Highly Conductive and Low Swelling of Fluorine-Free Poly(carbazolyl aryl piperidinium) Anion Exchange Membrane for Water Electrolyzer

The absence of anion exchange membranes (AEMs) that concurrently exhibit high hydroxide conductivity and superior dimensional stability poses a major challenge for the advancement of a high-performance AEM-based water electrolysis system. Herein, a series of block-cross-linked poly(aryl piperidinium) AEMs were prepared via superacid polycondensation, nucleophilic substitution, and the Menshutkin reaction. The molecular configuration of poly(aryl piperidinium) was manipulated by introduction of backbone rigidity, steric hindrance, and microphase-separated structures, thus realizing the design of distinct polymer network architectures for the AEM electrolysis application. It was found that the presence of nonrotatable carbazole molecules, which enlarged the molecular space within the polymer, contributed to the distinct hydrophilic–hydrophobic microphase separation structure. Moreover, the dual “block-cross-linking” strategy not only improved the structural stability of the polymer but also optimized its ion transport properties. Notably, AEMs featuring N-ethyl carbazole structure in their backbone exhibited remarkable dimensional stability (swelling ratio of 10 %, water uptake of 17.39 %), high mechanical stability (tensile strength of 43.12 MPa), and high conductivity of 113.55 mS cm –1 . Furthermore, the practical application of c-QPCTP AEMs in AEMWEs was demonstrated, achieving a current density of 607 mA cm –2 at a constant voltage of 1.6 V. In addition, the AEMs can be maintained in stable operation for 66 h at a constant current density of 250 mA cm –2 . Therefore, the chemical design in this work provides an alternative pathway to balance the dimensional stability and OH – conductivity of AEMs in the application of AEM-based electrolysis.