In Situ Formation of Triazine-Branched Poly(Aryl Piperidinium) Anion Exchange Membranes for High-Performance Water Electrolyzers

Abstract

In the technological development of anion exchange membrane water electrolyzers (AEMWEs), it is crucial to produce anion exchange membranes (AEMs) that exhibit high ion conductivity, sufficient alkaline durability, and excellent mechanical robustness. This study successfully develops high-performing triazine-branched poly(aryl piperidinium) AEMs by a killing-two-birds-with-one-stone strategy, in which both the generation of triazine-branched structures and the polycondensation reaction to generate the backbones of branched poly(aryl piperidinium) AEMs are achieved under the same trifluoromethanesulfonic acid (TFSA)-catalyzed reaction system. The obtained AEMs with an appropriate degree of triazine branching display the formation of larger free volumes and significantly promoted microphase separation, effectively enhancing ion conductivity while reducing the swelling ratio. Specifically, the QPTPB-10 AEM exhibits an OH^– conductivity of 175.0 mS cm^–1, a swelling ratio of 19.3%, and a water uptake of 132.9% at 80 °C. Moreover, it also displays outstanding alkaline durability and maintains 90.6% of cationic groups after soaking in 3 M NaOH at 80 °C for 1500 h. The related AEMWE cell possesses an outstanding current density of 1.62 A cm^–2 at 2 V in 1 M KOH (80 °C), along with stable working for 1000 h at a constant current of 0.5 A cm^–2. Consequently, the as-obtained AEMs have a huge potential for application in the field of AEMWEs. It is expected that this killing-two-birds-with-one-stone strategy may offer more possibilities in terms of expanding the topological structure of AEMs.