(423e) Anion Exchange Membranes with Maximized Combination of Durability and Conductivity

Anion exchange membranes (AEMs) are recently being heavily investigated due to their potential use in electrochemical devices, such as fuel cells and electrolyzers, in order to promote the societal adoption of renewable-energy infrastructure. Due to the intermittent nature of renewable energies, it is envisioned that excess renewable energy from solar, wind, etc. could be stored in the chemical bond form of hydrogen, which then could be utilized to produce electricity via fuel cells when demand exceeds supply, or to power other applications, such as vehicles. To be used in electrochemical devices for economically-viable renewable energy storage and usage, AEMs must have good mechanical durability and alkaline stability as well as have high ion conductivity. To achieve all three necessary properties simultaneously, we have developed a new class of AEMs by following three design criteria. First, the polymer backbone consists of all carbon-carbon linkages to ensure good alkaline stability. Second, quaternized ammonium head-groups are tethered to the polymer backbone via a flexible alkyl chain to promote high alkaline stability and high anionic conductivity. Lastly, crosslinking is used to enhance the mechanical and dimensional stability under hydrated operational conditions. By following the aforementioned strategies, crosslinked polyphenylene AEMs were synthesized and demonstrated excellent alkaline stability (negligible IEC loss after submersion in 1M NaOH_(aq) at 80 °C for 1,000 h), superior mechanical properties (stress ≥ 40 MPa, strain ≥ 140 %), excellent OH^- conductivity (≥ 130 mS/cm) and promising electrolyzer performance (< 1.8 V, 500 mA/cm², 45 µm).