Fabrication of sulfonated poly(aryl ether ketone sulfone) membranes blended with phosphotungstic acid and microporous poly(vinylidene fluoride) as a depository for direct-methanol fuel cells

• A series of composite membranes with a cell structure were prepared.
• The cell structure stabilizes HPW to maintain high proton conductivity.
• The composite membranes exhibited low methanol permeability coefficient.

A series of sulfonated poly(aryl ether ketone sulfone)/poly(vinylidene fluoride) phosphotungstic acid (SPAEKS/PVDF-HPW) composite membranes were prepared and characterized by Fourier transform infrared spectroscopy. No phase separation was observed by scanning electron microscopy. The HPW particles are evenly dispersed in the membranes, probably because the microporous structure of PVDF stabilized the dispersion of HPW particles in the membranes. Thermogravimetric analysis showed that the thermal stability of the membranes increased with increase in HPW content. Moreover, the composite membranes exhibited outstanding oxidative stability. The methanol permeability coefficient of the SPAEKS/PVDF-HPW10% membrane at 20 °C was 1.68 × 10−7 cm2 s−1, and the highest proton conductivity of the membrane at 80 °C was 0.098 S cm−1, slightly lower than that of Nafion® 117. However, the relative selectivity of the membrane was higher than that of Nafion® 117. The swelling ratio of the membrane at 80 °C was 16%, and the methanol uptake of the membrane at room temperature was only 10.2%, much lower than those of Nafion® 117. The results indicate that the SPAEKS/PVDF-HPW membranes can be used as an alternative proton exchange membrane for direct-methanol fuel cells.