Design of Efficient and Mechanically Robust Anion Exchange Membrane for Water Electrolysis Achieved by Chemically Crosslinked Elastomers using Polyfluorene-Based Conjugated Polymers

Anion exchange membrane water electrolysis (AEMWE) is a promising technology for green hydrogen production. However, current anion exchange membranes (AEMs) face challenges in maintaining performance and mechanical durability under the high-temperature and alkaline operating conditions of AEMWE. To address these limitations, crosslinked elastomeric AEMs are developed using styrene-ethylene-butylene-styrene (SEBS) functionalized with dimethyl amine side chains as the host polymer and polyfluorene incorporated with different aromatic spacers as the crosslinker. By tuning the hydrophobicity of the crosslinkers, the optimized AEM produces inter-connected ionic domains, exhibiting a high ionic conductivity (124 mS cm⁻¹ at 80 °C) and alkaline stability (97.6% retention after 1000 h in 1 m KOH at 80 °C). Consequently, the AEMWE single-cell achieves an impressive current density of 14.0 A cm⁻² at 2.0 V and 80 °C in 1 m KOH using a PtRu/C cathode and Ni₂Fe anode catalysts. In addition, the AEMWE single cell operates stably for over 300 h under the demanding conditions of 1.0 A cm⁻² and 80 °C. This work highlights the potential of newly designed crosslinked elastomeric AEMs for the application in AEMWEs.