Crown ether-based anion exchange membranes with highly efficient dual ion conducting pathways

Anion exchange membranes (AEMs) are a crucial constituent for alkaline fuel cells. As the core component of fuel cells, the low performance AEMs restrict the development and application of the fuel cells. Herein, the trade-off between the OH– conductivity and dimensional stability was solved by constructing AEMs with adequate OH– conductivity and satisfactory alkali resistance using Tröger's base (TB) poly (crown ether)s (PCEs) as the main chain, the embedded quaternary ammonium (QA) and Na+-functionalized crown ether units as the cationic group. Crown ether is an electron donator, and can capture Na+ to form Na+-functionalized crown ether units to conveniently transfer OH– and significantly promote the alkaline stability of the AEMs. The influence of the Na+-functionalized crown ether units on the performance of AEMs was studied in detail. The PCEs based AEMs show an obvious hydrophobic-hydrophilic microphase separation. These features make them ideal platforms for the OH– conduction applications. As expected, the as-prepared PCEs-QA-100% (100% is the degree of cross-linking) AEM with an ionic exchange capacity (IEC) of 2.07 meq g−1 has a high OH– conductivity of 159 mS cm−1 at 80 °C. Furthermore, the membrane electrode assemblies fabricated using the PCEs-QA-100% AEM possess a maximum power density of 291 mW cm−2 under the current density of 500 mA cm−2.