to 150 µm are successfully fabricated. • MAF-assisted paper formation provides a basis for continuous roll-to-roll CFP manufacturing. Carbon fiber paper (CFP), a crucial macroporous substrate of gas diffusion layers (GDLs) in proton exchange membrane fuel cells (PEMFCs), often suffers from fiber agglomeration and poor sheet uniformity due to the intrinsic low dispersibility and weak interfacial adhesion of carbon fibers (CFs). Herein, a facile and scalable strategy is proposed by introducing meta -aramid fibrids (MAF) as an initial physical bridging agent during slurry preparation to regulate CF dispersion and network formation. Benefiting from their excellent water dispersibility and fibrillated morphology, MAF physically intertwines with CFs, enabling the formation of a stable and self-supporting wet mat and thereby establishing a robust and operable fibrous framework for subsequent resin impregnation and pyrolysis. With an optimized MAF content of only 5 wt% relative to the mass of CFs, the resulting CFP exhibits a highly uniform microstructure, significantly improved gas permeability, and high electrical conductivity, while reducing the need for additional dispersants and binders. Moreover, optimization of MAF content and CFP thickness further enhances mass transport characteristics within the electrode. This study demonstrates a cost-effective and industrially viable approach for fabricating high-performance CFP, and highlights the crucial role of MAF in regulating fiber dispersion and network integrity for next-generation PEMFC applications.