Highly hydroxide-conducting hybrid anion exchange membrane with functional COF-enhanced ion nanochannels

Abstract

Abstract Anion exchange membranes with potentially high conductivity and stability are urgently demanded in alkaline anion exchange membrane fuel cells (AEMFCs). However, the design and preparation of novel hydroxide-conducting material remain grand challenges. Herein, we demonstrate a significantly enhanced hydroxide conduction hybrid membrane with multi-ion nanochannels assembled by embedding two-dimensional covalent organic framework (COF) sheets into one-dimensional comb-shaped poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) chains. Hydrophilic imidazole-based ionic liquids (im-IL) in-situ polymerize within the ordered pores of COF PI-2, forming long-range continuous ion channels. Then the poly ionic liquid-loaded covalent organic frameworks (im@PI-2) as a novel filler is embedded into imPPO to construct hybrid membranes with multi-ion nanochannels. A remarkable hydroxide conductivity of 147\xa0mS/cm (80\xa0°C and 100% RH) and a maximum power density of 140\xa0mW/cm2 are readily achieved for the hybrid membrane with 5\xa0wt% im@PI-2 content. Particularly, the chemical stability, thermal stability, mechanical properties, and swelling resistance of the hybrid membrane are dramatically promoted by the introduction of im@PI-2. Meanwhile, the transfer of hydroxide in hybrid AEM is investigated by molecular dynamics simulations, which clarify the significant role of PI-2 one-dimensional channels in elevating hydroxide transport.