High-shear restructuring of carbon black networks for durable and high-performance microporous layers in PEMFCs

The microporous layer (MPL), a key component of the gas diffusion layer (GDL), regulates gas transport, electron conduction, and water management in proton exchange membrane fuel cell (PEMFC). However, the relationship between intrinsic carbon black (CB) properties, high-shear dispersion processes, and the resulting MPL microstructure has not been systematically clarified. In this study, the effects of intrinsic CB properties and particle network restructuring induced by three-roll milling (TRM) on MPL performance were investigated. Three CBs were classified according to their electrical conductivity and shear-induced fragmentability. CB with high conductivity and high fragmentability (CB_HH) underwent effective fragmentation during TRM and recombined with PTFE to form a stable inter-particle network containing micro-, meso-, and macro-pores. This reconstructed network improved electrical stability and mass transport within the MPL. Consequently, the CB_HH-GDL exhibited only 4.6% resistance variation under repeated compression cycles. Fuel cell tests showed maximum current densities of 1090 and 1280 mA cm −2 at 50% and 100% relative humidity, respectively, representing improvements of over 55% at 50% relative humidity compared with CB with low conductivity and low fragmentability. These results highlight the importance of CB intrinsic properties and shear-induced network restructuring for designing durable and high-performance MPLs. • Carbon blacks were classified by conductivity and breakage under shear milling. • Carbon black networks influenced MPL compressibility and resistivity. • Three-roll milling restructured carbon black aggregates and inter-particle network. • CB_HH exhibited the highest conductivity and superior piezoresistivity. • High-shear dispersed CB_HH achieved improved current density and durability.