Simple and Effective Cross-Linking Technology for the Preparation of Cross-Linked Membranes Composed of Highly Sulfonated Poly(ether ether ketone) and Poly(arylene ether sulfone) for Fuel Cell Applications

Cross-linking technology has been considered as one of the effective strategies for improving the physicochemical stability of proton-exchange membranes (PEMs) for fuel cell applications. However, the complicated procedure, which consists of various reagents and multiple steps to form the proton-conducting cross-linked membranes, has been known to be disadvantageous to increasing the application of the cross-linking method. In this study, we present a simple and effective cross-linking technology for the development of high-performance cross-linked PEMs without any tedious chemical processes and catalysts or additives. A series of cross-linked membranes could be prepared by a simple one-step stage of casting and heating the mixture of sulfonated poly(ether ether ketone) (SPEEK) and sulfonated poly(arylene ether sulfone) (SPAES) in dimethyl sulfoxide (DMSO) solution, where DMSO works as the solvent and the reagent at the same time without any tedious chemical reaction steps. By controlling the cross-linking density, cross-linked membranes having tunable physicochemical stabilities and mechanical properties with outstanding proton conductivity could be obtained. The fuel cell performance of the membrane electrode assembly employing the cross-linked membrane with the optimum cross-linking density and composition ratio showed a maximum power density of 0.70 W cm–2, which was superior to that employing Nafion 212 (0.58 W cm–2) at 80 °C under fully humidified H2/air condition.