Effect of Filler Content on Transport Properties of Sulfonated Polyether Ether Ketone (SPEEK) Composite Proton Exchange Membranes

Proton exchange membrane for direct methanol fuel cell was developed by the incorporation of silicotungstic acid supported on silica (SiO2-SiWA) into SPEEK polymer. The properties of composite membranes with various silica/SiWA ratios were investigated and compared in this study. It was found that high silica to SiWA weight ratio (2:1) resulted in porous membrane with high proton conductivity and moderate methanol permeability. Reduction in the aforementioned ratio to 1:1 resulted in a more compact structure with better thermal stability, however, leaching of SiWA from the membrane occurred due to insufficient support. SPEEK membrane incorporated with 10 wt% SiO2 and 5 wt% SiWA showed the highest selectivity of 6.44 x 10(4) S.s/cm(3) and performed better than that of the pure SPEEK membrane. These results suggested that these membranes have potential to be considered for DMFCs applications.