A Study On The Sulfonated Polymer/heteropoly Acids Composite Membranes

Direct methanol fuel cells(DMFC) have attranted considerable attention as an alternative to the present power sources, since they offer numerous benefits, including high efficiency, high power density, low or zero emissions and easy fuel carriage. As the most widely used membrane in the fuel cells, the high cost and crossover of methanol through the Nafion membrane restrict the commercialization of DMFC.In order to lower the cost of the membranes and the crossover of methanol, sulfonated polysulfone(SPSF) membranes and sulfonated poly(phthalazinone ether solfone ketone)(SPPESK) membranes with various degree of sulfonation(DS) were prepared. Methanol permeability of these membranes is about 10^-7～10^-8 cm² /s, the conductivity of the membranes is lower than that of Nafion membrane.Heteropoly acids(HPAs) with high thermal stability are known to be the most conductive solids among the inorganic solid electrolytes. Worrying about the nature of the HPAs water-soluble, they can't be made to a self-supporting membrane. As the proton acids, HPAs can be used to prepare inorganic-organic composite membranes. Heteropoly acid anions of Keggin structure which are the most fabricated easily and stable of all yields the highest proton conductivity. PWA and SiWA are choosed to prepare the composite membranes because of their Keggin structure Heteropoly acid anions.FT-IR,XRD,SEM measurements of the composite membranes show that PWA and SiWA are well dispersed in the membranes. The Proton conductivity and permeability of the composite membranes are higher when the content of PWA/SiWA is higher. Methanol permerbility of these membranes which is up to the requirement is about 10^-7～10^-8 cm²/s. The test results show that the Proton conductivity and permerbility of SiWA/SPPESK composite membranes is lower than that of PWA/SPPESK composite membranesmethanol.