Novel proton conductive inorganic-organic hybrid films doped with a mixture of phosphotungstic acid and phosphomolybdic acid were prepared by sol-gel process with 3-glycidoxypropyltrimethoxysilane (GPTMS), tetramethoxysilane (TMOS), and phosphoric acid as precursors. These hybrid membranes were studied with respect to their structural, thermal, elastic modulus, proton conductivity, and hydrogen permeability properties. The Fourier transform infrared spectroscopy and
nuclear magnetic resonance measurements have shown good chemical stability and complexation of
H3PO4 with both
PW12O403− and
PMo12O403− Keggin anions in the studied hybrid films. The thermogravimetric analysis and differential thermal analysis measurements confirmed that the membranes were thermally stable up to
350 °C. The thermal stability of the membranes was enhanced by the presence of
SiO2 framework. The effect of mixed heteropoly acid (HPA) concentration on the microstructure of the membranes was studied by scanning electron microscopy, energy dispersive x-ray analysis, and transmission electron microscopy micrographs and no phase separation at the surfaces of the TMOS-GPTMS-
H3PO4-HPA membranes was observed, and also homogeneous distribution of all elements was confirmed, indicating that these membranes are homogeneous at nanoscale. High proton conductivity of
9.8×10−2 S/cm with composition of 20TMOS-50GPTMS-
30H3PO4-3PMA-6PWA
(mol %) was obtained at
130 °C and 90% relative humidity (RH). The hydrogen permeability was found to decrease from
1.12×10−10 to
8.5×10−11 cm2/s in the temperature range of
30–130 °C. For 3PMA/6PWA
(mol %) doped hybrid film, membrane electrode assemblies were prepared and a maximum power density of
68 mW/cm2 at
140 mA/cm2 as well as a current density of
262 mA/cm2 were obtained at
130 °C and 50% RH when utilized in a
H2/O2 fuel cell.
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