In this study, a series of composite membranes for Proton Exchange Membrane Fuel Cell (PEMFC) were synthesized. PEMFCs are of much interest nowadays because of the features such as ease in setting up and low temperature operation. Various properties of the composite membranes like ion exchange capacity, durability, tensile strength, percentage elongation, and methanol permeability were studied. The thermal stability of the membrane was analyzed using Thermogravimetric Analysis (TGA) technique. The structural characterization was done by Fourier Transform Infrared (FT-IR) method. The X-ray Diffraction (XRD) analysis gave information about the crystallinity of the composite. Methanol permeability was found to be decreasing with increase in the content of SWA, but durability was decreasing. The mechanical properties were studied using universal testing machine. Both the tensile property as well as percentage elongation decreased with increase in the content of Silicotungstic Acid (SWA). The Dynamic Mechanical Analysis (DMA) was carried out to determine the T_g of the composite. The conductivity values were determined by impedance spectroscopy. Durability was studied using Fenton's reagent.

Fuel cells have attracted much attention over the last decade as portable devices for energy generation and as replacement for batteries. Fuel cells can best be defined as excellent electrochemical energy converters that combine a fuel (normally hydrogen, methanol, etc.) and an oxidant (usually oxygen, air, etc.) and convert a fraction of their chemical energy into useful electric energy (Schauer et al., 2001). It is known that up to a certain level of higher degree of sulfonation of the polymer, higher Relative Humidity (RH) and higher temperature, the conductivity of the polymer can be improved (Benavente et al., 2000; Alberti et al., 2001; Freire and Gonzalez, 2001; and Kreuer, 2001). Similar is the case for some pure inorganic materials (Casciola, 1989; and Alberti et al., 2001) and for composites when formed (Bonnet et al., 2000; Park et al., 2000; Alberti et al., 2001; and Jones and Roziere, 2001) .

The crystalline forms of Phosphotungstic Acid (PWA) and phosphomolybdic acid (two compounds of the family of heteropoly acids) containing the maximum number of water molecules in their reticular structures exhibit good proton conductivity (Nakamura et al., 1979). However, they are very sensitive to the surrounding conditions like relative humidity and temperature, which can modify the crystalline structure of these heteropoly acids or transform them into solution (Nakamura et al., 1981 and 1982). These factors make it difficult to manage these materials as solid electrolytes with stable crystalline structure in technological devices like fuel cells, where water is produced during operation. Focusing the attention on the more studied PWA, it is known that this material exists in different crystalline structures, each having a different number of water molecules (Staiti and Minutoli , 2001). The crystalline structure with 29 water molecules gives the highest proton conductivity. The utilization of heteropoly acid as the concentrated solution is also of great interest, because of its high proton conducting ability (Staiti et al., 1998). The results of experiments with fuel cells working with PWA in solid or concentrated solution form exhibit interesting electrochemical performance (Staiti et al., 1997 and 1998).

Sulfonated Poly Ether Ether Ketone, Silicotungstic Acid, Sulfonated poly ether ether ketone, Silicotungstic acid, Thermogravimetric Analysis, TGA, X-ray Diffraction, XRD, Fourier Transform Infrared, FT-IR, Silicotungstic Acid, SWA, Dynamic Mechanical Analysis, DMA, Relative Humidity, RH, Proton Exchange Membrane Fuel Cell, PEMFC.