Nano-Structure Controlled Polymer Electrolyte Membranes for Fuel Cell Applications Prepared by Ion Beam Irradiation

Abstract

Fluoropolymer-based electrolyte membranes for fuel cells were prepared by using heavy ion beams from the cyclotron accelerator of the Takasaki Ion Accelerators for Advanced Radiation Application (TIARA), Japan Atomic Energy Agency (JAEA). The preparation method for these so-called nano-scale structure-controlled membranes involves (i) the swift heavy ion irradiation of polyvinylidene fluoride (PVDF) films and subsequent chemical etching to obtain cylindrical pores with a diameter of 100 nm, and (ii) the filling of proton-conducting polymer chains into the etched pores by gamma-ray-induced graft polymerization. The proton transport only in the thickness direction was observed for the resulting membranes with controlled ion exchange capacities, indicating the formation of one-dimensional straight proton-conducting pathways parallel to the ion-beam incident axis. The membranes exhibited a lower water uptake and reduced methanol permeability compared to commercially-available Nafion probably due to the restricted structures.