A Novel Fluorinated Graphite-Loaded Sulfonated Poly(ether ether ketone) Membrane with Enhanced Stability and Efficiency for Proton Exchange Membrane Fuel Cells

A membrane combining high proton conductivity and excellent durability is essential for proton exchange membrane fuel cells (PEMFCs). Sulfonated poly(ether ether ketone) (SPEEK) offers a low-cost alternative to Nafion but suffers from a trade-off between conductivity and dimensional stability. In this article, we report a fluorinated graphite (FG)-reinforced SPEEK composite membrane (SPEEK/FGx) that overcomes this limitation, while significantly enhancing tensile strength, oxidative stability, thermal stability, and power density. As a result, compared with pristine SPEEK, the SPEEK/FG0.5 membrane achieves 175% oxidative durability and a swelling ratio of only 29.4%, leading to a 6.8% increase in maximum power density in a single-cell PEMFC. Experimental and theoretical analyses reveal that the enhanced performance arises from the synergistic interplay between a newly formed hydrogen-bond network and the hydrophobic FG interface, which together optimize polymer chain structure and reconstruct efficient proton transport pathways.