Polyimide-based anion exchange membranes with synergistic bifunctional block phase separation for alkaline water electrolysis

Anion exchange membrane water electrolysis (AEMWE) is a key technology for converting renewable electricity into green hydrogen, but its large-scale deployment remains constrained by the performance of anion exchange membranes (AEMs). Traditional AEMs suffer from an inherent trade-off between high conductivity and excessive swelling. Polyimides, which combine excellent mechanical properties, dimensional stability, and structural designability, are promising alternative AEM substrates; however, their application is limited by the susceptibility of imide rings to alkaline degradation. This study proposes a synergistic bifunctional block phase separation strategy, in which a chemically phase-separated structure comprising a trifluoromethyl-based hydrophobic block and a benzimidazole-based hydrophilic block is constructed, and the microphase-separated morphology is optimized by tuning the block ratio. This strategy suppresses imide ring hydrolysis through bifunctional synergy, while bicontinuous microphase separation creates continuous, low-resistance OH − transport channels, thereby decoupling the conductivity-swelling trade-off. The optimal QAPI-70 membrane exhibited a conductivity of 130.2 mS cm −1 and a swelling ratio of only 22.1% at 80 °C, and retained 88.7% of its initial conductivity after 1000 h in 1 M NaOH at 80 °C. MD simulations provided supporting evidence for the superior microphase-separated morphology and OH − transport properties of QAPI-70. An AEMWE single cell based on this membrane delivered 1050 mA cm −2 at 1.8 V and 60 °C with stable operation over 100 h. This work provides a new strategy for developing high-performance AEMs, advancing AEMWE toward cost-competitive renewable green hydrogen production.