High‐Performance Quaternized Polybenzimidazole Anion Exchange Membranes With Quaternary Ammonium Cationic Group Covalent Organic Framework/Graphene Oxide Hybrid Fillers

ABSTRACT Anion‐exchange membranes (AEMs) are widely studied as key components of anion‐exchange membrane water electrolyzers (AEMWEs) and anion‐exchange membrane fuel cells (AEMFCs). Polybenzimidazole (PBI) is a commonly used material for AEMs. Here, we propose a composite approach involving the stepwise quaternization modification of PBI molecular chains and introduction of a covalent organic framework (COF, TpTG Cl ) along with two‐dimensional rigid graphene oxide (GO) nanoparticles. This strategy aims to address the significant “trade‐off” effect between hydroxide conductivity and dimensional stability. This approach uses a simple two‐step method to prepare quaternary ammonium‐modified PBI (QPBI), enhancing terminal cation mobility to facilitate the aggregation into ionic clusters, thereby improving the hydroxide ion transport ability of the AEM. The mechanical properties and dimensional stability of the composite membranes are significantly enhanced under the synergistic effect of TpTG Cl and GO. The prepared QPBI/GO/TpTG Cl composite membranes exhibit a fracture strength generally above 50.0 MPa in the wet state, the conductivity exceeding 70.0 mS cm −1 at 80°C, and the swelling rate is reduced by approximately 23.7% compared to the QPBI/TpTG Cl 1wt% composite membrane. Among them, the QPBI/GO 1wt% /TpTG Cl 1wt% composite membrane shows a current density of 382 mA cm −2 at 2.5 V, which is 24.0% higher than that of the QPBI membrane.