Development of nano-structure controlled polymer electrolyte fuel-cell membranes by high-energy heavy ion irradiation

Yamaki, Tetsuya; Kobayashi, Misaki*; Asano, Masaharu; Nomura, Kumiko*; Takagi, Shigeharu*; Maekawa, Yasunari; Yoshida, Masaru*

Our presentation deals with the application of high-energy heavy ion beams to the preparation of nano-structure controlled electrolyte membranes. The membrane preparation involves (1) irradiation of commercially-available base polymer films with 100 MeV O, 400 MeV Fe, or 450 MeV Xe, (2) graft polymerization of vinyl monomers into latent tracks, and (3) sulfonation of the graft polymers. The resulting membranes exhibited anisotropic proton transport, i.e., higher conductivity in the through-plane direction. According to microscopic observations, this is probably because the nearly columnar electrolyte phase with a width of tens-to-hundreds nanometers extended through the membrane. Interestingly, our ion irradiation technique would be able to control the nano-structure of proton-conducting pathways in the membranes. Other excellent membrane properties should also be due to such a controlled structure.