高度稳定的羟基吩嗪液流电池阳极电解液的分解途径和缓解策略,Journal of Materials Chemistry A

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高度稳定的羟基吩嗪液流电池阳极电解液的分解途径和缓解策略
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2021-09-07 , DOI: 10.1039/d1ta03655f
Nadeesha P. N. Wellala ₁ , Aaron Hollas ₁ , Kaining Duanmu ₂ , Vijayakumar Murugesan ₂ , Xin Zhang ₂ , Ruozhu Feng ₁ , Yuyan Shao ₁ , Wei Wang ₁

Affiliation

水性有机氧化还原液流电池是一种很有前途的大规模储能技术。氧化还原活性有机分子的稳定性越来越被认为是主要障碍之一。在延长液流电池循环过程中，7,8-二羟基吩嗪-2-磺酸 (DHPS) 发生脱磺化和酚类 C-O 键的还原反应，生成 7/8-羟基吩嗪-2-磺酸的混合物，并氢化芳香环系统。带电 DHPS、其环氢化产物和可变取代的羟基吩嗪的密度泛函理论 (DFT) 分析导致了一系列二羟基吩嗪异构体的开发，这些异构体提供了对取代模式对溶解性和稳定性的影响的深入了解。合成了七种二羟基吩嗪 (DHP) 异构体及其溶解度，电化学性能、液流电池循环性能和降解途径已被研究。根据理论和实验结果，1、4、6 和 9 位的羟基取代产生高度稳定的衍生物，而 2、3、7 和 8 位的取代产生不稳定的衍生物。1,4- 和 1,6-DHP 与亚铁/铁氰化物结合的流通池实现了高稳定性，时间容量损失分别为每天 0.029% 和 0.031%。发现 1,8- 和 2,7-DHP 的分解是由不可逆的氢重排（互变异构化）引起的，产生氧化还原惰性物质。这些结果提供了对吩嗪基阳极电解液的分解途径和缓解策略的详细理解，

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Decomposition pathways and mitigation strategies for highly-stable hydroxyphenazine flow battery anolytes

Aqueous organic redox flow batteries are a promising technology for large-scale energy storage. The stability of the redox active organic molecules is increasingly being recognized as one of the major hurdles. Upon extended flow battery cycling, 7,8-dihydroxyphenazine-2 sulfonic acid (DHPS) undergoes desulfonation and reduction of a phenolic C–O bond to yield a mixture of 7/8-hydroxyphenazine-2-sulfonic acid, as well as hydrogenation of the aromatic ring system. Density functional theory (DFT) analysis of the charged DHPS, its ring-hydrogenated products, and variably substituted hydroxy phenazines has led to the development of a series of dihydroxylated phenazine isomers which provide insight into the effects of substitution pattern on solubility and stability. Seven dihydroxyphenazine (DHP) isomers were synthesized and their solubilities, electrochemical properties, flow battery cycling performance, and degradation pathways have been investigated. Based on theoretical and experimental results, hydroxyl substitution at the 1, 4, 6 and 9 positions yields highly stable derivatives, while substitution at the 2, 3, 7, and 8 positions results in unstable derivatives. Flow cells of 1,4- and 1,6-DHPs coupled with ferro/ferricyanide achieved high stabilities, with temporal capacity loss of 0.029 and 0.031% per day, respectively. Decomposition of 1,8- and 2,7-DHPs were found to arise from irreversible hydrogen rearrangement (tautomerization), yielding redox-inactive species. These results provide a detailed understanding of decomposition pathways and mitigation strategies for phenazine-based anolytes, and can provide general design guidelines for the development of stable redox-active organics.

更新日期：2021-09-15

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