Cation–dipole interaction that creates ordered ion channels in an anion exchange membrane for fast OH− conduction

Abstract

Precise control over polyelectrolyte architecture, engineered for self-assembly of ion-conducting channels, is of fundamental and technological importance to many fields, for example, fuel cells and redox flow batteries and electrodialysis. Building on recent advances with the supramolecular chemistry, we introduce inter/intra-molecular cation–dipole interactions between pendent quaternary ammoniums cations and polar polyethylene glycol grafts in an anion-exchange membrane (AEM). Such interactions lead to desirable, ordered ion-conducting pathways when in the membrane form. Comparison of the results of molecular dynamics simulation with 1H NMR and nano-scale microscopy analyses show that the cation–dipole interactions enhance self-assembly and the formation of interconnected ionic network domains, providing three-dimensional pathways for both water and ion transport. The resultant AEM exhibits high OH− conductivity (49 mS cm−1 at 30°C) and a completive peak power density of 622 mW cm−2 at 70°C when tested in a H2/O2 single-cell alkaline membrane fuel cell.