Anion exchange membrane with enhanced alkaline stability through radiation grafting of ETFE for solid polymer electrolytes

Abstract

Solid polymer electrolyte membranes are considered as the nub of many electrochemical devices. Given the climate crisis and related concerns, the evolution of new membrane materials to support the sustainable systems is inevitable. Building on recent advances with the radiation technique and polymer chemistry, herein, anion exchange membranes (AEMs), ETFE‐g‐1VIm/4VP, were fabricated through graft copolymerization of vinyl heterocyclic monomer binary mixture, such as 1‐vinylimidazole (1‐VIm) and 4‐vinylpyridine (4‐VP) onto ethylene tetrafluoroethylene (ETFE), a main polymer backbone without aryl ether bonds. The grafting reaction was achieved at 60°C and then followed by quaternization as a subsequent step. The effects of various reaction grafting conditions were investigated. The ETFE‐g‐1VIm/4VP AEM were characterized w.r.t the morphological and structural features. The dense surface of the grafted membranes is proved by field emission‐scanning electron microscopy (FE‐SEM) images, which also show that the vinyl entities are clearly distributed in the prepolymer, which may lead to a continuous ion transport channel. AEMs processed from the highest graft yield showed good hydroxide conductivity at 90°C, reaching 16.9 mS/cm due to the presence of more transport sites. The same membrane has a relatively good alkaline stability, which is studied through weight percentage method and FT‐IR. Hence, we assume that the introduction of multi‐cationic moieties, pyridinium and imidazolium, contributes to the performance of anion exchange membranes and makes a perfect balance, especially the hydrophilicity and hydrophobicity. These data highlight the potential of the copolymer as an anion exchange membrane for wide spectra of electrochemical applications.Highlights AEMs based on ETFE‐g‐1VIm/4VP are developed via radiation grafting. The membrane exhibits remarkable alkaline stability. FT‐IR, SEM, and weight percentage methods were used to prove the alkaline stability. The membrane has the potential to be used for different electrochemical applications.