High-performance o-PBI membranes with continuous cavities for enhanced proton conductivity

Hydrogen separation and purification play a crucial role in the chemical industry. High-temperature electrochemical hydrogen pump (HT-EHP) technology based on polybenzimidazole (PBI) membranes has great potential for hydrogen purification, the key to this application lies in the design of PBI membranes with high proton conductivity. To achieve this, we optimized the spatial conformation of polymer chains by coordinating metal ions (Zn 2+ /Co 2+ ) with the imidazole groups in PBI, forming continuous coordination cavities. Molecular dynamics (MD) simulations revealed that the coordination between metal ions and imidazole induces polymer chain distortion, creating sub-nanometer coordination cavities (∼8 Å). Wide-angle X-ray scattering (WAXS) and wide-angle X-ray diffraction (WAXD) confirmed the existence of these coordination cavities. After the removal of metal ions, the residual cavities were filled with phosphoric acid (PA), constructing long-range ordered proton conduction pathways in the high-performance PBI membranes ( o -PBI-Zn and o -PBI-Co). Scanning electron microscopy (SEM) analysis showed that the continuous porous network within the polymer chains resembles a root-like structure, facilitating efficient three-dimensional proton transport. The resulting membranes exhibited excellent mechanical properties (tensile strength of 45 MPa) and outstanding proton conductivity (0.126 S/cm at 160 °C). When assembled into a HT-EHP, the membranes achieved a hydrogen purification rate of 9.22 mL (cm 2 ·min) −1 at 180 °C, with an energy consumption as low as 0.1 kWh/L(H 2 ). This study presents an innovative strategy for designing high-proton-conductivity PBI membranes, significantly enhancing their potential for HT-EHP applications, offering a promising alternative for hydrogen purification technologies.