Influence of Multiarmed Cores on the Performance of Branched Poly(aryl piperidinium)-Based Anion Exchange Membranes for Water Electrolysis

While incorporating branched architectures is recognized as an effective strategy for enhancing the performance of poly(aryl piperidinium)-based anion exchange membranes (AEMs), systematic studies into how multiarmed cores influence performance remain inadequate. Herein, we report the construction of a series of branched poly(aryl piperidinium) AEMs from multiarmed (1,3,5-triphenylbenzene, tetraphenylmethane, and 9,9-diphenylfluorene) cores and a systematic evaluation of how they affect membrane properties, including free volume, water uptake, swelling ratio, ionic conductivity, and alkaline stability. Four-armed cores were found to yield higher fractional free volumes and specific surface areas than their three-armed counterparts. Moreover, membranes based on 9,9-diphenylfluorene exhibited superior performance, which is attributable to their hybrid rigid–flexible branching structures. Specifically, the optimized QPTPip-DPF-10 membrane delivered an exceptional ionic conductivity of 181.4 mS cm –1 and retained 84.6% of its ionic conductivity after 1080 h in 2 M NaOH at 80 °C. A current density of 2113.2 mA cm –2 was attained at 2.0 V and 80 °C, along with stable operation for more than 720 h at 500 mA cm –2 when used in an AEM water electrolyzer. This study highlights the critical importance of branched-core selection and provides molecular-level design guidelines for advanced AEMs.