Novel hydroxide conducting sulfonium-based anion exchange membrane for alkaline fuel cell applications

Abstract

Sulfonium-based high performance alkaline polymer electrolyte was successfully synthesized from commercial poly (ether sulfone) by first inducting the chloromethyl groups and thereby functionalization with dimethyl sulfide. Novel anion exchange membranes were obtained by an anion exchange with 1.0 M KOH. Lewis acid (zinc chloride, ZnCl2) catalyzed chloromethylation reaction was performed using chloromethyl methyl ether and thionyl chloride. The prepared tertiary sulfonium functionalized alkaline poly(ether sulfone) membrane exhibited outstanding solubility in polar aprotic solvents; thus, the flexible and tough membranes could be prepared by casting from the DMSO solution. The resulting ionomer membrane showed hydroxide conductivity above 10−2 mS cm−1 at room temperature with the ion exchange capacity value of 1.37 mmol g−1. The chemical structure of the chloromethylated polymer and polymer electrolyte were identified by 1H NMR. The polymer membrane will be characterized by FT-IR, thermogravimetric analysis (TGA), ion exchange capacity (IEC), water uptake and hydroxide conductivity assessment.