Quaternary Ammonium Modified Zirconia Reinforced Porous Polybenzimidazole Ion-Solvating Membranes for High-Performance Alkaline Water Electrolysis

Polybenzimidazole (PBI)-based ion-solvating membranes (ISMs) show promise for alkaline water electrolysis (AWE) but suffer from a fundamental trade-off whereby strategies to enhance ionic conductivity typically compromise dimensional stability. Here, quaternary ammonium-functionalized zirconia (ZrO 2 ) nanoparticles are incorporated into a porous PBI matrix through rational interface engineering. The grafted cationic groups (−N + R 3 ) serve dual functions by forming electrostatic cross-links with deprotonated PBI sites to restrict swelling while simultaneously establishing continuous hydroxide transport pathways. This synergy design yields a membrane exhibiting ultralow swelling (4.02% in 10 wt % KOH at 80 °C) and high conductivity (area resistance of 0.12 Ω cm 2 ). When deployed in AWE, the optimized membrane achieves a current density of 2.85 A cm –2 at 2.0 V and 80 °C, representing a 2.86-fold enhancement over pristine PBI, and maintains remarkable stability, exceeding 1000 h. This work demonstrates that multifunctional interface design can simultaneously resolve conflicting performance metrics, thereby advancing practical implementation of PBI-based ISMs in next-generation water electrolyzers.