Fluoropolymer electrolyte fuel-cell membranes with nano-scale structures controlled by ion beam irradiation

Yamaki, Tetsuya; Kozone, Yuichi; Hiroki, Akihiro; Asano, Masaharu; Kubota, Hitoshi*; Yoshida, Masaru

We prepared polymer electrolyte fuel-cell membranes with controlled nano-scale proton conducting pathways by ion track technology. One of the preparation methods involves (1) the swift heavy ion irradiation of fluoropolymer films (track formation) and subsequent chemical etching to obtain nano-sized cylindrical pores and (2) introduction of sulfonic acid groups into the etched pores. The resulting membranes exhibited anisotropic conductivity in the thickness direction, less water uptake and methanol permeability compared to Nafion.