Enhanced Hydroxide Conductivity In Zwitterionic Polyacrylate-Based Anion Exchange Membranes Via Side-Chain Length Optimization

Abstract

Anion exchange membranes (AEMs) have garnered significant attention as the essential parts of various sustainable energy conversion devices. However, their practical application remains restricted by the insufficient conductivity and poor chemical stability. Particularly, the limited understanding of the relationship between structure and conductivity hinders further development. To address these challenges, this work focuses on constructing novel polyacrylate-based AEMs decorated with pendant zwitterions (designated as PSBPA-X, BSBPA-X, where X=20, 30, 40). The the spacer length between the zwitterions is strategically adjusted to enhance the hydroxide conductivity. Atomic force microscopy (AFM) analysis reveals that a longer spacer length between the zwitterions promotes the microphase separation and the formation of advanced water channels, which facilitates the OH- transport in BSBPA-40 membrane. Moreover, the stronger electrostatic potential and lower interaction energy between the BSBPA-40 and OH- further contributes to efficient OH- hopping transmission. Consequently, the BSBPA-40 membrane demonstrates the highest OH- conductivity, achieving 102.1 mS/cm at 80℃ and 90% relative humidity. Additionally, the BSBPA-40 membrane maintains excellent thermal stability, mechanical performance and alkaline stability under various testing conditions. Furthermore, the BSBPA-40 membrane-based zinc-air battery achieves an outstanding powder density of 156.7 mW/cm2 at room temperature, while its water electrolysis performance reaches 2.1 A/cm2 at 2.0 V. These results indicate that the developed membranes holds great promise for applications in the sustainable and clean energy technologies.

Keywords: zwitterions, polyacrylate, structure-conductivity, zinc-air battery, water electrolysis