Enhanced Performance and Stability of Poly(carbazole)-Based Anion Exchange Membranes via Synergistic Dual Side Chains for Fuel Cell Applications

Anion exchange membranes (AEMs) are crucial components of anion exchange membrane fuel cells (AEMFCs), and the development of highly efficient and stable AEMs is fundamental for advancing the practicality of AEMFCs. In this study, we propose the concept of "combining rigidity and flexibility" to design a series of poly(carbazole)-based AEMs with unique dual side chains. One side chain is a flexible dialkoxy chain, while the other consists of a rigid aromatic structure attached to two flexible alkyl chains. The resulting AEMs exhibit a remarkably high ionic conductivity, ranging from 120.2 to 175.7 mS cm–1 at 80 °C, along with an ion exchange capacity of 1.64–2.19 mequiv g–1. These properties are attributed to significant microphase separation facilitated by the strong interaction between the dual side chains. Furthermore, these AEMs demonstrated excellent alkaline stability. Even after being immersed in NaOH solution for 1080 h, their conductivity remains above 92%. This exceptional stability against hydroxide ions is attributed to the large electrostatic potential of the dialkoxy side chain, as verified by density functional theory calculations. Importantly, when incorporated into a hydrogen–oxygen fuel cell, the AEMs enable the fuel cell to achieve a large power density of 605 mW cm–2 at 70% relative humidity. This remarkable performance underscores their potential application prospects in the field of alkaline fuel cells. As a result, our findings contribute to the ongoing advancement of the AEMFC technology.