Multiple Enhancement Effects of Crown Ether in Tröger’s Base Polymers on the Performance of Anion Exchange Membranes

Abstract

The development of anion exchange membranes (AEMs) is hindered by the trade-off of ionic conductivity, alkaline stability, and mechanical properties. Tröger’s base polymers (Tb-polymers) are recognized as promising membrane materials to overcome these obstacles. Herein, the AEMs made from Tb-poly­(crown ether)­s (Tb-PCEs) show good comprehensive performance. The influence of crown ether on the conductivity and alkaline stability of AEMs has been investigated in detail. The formation of hydronium ion-crown ether complexes and an obvious microphase-separated structure formed by the existence of crown ether can enhance the conductivity of the AEMs. The maximum OH– conductivity of 141.5 mS cm–1 is achieved from the Tb-PCEs based AEM (Tb-PCE-1) at 80 °C in ultrapure water. The ion-dipole interaction of the Na+ with crown ether can protect the quaternary ammonium from the attack of OH– to improve the alkaline stability of AEMs. After 675 h of alkaline treatment, the OH– conductivity of Tb-PCE-1 decreases by only 6%. The Tb-PCE-1-based single cell shows a peak power density of 0.202 W cm–2 at 80 °C. The prominent physicochemical properties are attributed to the well-developed microstructure of the Tb-PCEs, as revealed by TEM, AFM, and SAXS observations.

Electrospun Modified Polyketone-Based Anion Exchange Membranes with High Ionic Conductivity and Robust Mechanical Properties

“…Polarization and power density curve of a single cell using QAFPK-1-6-E and QAFPK-1-6-C at 50 °C (a). The comparison of the properties of electrospun polyketone-based AEMs and other literature work (b). ,,,,,,,− The red shaded region represents the cross-linked structure in the AEM molecular structure. The blue shaded region indicates that the fiber structure exists in the AEM.…”

Conductivity and Stability Properties of Anion Exchange Membranes: Cation Effect and Backbone Effect

“…The importance of WU on the AEMs performance has also been extensively recognized. [36,37] Water is the medium for transporting OH À , and the values of both IC and chemical stability are correlated with AEMs WU. [38,39] Besides, the cathodic oxygen reduction reaction in AEMFCs requires the participation of water, and WU of AEMs plays an important role in affecting the performance of AEMFCs.…”

Hydrophilic Microporous Polymer Membranes: Synthesis and Applications

“…[32] An AEMFC assembled with DMDPM-BP-QTB delivers a considerable maximum power density of 202 mW cm À 2 . [33] However, TB-based polymers may have poor chemical stability under harsh alkaline conditions ( Figure 5), [34,45] leading to a short lifetime. Thus, AEMs from microporous PIMs with chemically stable cationic functional groups are in great demand.…”

“…The formation of microphase separation morphology was further enhanced by the incorporation of incorporating crown ether, followed by quaternization and crosslinking (T-PCEs, Figure 2a). [33] The dipole interaction between the alkali metal ions and the crown ether leads to increased membrane hydrophilicity. Noting that the chemical stability of quaternary bicyclic ammonium groups in PIM-QTB may be poor under harsh alkaline conditions.…”