Free volume study of sulfonated FEP proton exchange membrane

Oka, Toshitaka   ; Oshima, Akihiro*; Washio, Masakazu*

The polymer electrolyte fuel cell (PEFC) is a promising electrochemical device to produce power through hydrogen and oxygen reaction. It has been expected as a leading future clean power source for a vehicle and a residential power generation. Proton exchange membrane (PEM) is a key material for the performance and the cost of PEFC, development of a high performance and a low-cost PEM is required. Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) was irradiated by an electron beam under oxygen-free atmosphere at 25C, grafted with styrene in liquid phase at 80, and then sulfonated with a mixture of chlorosulfonic acid in carbon-tetrachloride at 25 for 24 h. The free volume size and the o-Ps annihilation probability were affected by not only the amount of the grafted styrene but also the sulfonic acid group.