Tailoring Proton Transport in s‐PVDF‐HFP Membranes Through MOF Integration: A Route to Nafion‐Free Fuel Cell Electrolytes

ABSTRACT Developing durable, Nafion‐free proton exchange membranes (PEMs) with high proton conductivity and long‐term chemical resilience remains a critical challenge in fuel cell technology. In this work, sulfonated PVDF‐HFP composite membranes incorporating variable loadings of sulfonated Fe‐MIL‐88B‐NH 2 (5, 7, and 9 wt.%) were synthesized to investigate the influence of MOF dispersion on mechanical integrity, oxidative stability, and proton‐transport behavior. Structural analysis revealed that low to moderate MOF incorporation significantly improved the membrane microstructure by introducing well‐connected hydrophilic channels while maintaining polymer flexibility. Mechanical testing demonstrated that 5 and 7 wt.% composites displayed enhanced ductility and toughness compared to pristine polymer, whereas excessive loading (9 wt.%) led to filler agglomeration, promoting premature failure. Proton conductivity measurements showed a clear temperature‐activated conduction mechanism, with the 7 wt.% membrane exhibiting the highest conductivity across all temperatures. Although the lowest activation energy was observed at 9 wt.% loading, the 7 wt.% membrane exhibited the highest conductivity due to optimized microstructure and transport pathways. Nyquist impedance spectra further supported these findings, showing minimal bulk resistance for the 7 wt.% membrane. Additionally, oxidative stability tests demonstrated that controlled MOF dispersion enhances resistance to radical‐induced degradation, with the 7 wt.% composite offering the best balance between stability and performance. Overall, this study highlights the critical role of optimized MOF distribution in achieving high‐performance composite PEMs and establishes PHF‐MIL88‐7 as a promising candidate for Nafion‐free fuel cell applications.