High-Performance Asymmetric Porous Anion Exchange Membrane with Controllable Morphology via Solvent Evaporation and Water Etching

Polymer-based asymmetric anion exchange membranes (AEMs) with accurately controllable morphologies are essential for membrane-based separation but are challenging to fabricate. A major barrier in this process is the lack of simple, environmentally friendly, and universal strategies for pore formation. Herein, a direct solvent evaporation and water etching (SEWE) method was developed for preparing asymmetric AEMs, and the basic principles of the SEWE method were carefully investigated and revealed. This approach avoided the problems mentioned above and provided an effective strategy for preparing asymmetric AEMs with the desired asymmetric structures and microphase separation. Additionally, both the diffusive dialysis (DD) and electrodialysis (ED) capabilities of the prepared asymmetric AEMs were significantly better than those of commercial membranes. For example, the Py-PEG-140 membrane with the thinnest dense separation layer exhibited an ultrahigh salt flux and current efficiency during ED, which were 25 and 17% higher than that of typical commercial Type 10 membranes, indicating the utility of the SEWE method in preparing high-performance AEMs.