Quaternized poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes with pendant sterically-protected imidazoliums for alkaline fuel cells

Sheng, Weibing; Zhou, Xixing; Wu, Lexuan; Shen, Yinghua; Huang, Yingda; Liu, Lei; Dai, Sheng; Li, Nanwen

doi:10.1016/j.memsci.2020.117881

Cited by 55 publications

(14 citation statements)

References 42 publications

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“…In another study, the chemical stability of imidazolium was elevated by increasing steric hindrance in the positions of the cation rings. [51] The cations of PPO-BIm and PPO-NMIm were not stable, and the IC loss of PPO-TMIm was 83 % after soaking in 1 m NaOH at 80 °C for 192 h, while PPO-TPIm retained 86.7 % of IC after the stability test.…”

Section: Comprehensive Performancementioning

confidence: 95%

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

et al. 2021

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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.

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Section: Comprehensive Performancementioning

confidence: 95%

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

et al. 2021

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“…The chemical structures of imidazolium-based AEMs are illustrated in Figure . The degree of substitution X in our work is 30%, based on our previous experiment . All atomistic models of these polymers were constructed and optimized.…”

Section: Simulation Methodsmentioning

confidence: 99%

“…However, further improvement of imidazolium stability in strong alkaline environment remains essential for long-term applications. The alkaline stability is able to be tuned by the introduction of electron-donating or bulky substituents on imidazolium moieties. , Lin et al and Zhu et al proved the importance of electron-donating methyl substituent at the C2, C4, and C5 sites for improving alkaline stability. , More recently, our group reported that the AEM with bulky phenyl substituents at the C2, C4, and C5 imidazolium sites has excellent alkaline stability, but its OH – conductivity (22.5 mS/cm at 80 °C) still does not meet the application . To solve this problem, Gao et al prepared the imidazolium-based AEMs with alkyl spacer chains between poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and imidazoliums and AEMs with 6-carbon alkyl spacer chains that showed higher OH – conductivity than that with 1-carbon spacer chains .…”

Section: Introductionmentioning

confidence: 91%

Tunable OH^– Transport and Alkaline Stability by Imidazolium-Based Groups of Poly(2,6-dimethyl-1,4-phenylene oxide) Anion Exchange Membranes: A Molecular Dynamics Simulation

Zhou

Zhang

et al. 2021

Ind. Eng. Chem. Res.

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Imidazolium-based groups are promising organic cations in anion exchange membrane (AEM) materials. To investigate the effect of the imidazolium structure on OH − transport and alkaline stability of AEMs, we performed molecular dynamics simulation studies on hydrated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) AEMs with imidazoliums modified by various substituents and/or alkyl pendent/spacer chains. Imidazoliums with the methyl or phenyl substituent at the C2, C4, and C5 sites or alkyl pendant chains at the N3 site show a steric effect on the distribution of water and OH − around imidazoliums, which inhibits the OH − transport but increases the alkaline stability of AEMs. By introducing alkyl spacer chains, the enhanced hydration structure of imidazolium promotes OH − transport, but the weakened steric effect of PPO on imidazolium decreases alkaline stability. We elucidate that the PPO AEMs modified by 1,2,4,5-tetramethylimidazolium and alkyl spacer chains with six or eight aliphatic carbons show good balance between OH − transport and alkaline stability of AEMs. Moreover, the complete hydration shells of both imidazolium and OH − enhance the OH − transport efficiency and decrease the possibility of imidazolium degradation with the hydration level more than six. Our work provides a design principle of imidazolium-based AEMs in fuel cell applications.

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“…[1][2][3][4][5][6] the preparation of high-performance AEMs. In recent years, a series of different cationic functional groups, including cyclic or spirocyclic QA, [39][40][41][42][43][44][45] imidazolium, [46][47][48][49][50][51][52] guanidinium, [53][54][55] pyridinium, [56] and quaternary phosphonium (QP) [57][58][59][60][61] are further modified and introduced into the structure of AEMs. Compared with the previously reported AEMs based on QA salts, these AEMs with modified cation groups display significantly improved properties, especially for their alkaline stability.…”

Section: Introductionmentioning

confidence: 99%

Progress in High‐Performance Anion Exchange Membranes Based on the Design of Stable Cations for Alkaline Fuel Cells

Tao

Wang

Zhao

et al. 2021

Adv Materials Technologies

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Solid alkaline fuel cells with anion exchange membranes (AEMs) have drawn wide attention and have become an important focus in the field of renewable energy cells in recent years due to their high electrode activity, potential application of non‐precious metal catalysts, and relatively low requirements for fuel purity. AEM is the central component in solid alkaline fuel cells, and plays the role of conducting ions, blocking fuel crossover and providing catalyst support in fuel cells. Its performance directly affects the efficiency and service life of fuel cells. With some exceptions, the majority of AEMs have relatively low hydroxide conductivity and poor durability, which cannot meet the requirements of practical applications. The past decade has witnessed great progress in AEM designs and stability. Various kinds of AEMs with different cationic structures have been designed, and their properties and application in fuel cells are investigated. This review provides a comparative investigation and summary of highlights from the design of cationic structures for AEMs, including cyclic and spirocyclic quaternary ammonium cations, modified quaternary phosphonium, modified imidazoles, guanidinium, and metal cations. The authors’ perspective on the remaining challenges and directions of AEMs research for future development are also discussed.

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Quaternized poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes with pendant sterically-protected imidazoliums for alkaline fuel cells

Cited by 55 publications

References 42 publications

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

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

Tunable OH^– Transport and Alkaline Stability by Imidazolium-Based Groups of Poly(2,6-dimethyl-1,4-phenylene oxide) Anion Exchange Membranes: A Molecular Dynamics Simulation

Progress in High‐Performance Anion Exchange Membranes Based on the Design of Stable Cations for Alkaline Fuel Cells

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Quaternized poly(2,6-dimethyl-1,4-phenylene oxide) anion exchange membranes with pendant sterically-protected imidazoliums for alkaline fuel cells

Cited by 55 publications

References 42 publications

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

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

Tunable OH– Transport and Alkaline Stability by Imidazolium-Based Groups of Poly(2,6-dimethyl-1,4-phenylene oxide) Anion Exchange Membranes: A Molecular Dynamics Simulation

Progress in High‐Performance Anion Exchange Membranes Based on the Design of Stable Cations for Alkaline Fuel Cells

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Tunable OH^– Transport and Alkaline Stability by Imidazolium-Based Groups of Poly(2,6-dimethyl-1,4-phenylene oxide) Anion Exchange Membranes: A Molecular Dynamics Simulation