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

Abstract

The rise of heterocycle cations, a new class of stable cations, has fueled faster growth of research interest in heterocycle cation-attached anion exchange membranes (AEMs). However, once cations are grafted onto backbones, the effect of backbones on properties of AEMs must also be taken into account.In order to comprehensively study the influence of cations effect and backbones effect on AEMs performance, a series of AEMs were prepared by grafting spacer cations, heterocycles cations, and aromatic cations onto brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO) or poly(vinylbenzyl chloride) (PVB) backbones, respectively. Spacer cation [trimethylamine (TMA), N,N-dimethylethylamine (DMEA)]-attached AEMs showed general ion transportation and stability behaviors, but exhibited high cationic reaction efficiency. Heterocycle cation [1-methylpyrrolidine (MPY), 1-methylpiperidine (MPrD)]-attached AEMs showed excellent chemical stability, but their ion conduction properties were unimpressive. Aromatic cation [1-methylimidazole (MeIm), N,N-dimethylaniline (DMAni)]-attached AEMs exhibited superior ionic conductivity, while their poor cations stabilities hindered the application of the membranes. Besides, it was found that PVB-based AEMs had excellent backbone stability, but BPPO-based AEMs exhibited higher OH À conductivity and cation stability than those of the same cations grafted PVB-based AEMs due to their higher water uptake (WU). For example, the ionic conductivities (ICs) of BPPO-TMA and PVB-TMA at 80 °C were 53.1 and 38.3 mS cm À 1 , and their WU was 152.3 and 95.1 %, respectively. After the stability test, the IC losses of BPPO-TMA and PVB-TMA were 21.4 and 32.2 %, respectively. The result demonstrated that the conductivity and stability properties of the AEMs could be enhanced by increasing the WU of the membranes. These findings allowed the matching of cations to the appropriate backbones and reasonable modification of the AEM structure. In addition, these results helped to fundamentally understand the influence of cation effect and backbone effect on AEM performance.

Effects of Structurally Different Tertiary Amines on the Properties of Quaternized Anionic Exchange Membranes Potentially Applicable for Water Electrolysis

“…Differently from what was previously described for other PPOand PVBC-based membranes, [31] the AEMs of this work were found to show higher ionic conductivity when aminated with TMA (𝜎 TP = 14.4 mS cm −1 ), with respect to those aminated with N-MPip (𝜎 TP = 8.4 mS cm −1 ). TMA-based membranes also exhibited a higher WU and IEC.…”

Elastic and Conductive Cross‐linked Anion Exchange Membranes Based on Polyphenylene Oxide and Poly(vinyl alcohol) for H2‐O2 Fuel Cells

“…The alkaline stability of AEMs has a significant impact on the operational lifespan of fuel cells [40] . By immersing AEMs in a 1 M NaOH solution at 80 °C and recording changes in IEC and IC over 30 days, the ion stability of AEMs is revealed, while changes in mechanical properties are used to characterize the stability of the AEMs’ main chain.…”

Poly(phenylene oxide)-Based Anion Exchange Membranes Having Linear Cross-Linkers or Star Cross-Linkers

“…The preparation of BPPO refers to our reported work. 30 A 4 g amount of PPO was dissolved in 50 mL of chlorobenzene at 120 °C in a three-necked round-bottom flask, which was equipped with an inert gas protection device and a reflux condenser. Then, NBS was added.…”