High-performance and stable poly(carbazole)-based anion exchange membrane containing rigid-flexible coupled side-chains for fuel cells

Abstract

A series of novel poly(carbazole)-based copolymers tethered with three different cationic groups at the bottom of rigid-flexible coupled side-chains is prepared via superacid-catalyzed polymerization and developed as anion exchange membrane (AEM) for fuel cells. It aims to improve conductivity by aggregating long alkyl chains with good flexibility to make dense cationic groups form large ion transport channels, and the dimensional stability can be improved by the rigid unit due to its large free volume. Meanwhile, the effects of the three cations on the properties of this series of membrane materials are also further investigated. The results show that these AEMs have an ion exchange capacity (IEC) of 2.03–2.21 mequiv. g−1, exhibiting a high ionic conductivity of 133.7–151.3 mS cm−1, which is attributed to the microphase separation structure constructed by the hydrophilic/hydrophobic difference between this unique side-chain and backbone. These AEMs can remain at least 82% ionic conductivity after immersion in 2 M NaOH solution at 80 °C for 1080 h, indicating excellent alkaline stability. Finally, the AEM and binder prepared in this work are applied to a single cell, displaying a maximum power density of 546 mW cm−2 and an excellent durability, which demonstrates a promising application in fuel cells.