Synthesis and properties of anion exchange membranes with dense multi-cations and flexible side chains for water electrolysis

To further improve the performance of anion exchange membranes (AEMs) for water electrolysis , a class of poly (aryl ether sulfone)s with multiple quaternary ammonium cations on the side chains (PAES-MQA-x, “x” represents a functional chain segments, “MQA” represents multiple quaternary ammonium) are designed and synthesized. Their chemical and micro phase separation structures are characterized by hydrogen nuclear magnetic resonance ( 1 H NMR) and atomic force microscope (AFM), respectively. The ion exchange capacity of PAES-MQA-x is in the range of 2.01–2.51 mmol/g. Their water uptake, swelling ratio and ionic conductivity at 80 °C are in the range of 32.7–63.2%, 12.9–18.6% and 106.23–140.85 mS/cm, respectively. The retention ratio of ionic conductivity for PAES-MQA-0.18 is up to 72.5% after immersing in 2 M NaOH solution at 80 °C for 480 h. The current density of the electrolyzer with PAES-MQA-0.18 at 2.0 V is up to 1121.5 mA/cm 2 measured in 2 M NaOH solution (cathode catalyst: Pt/C; anodic catalyst: IrO 2 ), and the electrolyzer also has good operation stability when the current density is 500 mA/cm 2 . Meanwhile, a comparative investigation is conducted on the relationship between the structure and properties of these membranes and some reported AEMs.