Proton conducting organic-inorganic composite membranes under anhydrous conditions synthesized from tetraethoxysilane/methyltriethoxysilane/trimethyl phosphate and 1-butyl-3 methylimidazolium tetrafluoroborate

Anhydrous proton conducting organic-inorganic hybrid membranes were fabricated by sol-gel process with tetraethoxysilane/methyltriethoxysilane/trimethyl phosphate and 1-butyl-3 methylimidazolium tetrafluoroborate (BMIMBF(4)) ionic liquid as precursors. Chemical stability of these hybrid membranes was investigated by Fourier transform infrared spectroscopy and (31)P, (1)H, and (13)C magic angle spinning nuclear magnetic resonance measurements. Thermogravimetric analysis and differential thermal analysis measurements confirmed that the hybrid membranes were thermally stable up to 280 degrees C. The effect of ionic liquid addition on the microstructure of the hybrid membranes was examined by Scanning electron microscopy and Energy dispersive X-ray analysis micrographs and no phase separation was observed at the surfaces of the composite membranes and also homogeneous distribution of all the elements was confirmed. For all the prepared composite membranes the conductivities were measured within the temperature range (-30)-150 degrees C, and a maximum conductivity of 6.74 x 10(-3) S/cm at 150 degrees C was achieved for 40 wt.% ionic liquid based hybrid membrane, under non-humidified conditions. The hydrogen permeability values were decreased with the temperature increment from 20 degrees C to 150 degrees C and the measured H(2) permeability value for 40 wt.% ionic liquid based hybrid membrane was 0.5 x 10(-12) mol/cm s Pa at 150 degrees C. For 40 wt.% [BMIMBF(4)] doped hybrid membrane, membrane electrode assemblies were prepared and a maximum power density value of 2 mW/cm(2) at 4.73 mA/cm(2) as well as a current density of 7.4 mA/cm(2) was obtained at 150 degrees C under non-humidified conditions when utilized in a H(2)/O(2) fuel cell. (C) 2010 Elsevier B.V. All rights reserved.