International Journal of Energy Research, Vol.37, No.8, 879-887, 2013
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 degrees C without humidification, and the conductivities increased to 0.043-0.05 Scm-1 when the temperature increased to 200 degrees 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 degrees 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 degrees C, 25 RH%. Copyright (c) 2012 John Wiley & Sons, Ltd.
Keywords:proton exchange membrane fuel cell;elevated temperature;ordered structure;self-assembly;capillary condensation