Highly ordered Nafion-silica-HPW proton exchange membrane for elevated temperature fuel cells

Well-ordered Nafion-silica-HPW proton exchange membranes with Nafion ionomers as co-surfactant have been synthesized through a facile self-assembly between the positively charged silica, negatively charged HPW acids, and Nafion ionomers. The results exhibited uniform nanoarrays with long-range order when Nafion content in the complex is lower than 30 wt%. The electrolyte stripe textures were clearly presented with an interval channel of 5–6 nm. The well-ordered proton conducting sites made the proton move through the membrane freely with low humidity dependence of proton transportation through the Nafion-silica-HPW electrolyte. The proton conductivities of the Nafion-silica-HPW electrolyte with Nafion content of 10–30 wt% were 0.018–0.022 Scm−1 at 25 °C without humidification, and the conductivities increased to 0.043–0.05 Scm−1 when the temperature increased to 200 °C. The capillary condensation of the ordered structure also improved the water uptake of the Nafion-silica-HPW electrolyte at low humidity. With external humidifying of 25 RH%, the water uptake of the Nafion-silica-HPW electrolyte with Nafion content of 10–30 wt% reached to 15–23 wt% at elevated temperature of 100–200 °C. The improvement of the water uptake facilitated proton transport through the Nafion-silica-HPW electrolytes, resulting in proton conductivities of 0.082–0.095 Scm−1 at temperature of 150–200 °C, 25 RH%.