Bis-cationic crosslinked anion exchange membranes based on carbazole-containing polyaromatics with excellent ionic conductivity for alkaline water electrolysis

As the core component in anion exchange membrane water electrolyser (AEMWE), anion exchange membrane (AEM) directly determines the electrolysis performance and long-term durability of AEMWE. Herein, we synthesized novel poly(carbazole-p-terphenylpiperidine) (PCTP-x) copolymers and then prepared a series of biscationic cross-linked AEMs (QPCTP-x-bpip) using the Menshutkin reaction between the cross-linker 4,4 '-trimethylenebis(1-methylpiperidine) and the alkyl bromide on the polymer side chains. For comparison, noncrosslinked AEMs containing alkylpiperidinium side chains (QPCTP-x-pip) were prepared via a grafting reaction of alkyl bromide with 1-methylpiperidine. The bis-cationic crosslinked membrane exhibited high hydroxide conductivity of 190.0 mS cm- 1, and demonstrated outstanding alkaline stability in a 1 M KOH solution at 80 degrees C, retaining more than 90 % of the initial hydroxide conductivity and tensile strength after 2200 h alkaline treatment. Meanwhile, the flexural carbazole backbone enhanced polymer solubility, enabling the utilization of QPCTP-20-pip as an anion exchange ionomer (AEI) in AEMWE. For the water electrolysis testing, AEMWE employing QPCTP-20-bpip as the AEM and QPCTP-20-pip as the AEI exhibited excellent performance, achieving a current density of 2910 mA cm- 2 at 2.0 V using a 1 M KOH feed at 80 degrees C. Moreover, the voltage increase during the in-situ durability test over 200 h was a mere 0.65 mV/h, demonstrating its promising potential for AEMWE applications.