Highly conductive alkoxy chain cross-linked poly (aryl piperidinium) anion exchange membrane for water electrolysis

Cross-linking represents a trenchant approach to coordinating the "trade-off" effect between ion conductivity and dimensional stability. Still, it is limited by the brittleness of materials caused by hydrophobic crosslinkers. We hereby introduced a hydrophilic alkoxy chain crosslinker containing dipolar molecules. The highly flexible C-O-C chain in the crosslinker allows for the formation of the hydrogen bond network, which amplifies the cation self-aggregation ability through Cation-Dipole interaction and constructs rational hydrophilic/hydrophobic microphase separation structures to establish a long-range ordered OH– pathway. Meanwhile, flexible crosslinkers suppressed swelling and enhanced flexibility. Among the alkoxy chain cross-linked poly (p-terphenyl piperidinium), QPTP-IEO15 exhibited the optimal OH– conductivity of 148.5 mS cm−1 at 80℃. Moreover, the QPTP-IEO15 membrane demonstrated remarkable alkaline stability while maintaining a low swelling ratio (15.0 % at 80℃) and adequate mechanical strength: ion conductivity and ion exchange capacity only deteriorated by 3.3 % and 2.9 % after soaking in a 1 M KOH solution (80℃) for 1200 h, respectively. Additionally, Anion exchange membrane water electrolysis based on QPTP-IEO15-MEA achieved a current density of 1800 mA cm−2 at 3.11 V.