Cross-linker effect in ETFE-Based radiation-grafted proton-conducting membranes I. Properties and fuel cell performance characteristics

Abstract

Cross-linking of styrene grafted and sulfonated fuel cell membranes is essential to obtain well-performing and durable membranes. In this study, the properties and fuel cell performance of radiation grafted membranes based on poly(ethylene-althexafluoropropylene)(ETFE) 25 micron with different extent of cross-linking, using divinylbenzene (DVB )monomer to styrene, were investigated. The water uptake and proton conductivity decrease as a function of increasing the extent of crosslinking. Also, the membranes become more brittle. Fuel cell performance is limited by the high ohmic resistance of the membrane at high degrees of cross-linking, whereas at low degrees of cross-linking the membrane–electrode interface is of poor quality. Optimum performance is obtained at an extent of cross-linking corresponding to a styrene:DVB monomer ratio v/v of 95:5 in the grafting solution.