Cerium ions-coordinated 2D Crown Ether Framework as a Radical Scavenging Filler for PEMFC Membranes

 Hydrocarbon-based proton exchange membranes are promising alternatives to perfluorosulfonic acid membranes for proton exchange membrane fuel cells, but their practical application is often limited by insufficient chemical durability and a trade-off between proton conductivity and dimensional stability. In this study, a multifunctional filler, sulfonated poly(arylene thioether sulfone)-grafted two-dimensional crown ether framework coordinated with cerium ions, was incorporated into a sulfonated poly(arylene ether sulfone) matrix. The crown ether framework enabled effective coordination and dispersion of Ce³⁺ ions, while the grafted sulfonated polymer improved interfacial compatibility and provided additional proton-conducting sites. The resulting SPAES/SATS–C₂O–Ce composite membranes showed improved mechanical toughness, enhanced dimensional stability, and higher water uptake compared with pristine SPAES. In particular, the membrane containing 3 wt% SATS–C₂O–Ce exhibited a well-dispersed morphology, enhanced proton conductivity over a wide relative humidity range, and significantly improved oxidative stability in Fenton’s test compared with pristine SPAES and Ce³⁺-doped SPAES without the crown ether framework. Fuel cell tests further demonstrated superior performance of SPAES/SATS–C₂O–Ce-3.0 compared with commercial Nafion 211 and Nafion 212 under fully humidified conditions. These results suggest that Ce³⁺-coordinated, sulfonated 2D crown ether frameworks are effective multifunctional fillers for developing durable and high-performance hydrocarbon-based proton exchange membranes for PEMFC applications.