Inorganic–organic hybrid membranes prepared from 3-aminopropyltriethoxysilane and sulfuric acid as anhydrous proton conductors

We have prepared novel proton conducting inorganic–organic hybrid membranes from 3-aminopropyltriethoxysilane (APTES) and H2SO4 by the sol–gel method. The resulting poly(3-aminopropylsilsesquioxane sulfate or hydrogensulfate) (PAPS-SO4/-HSO4) membranes were thermally stable up to 300 °C. From the results of IR spectra, it was confirmed that sulfuric acids in the membranes react with amino groups of PAPS to form ion complexes. XRD patterns of the PAPS-SO4/-HSO4 membranes showed diffraction peaks assigned to hexagonal structure, which is probably formed by stacking of rodlike polysiloxanes with the ion complexes extruded outside. The PAPS-SO4/-HSO4 membranes with a molar ratio of H2SO4/APTES = 1.0 showed high proton conductivities of 2 × 10− 3 S cm− 1 at 200 °C under dry condition.