Epoxy-polystyrene-silica sol–gel membranes with high proton conductivity by combination of sulfonation and tungstophosphoric acid doping

摘要

New hybrid electrolytes based on 2-allylphenol (AP), (3-glycidoxypropyl) trimethoxysilane (GPTMS) and\udtetraethoxysilane (TEOS) have been synthesized by sol–gel method and organic polymerisation. Proton\udconductivity has been endowed on the base of three strategies: a high concentration of hydroxyl\udgroups from the inorganic component, SO3\ud− groups through sulfonation of phenyl rings, and incorporation\udof tungstophosphoric acid (PWA). The system AP–GPTMS–TEOS doped with PWA allows to obtain\udhomogeneous, flexible, transparent and crack-free membranes after sulfonation of phenyl rings from AP.\udMembranes characterization includes degree of sulfonation, ion-exchange capacity, water uptake and\udproton conductivity. TGA–DTA analysis shows that the hybrid membranes are thermally stable up to\ud190 ◦C. Chemical stability of hybrid membrane against sulfonation and doping processes was demonstrated\udby FTIR and UV–vis-NIR. The membranes present a high ion-exchange capacity, similar to the\udNafion®, and water absorptions below 10%. Conductivities around 10−3 S/cm have been obtained at 40 ◦C\udand 65% relative humidity and 3×10−3 S/m at 110 ◦C and 100% RH. These results show that this new kind\udof hybrid membranes possess good mechanical properties, high thermal and oxidative stability and high\udproton conductivity, making them an alternative to be used as electrolytes up to 150 ◦C in PEM fuel cells\udas well as for lower temperatures and humidity (40 ◦C, 65% RH).