Degradation-Resistant and High-Ionic-Conductivity Noncoplanar Poly(aryl ether Sulfone) Anion Exchange Membranes Via Cross-linking Strategy for Alkaline Water Electrolyzers

Achieving notable OH– conductivity and high stability of anion exchange membranes (AEMs) simultaneously is crucial for the commercial viability and environmental friendliness of AEM water electrolyzers for hydrogen production; however, this remains a huge challenge. Herein, a range of new fluorene-based macromolecular cross-linked poly(aryl ether sulfone) anion exchange membranes featuring flexible side chains with cations were developed via polycondensation, grafting, and implanting various cross-linking structures (imidazole ring and diamine chain types). Remarkably, the incorporation of imidazolium rings utilizing multicationic cross-linkers resulted in the formation of continuous ion channels for OH– due to the robust π-electron conjugation effect of the imidazolium rings that provided sufficient stability. With an exceptional performance of high OH– conductivity (130.95 mS/cm at 80 °C), the well-engineered Im@G-PAESA AEM also showcased a low swelling ratio (10.09% at 80 °C) and vigorous mechanical strength (41.95 MPa). Impressively, Im@G-PAESA retained a conductivity of 80.86% after prolonged immersion in 1 M NaOH over 1200 h (60 °C). Furthermore, water electrolyzer utilizing Im@G-PAESA-MEA attained a current density of 560.91 mA/cm2 at 2.0 V and remained stable for a period of 72 h. Therefore, AEMs based on multi-imidazole cationic cluster cross-linked poly(aryl ether) exhibited broad practical application prospects in water electrolyzers.