Polycarbazole-SEBS-crosslinked AEMs based on two spacer polymers for high-performance AEMWE

Abstract

Poly(aryl piperidinium) (PAP)-based anion exchange membranes (AEMs) are central to recent research due to their high ionic conductivity and chemical stability. PAP-AEM-based water electrolysis (AEMWE) systems exhibit remarkable cell performance. However, the absence of flexible structural units in PAP-based polymers produces brittle membranes, which have degraded mechanical properties. Well-developed ion channels do not form in PAP-based polymers due to the low flexibility of the main chain-type ion-conducting group. The present study aims to fabricate polycarbazole–SEBS-based crosslinked membranes (x-Car-SEBSs) with well-developed ion channels due to the highly flexible spacer-type ion conducting groups by crosslinking two spacer-type polymers, polycarbazole and SEBS, as novel AEM materials. The resulting x-Car-SEBS membranes also exhibit good mechanical properties (tensile strength of 17.2–22.3 MPa and elongation at break between 109.6% and 138.3%), driven by crosslinking SEBS, an elastic polymer component, with polycarbazole, a spacer-type PAP-based rigid polymer. The 40x-Car-SEBS membrane, with a 40% crosslinking degree, shows the most pronounced phase separation and achieves the highest ionic conductivity (153.16 mS cm⁻¹ at 80 °C) and 840 hours of alkaline stability. Furthermore, 40x-Car-SEBS demonstrates superior AEMWE single-cell performance, achieving 1.25 mA cm⁻² at 1.8 V, almost double that of FAA-3-50, a commercial membrane, and higher than previously developed main chain-type crosslinked AEMs and main chain–spacer-type crosslinked AEMs. Moreover, this membrane exhibits excellent cell durability, with a minimal voltage increase of 0.1 V after 100 hours.