Self-aggregating cationic-chains enable alkaline stable ion-conducting channels for anion-exchange membrane fuel cells

Abstract

Precise manipulation of the polyelectrolyte self-assembly process, to form the desired microstructure with ion-conducting channels, is of fundamental and technological importance to many fields, such as fuel cells, flow batteries and electrodialysis. To fabricate anion exchange membranes (AEMs) with highly conductive and alkaline stable ion-conducting channels, we hereby report a strategy for designing self-aggregating side chains with optimized alkaline stability, by inserting dipolar ethylene oxide (EO) spacers in the cationic side chain. Simulation and nano-scale microscopy analyses verify the self-assembly process of the flexible side chain with cation–dipole interaction to construct interconnected ionic highways for fast water and ion transportation. The resulting O-PDQA AEM exhibits higher hydroxide conductivity (106 mS cm⁻¹ at 80 °C) and a competitive peak power density (1.18 W cm⁻² at 70 °C) in alkaline H₂/O₂ single-cell fuel cells. Moreover, O-PDQA shows excellent alkaline stability with over 96% conductivity retention after storage in 2 M NaOH solution at 80 °C for 1080 h. This new concept of introducing dipolar moieties in the cationic side chain can accelerate the development of technologies that involve polyelectrolytes.