A facile route to enhance the properties of polymer electrolyte-based organic-inorganic hybrid proton exchange membranes

A series of novel sulfonated polyimide (SPI)-mesoporous organosilicate (MSiSQ) hybrid proton exchange membranes (PEMs) with enhanced properties were prepared by in situ sol-gel process. The MSiSQ was synthesized from 3-isocyanatopropyltriethoxysilane (IPTES) and 8-hydroxyquinoline-5-sulfonic acid (SQ). The microstructure and properties of the hybrid membranes were characterized. The microstructure of the membranes can be regulated by the hydrogen bonds formed by the nitrogen atoms of MSiSQ phase and the hydrogen atoms of sulfonic acid groups in SPI. The uniform distribution of sulfonate ion clusters was observed in the hybrid membranes. The hybrid membranes exhibited superior performance as compared with that of pure SPI membrane such as the proton conductivity, methanol permeability, mechanical properties and thermal stabilities. The SPI-40-MSiSQ membrane showed a maximum proton conductivity of 0.566 S cm− 1 at 80 °C and 100% relative humidity, an optimal selectivity of 12.8 × 106 S s cm− 3 and an improved fuel cell performance as compared with pure SPI membranes. These excellent properties could be attributed to the formation of the continuous microstructure and well-connected proton transport channels due to the strong hydrogen bonding interaction and the mesoporous structure in the hybrid membranes.