Sulfonated poly(phenylene sulfide) grafted polysulfone proton exchange membrane with improved stability

Low oxidation stability is one of the key issues hindering practical application of non-fluorinated proton exchange membrane in fuel cells. As a part of the efforts to address this issue, we herein report a novel hydrocarbon proton exchange membrane of polysulfone (PSf) grafted with sulfonated poly(phenylene sulfide) (sPPS). The proton conductivity , thermal and oxidation stability of the PSf-g-sPPS membranes were studied and compared against those of conventional polysulfone-graft-sulfonated polystyrene (PSf-g-sPS) membranes. The PSf-g-sPPS membranes exhibited superior chemical stability relative to those of PSf-g-sPS membranes: the mass retention ratio of former is 10% higher than that of latter after treatment in Fenton's reagent. Additionally, the conductivity retention ratio of PSf-g-sPPS membranes at 23% graft degree is ca. 30% higher than those of PSf-g-sPS membranes. In terms of thermal stability, the PSf-g-sPPS complete degradation temperature is higher than PSf-g-sPS complete degradation. Based on our study, grafting of aromatic side chain is effective to improve the oxidation stability of non-fluorinated PEM while maintaining good conductivity and swelling resistance.