Enhanced Strength and Proton Transport in DA‑PBI/SPEEK Composite Membranes via Hydrogen-Bond-Driven Interphase Engineering

High-temperature proton exchange membranes (HT-PEMs) suffer from an unavoidable trade-off between proton conductivity and mechanical strength under wide-temperature and anhydrous environments. Herein, copolymerized DA-PBI/SPEEK composite membranes are fabricated via hydrogen-bond-driven interphase engineering. The sulfonic acid groups of SPEEK form intense acid-base pairs with imidazole and amino sites on DA-PBI, the synergistic effects of flexible chain segments and intermolecular hydrogen bonding significantly enhance polymer miscibility and construct a robust acid-base interaction network. Quantum chemical calculations and charge density difference (CDD) analysis confirm that the nitrogen active sites of DA-PBI anchor phosphoric acid via electronic rearrangement, which remarkably lowers the energy barrier for proton migration. The optimal membrane achieves a tensile strength of 130 MPa (3.25 times that of pristine SPEEK) and a peak power density of 0.536 W cm −2 (1.85 times that of pristine SPEEK) at 160 °C. This multi-scale strategy combining molecular chain tailoring, interfacial modulation, and electronic structure optimization resolves the conductivity-mechanical property dilemma of PBI-based membranes, offering a promising route to advanced anhydrous HT-PEMs.