Hybrid inorganic-organic nanocomposite polymer electrolytes based on Nafion and fluorinated TiO2 for PEMFCs

In this report, three hybrid inorganic-organic proton-conducting membranes based on a novel fluorinated titania labeled TiO2F dispersed in Nafion were prepared. The mass fraction of TiO2F nanofiller ranged between 0.05 and 0.15. The water uptake and the proton exchange capacity of the membranes were determined; the membranes were further characterized by TG, DMA and FT-IR ATR investigations. Finally, the hybrid membranes were used in the fabrication of membrane-electrode assemblies (MEAs), which were tested in operating conditions as a function of the back pressure and of the hydration degree of the reagents streams. It was demonstrated that, with respect to pristine recast Nafion, at 25%RH the MEA fabricated with the membrane including a mass fraction of TiO2F equal to 0.10 yielded a higher maximum power density (0.206 W cm−2 vs. 0.121 W cm−2). Finally, it was proposed a coherent structural model of this family of hybrid membranes accounting for both the properties determined from “ex-situ” characterizations and for the performance obtained from measurements in a single fuel cell in operating conditions.

► Three proton-conducting membranes based on Nafion and fluorinated TiO2 have been prepared. ► The water uptake is reduced, while the mechanical properties are improved with respect to Nafion. ► The fuel cell performance of the best membrane is improved with respect to Nafion at all hydration degrees. ► A model is proposed to correlate the thermomechanical and structural features with the fuel cell performance.