SPEES/PEI-based highly selective polymer electrolyte membranes for DMFC application

Abstract

Polymer composite membranes based on sulfonat- ed poly(phenylene ether ether sulfone) (SPEES) membrane with varying concentrations of poly(ether imide) (PEI) were prepared. The sulfonation of PEES was carried out with con- centrated sulfuric acid at 10 °C, and the sulfonation degree was maintained as 70 %. The introduction of PEI into the hydrophilic SPEES matrix provided good chemical stability to the membrane. The water uptake, ion exchange capacity, and proton conductivity decrease with increasing PEI content. Scanning electron microscopy (SEM) indicates that PEI par- ticles are homogeneously dispersed into the composite mem- brane. Thermogravimetric analysis (TGA) showed that all the composite membranes exhibited good thermal stability. On the other hand, the methanol permeability of the composite membranes gradually decreases from 4.23 × 10 �7 cm 2 s �1 to 8.84 × 10 �8 cm 2 s �1 , which is lower than that of the Nafion 117 membrane. The relative selectivity of the PEI-incorporat- ed SPEES membranes was higher than that of the Nafion membranes. From the observed results, the prepared SPEES/ PEI-15 composite membrane can be considered as apposite polymer electrolyte membranes for the application of direct methanol fuel cells (DMFCs).