Development of nanostructure-controlled fuel-cell membranes by ion irradiation technique

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

To realize mass commercialization of fuel cell, many kinds of properties, such as high proton conductivity, low water swelling and high mechanical strength, are required for a polymer electrolyte membrane. Utilizing nano-scale controllability of an ion beam is our strategic way for the preparation of fuel-cell electrolyte membranes. The preparation of membranes involve (1) the irradiation of heavy ions with different masses and energies; (2) the grafting of styrene into electronically-excited region along the ion trajectory called the latent track; (3) sulfonation of the graft chains. According to the FE-SEM and TEM observations, the proton conductive electrolyte part appeared to extend through the membrane thickness with dimensions of tens-to-hundreds nanometers, which agreed with the calculated latent track diameter. Correlations between membrane properties, such as proton conductivity and nanostructure were investigated.