A Comparative Study on Sulfonated PEEK and PVDF Blend Membranes for Direct Methanol Fuel Cells

Abstract

Various polymeric blend membranes based on sulfonated poly(ether ether ketone) (sPEEK) and poly(vinylidene fluoride) (PVDF) are prepared by solution casting method for direct methanol fuel cells (DMFCs). Physicochemical properties of the membranes are studied after blending sPEEK with PVDF in different ratios. It is found that the thermal stabilities of all blend membranes are above 200^oC which is sufficiently high for use in DMFC. Water uptake values of the blend membranes vary between 9-20% as a function of the blend composition. Similar to the water uptake property, proton conductivity values and surface hydrophilicity of the samples increase with sPEEK portion in the blend. Water uptake of sPEEK30/PVDF70 blend membrane is about 9.2%, the proton conductivity of this membrane is 0.8 mS.cm^-1, and the methanol permeability of sPEEK30/PVDF70 blend membrane is about 1/10 that of untreated Nafion^®117 reported in the literature. Based on the results, it is concluded that the sPEEK/PVDF polymer blends can be considered as a candidate membrane for DMFC applications considering their controllable properties, cheapness and easy preparation.