Poly(isatin-co-biphenyl alkylene) anion exchange membranes with fluorinated side chains and pendant cationic groups for water electrolysis

Developing high-performance, durable anion exchange membranes (AEMs) is crucial for the industrial applications of anion exchange membrane water electrolysis (AEMWE). Herein, a series of poly(biphenyl-alkylene) anion exchange membranes featuring fluorinated side chains and pendant quaternary ammonium groups are designed and prepared. The incorporation of hydrophobic fluorinated side chains promotes self-assembly, resulting in an obvious microphase separation structure that improves ionic conductivity and reduces membrane swelling. The developed AEMs achieve a maximum OH‾ conductivity of 124 mS cm⁻¹ and a low swelling ratio of 20.8 % at 80 °C. Additionally, the membranes demonstrate excellent alkaline stability, retaining 90.8 % of their conductivity after 1560 h of immersion in 1 M KOH at 80 °C. When assembled in a water electrolyzer, the AEMs exhibit a high current density of 4.7 A cm⁻² at 2 V (80 °C) and maintain outstanding durability at 0.5 A cm⁻² for over 1000 h, with a low voltage decay rate of 210 μV h⁻¹. These developed AEMs show great potential for practical applications in energy conversion devices.