Structural study on inorganic/organic hybrid composite membranes

Abstract

New composite materials consisting of phosphosilicate (P₂O₅-SiO₂), phosphotungstic acid (PWA), 3-mercaptopropyltrimethoxysilane (MPTS) and glutaraldehyde (GL) were prepared, and a high proton conductivity of 10⁻² S cm⁻¹ was observed at room temperature. By incorporating 3-mercaptopropyltrimethoxysilane (MPTS) and glutaraldehyde (GL) in to the P₂O₅-SiO₂-PWA inorganic matrix, the composites showed high proton conductivity in the range of 10⁻²–10⁻¹ S cm⁻¹ at 120 °C. The structural formation was confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and morphological analysis. The thermal properties were investigated by thermogravimetry (TG) and differential thermal analysis (DTA). A new inorganic–organic composite membrane was successfully prepared by a sol–gel process through hydrolysis and condensation of MPTS and tetraethoxysilane (TEOS). These P₂O₅-SiO₂-PWA-MPTS, P₂O₅-SiO₂-PWA-GL and P₂O₅-SiO₂-PWA-MPTS-GL hybrid composite membranes showed high proton conductivities as a function of temperature. Moreover, they were thermally stable in air up to 250 and 300 °C due to the presence of a tolerant inorganic SiO₂ framework in the matrix.