Development of polymer electrolyte fuel-cell membranes by ion beam applications

We have been recently developing polymer electrolyte membranes for fuel cells by high-energy ion beam applications. One of the preparation methods for these so-called 'nano-scale structure-controlled membranes' involves (1) the swift heavy ion irradiation of fluoropolymer films and subsequent chemical etching to obtain nano-sized cylindrical pores and (2) introduction of proton-conducting groups into the etched pores. The pore size of a polyvinylidene fluoride (PVDF) track-etched membrane was controlled by adjusting the irradiation parameters as well as etching conditions such as the concentration and temperature of the alkaline solution and time. The surface observation using scanning electron microscopy confirmed the filling of polystyrene chains into the etched pores by graft polymerization based on a γ-ray pre-irradiation technique. The graft chains were sulfonated to provide ion exchange membranes with proton conductivity only in the thickness direction. (author)