Proton conductive inorganic–organic hybrid membranes prepared from 3-aminopropyltriethoxysilane and phosphoric acid by the sol–gel method

Proton conductive inorganic–organic hybrid membranes with acid–base pairs have been prepared from 3-aminopropyltriethoxysilane and phosphoric acid by the sol–gel method. The self-standing membranes obtained are represented as poly(3-aminopropylsilsesquioxane)-H3PO4 (PAPS–H3PO4) membranes. Infrared absorption spectra of the PAPS–H3PO4 films showed that amino groups of PAPS were protonated by phosphoric acid, indicating the formation of acid–base pairs. X-ray diffraction patterns of the PAPS–H3PO4 membranes showed diffraction peaks attributed to hexagonal structure, which is probably formed by stacking of rodlike polysiloxane with the acid–base pairs extruded outside. The conductivities of the PAPS–H3PO4 membranes with a molar ratio of H3PO4/APTES = 1.0 was 4 × 10− 4 S cm− 1 at 150 °C under dry condition.