Development of nano-structure controlled polymer electrolyte fuel-cell membranes using high-energy heavy-ion beams; Irradiating-ion dependence of their proton conductivity

Yamaki, Tetsuya; Sekine, Toshihiko*; Sawada, Shinichi; Koshikawa, Hiroshi; Suzuki, Akihiro*; Terai, Takayuki*; Asano, Masaharu; Maekawa, Yasunari

My presentation deals with the application of high-energy heavy ion beams from the cyclotron accelerator of Takasaki Ion Accelerators for Advanced Radiation Application (TIARA), JAEA. Our strategic focus is centered on using nano-scale controllability of the ion-beam processing; the membrane preparation involves (1) the irradiation of commercially-available base polymer films with 56 MeV N, 150 MeV Ar, and 450 MeV Xe beams, (2) graft polymerization of a styrene monomer into electronically-excited parts along the ion trajectory, called latent tracks, and (3) sulfonation of the graft polymers. Interestingly, the resulting membranes exhibited the proton conductivities which were largely dependent on the track structures of the bombarding particles. This finding can be rationalized by considering the local density of the proton-conductive sulfonic-acid groups introduced in the membranes.