Preparation and characterization of polymer blend membranes of sulfonated poly(arylene ether ketone) for direct methanol fuel cell

Abstract

In order to maintain the proton conductivity and to reduce the methanol permeability of the polymer membranes composed of proton conducting component and methanol barrier component were prepared for direct methanol fuel cell. The blend membranes of sulfonated poly(arylene ether ketone) (sPAEK_1) (IEC=1.0 meq/g) /Nafion and the blend membranes of sPAEK_1 (IEC=1.0 meq/g) /sPAEK_3 (IEC=1.7 meq/g) were prepared. sPAEK_1 with low IEC was introduced to reduce the methanol permeability through the membrane. Morphology, mechanical stability, water uptake, dimensional stability, methanol uptake, proton conductivity and methanol permeability of the blend membranes were investigated by SEM, AFM, Instron, AC impedance spectroscopy and permeability measuring instrument. The cross-sections of blend membranes showed phase separated morphologies. The effect of phase-separated morphology on the properties of blend membranes was investigated. sPAEK_1/Nafion blend membranes formed the two later structures with sPAEK_1 rich top layer and Nafion rich bottom layer due to the difference in specific gravity. sPAEK_1/sPAEK_3 blend membranes formed the co-continuous morphology due to the enhanced miscibility between two components. The properties like water uptake, proton conductivity, and methanol permeability of sPAEK_1/Nafion blend membranes showed similar values with sPAEK_1 and properties of sPAEK_1/sPAEK_3 blend membranes (NMP-HT) showed intermediate values of two polymers due to the difference in morphology of the blend membranes. sPAEK_1/sPAEK_3 blend membranes showed relatively high proton conductivity and lowered methanol permeability compared to Nafion. sPAEK_1/sPAEK_3 blend membranes (NMP-HT) could be a competent substitution for Nafion. The effect of solvent type and drying condition on the phase separation and morphology of the blend membranes was investigated and then the transport properties of the blend membranes were discussed.