竞争性开环与霍夫曼消除路径在水性TEMPO正极电解液中的第一性原理研究
Competing Ring-Opening and Hofmann Elimination Pathways in Aqueous TEMPO Catholytes: A First-Principles Study
- Sorbonne Université（索邦大学）
- CNRS, Physico-Chimie des Electrolytes et Nanosystèmes Interfaciaux, PHENIX（法国国家科学研究中心，界面电解质与纳米系统物理化学，PHENIX）
- Réseau sur le Stockage Electrochimique de l’Energie (RS2E)（电化学储能研究网络 (RS2E)）
- Institut Universitaire de France (IUF)（法兰西学院）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过第一性原理计算发现，水性TEMPO正极电解液的降解以开环路径为主，其活化自由能低于霍夫曼消除，且官能化显著影响稳定性。
AI中文摘要：
基于TEMPO衍生物的水性液流电池在大规模储能方面具有广阔前景，但其实际应用受到氧化态N-氧代铵离子化学不稳定性的限制。在本工作中，我们利用从头算分子动力学结合增强采样方法研究了五种TEMPO衍生物的降解过程。考察了两种提出的降解机制，即开环和霍夫曼消除，并比较了它们相应的活化自由能。对于所考虑的所有衍生物，开环表现出比霍夫曼消除更低的活化自由能，表明开环是动力学上更优选的降解路径。然而，开环势垒的大小在不同分子之间差异显著，表明不同的官能化方式强烈影响其抗降解稳定性。预测的开环偏好与现有实验研究一致，这些实验已识别或推断出多种基于TEMPO的正极电解液发生开环降解。这些结果提供了难以通过实验分辨的降解路径的原子级图像，并强调了分子结构在控制水性电解液中TEMPO衍生物动力学稳定性方面的重要性。
英文摘要：
Aqueous redox-flow batteries based on TEMPO derivatives are promising for large-scale energy storage, but their practical use is limited by the chemical instability of the oxidized N -oxoammonium state. In this work, we investigate the degradation of five TEMPO derivatives using ab initio molecular dynamics combined with enhanced sampling. Two proposed degradation mechanisms, ring opening and Hofmann elimination, are examined and their corresponding activation free energies are compared. For all derivatives considered, ring opening exhibits a lower activation free energy than Hofmann elimination, identifying it as the kinetically preferred degradation pathway. The magnitude of the ring-opening barrier, however, varies significantly between molecules, showing that different functionalizations strongly influence its stability toward degradation. The predicted preference for ring opening is consistent with available experimental studies, which have identified or inferred ring-opening degradation for several TEMPO-based catholytes. These results provide an atomistic picture of degradation pathways that are difficult to resolve experimentally and highlight the importance of molecular structure in controlling the kinetic stability of TEMPO derivatives in aqueous electrolytes.
