Reeves Kyle G, Serva Alessandra, Jeanmairet Guillaume, Salanne Mathieu
Sorbonne Université, CNRS, Physico-chimie des électrolytes et nanosystèmes interfaciaux, PHENIX, F-75005, Paris, France.
Phys Chem Chem Phys. 2020 May 21;22(19):10561-10568. doi: 10.1039/c9cp06658f. Epub 2020 Feb 19.
Biredox ionic liquids are a new class of functionalized electrolytes that may play an important role in future capacitive energy storage devices. By allowing additional storage of electrons inside the liquids, they can improve device performance significantly. However current devices employ nanoporous carbons in which the diffusion of the liquid and the adsorption of the ions could be affected by the occurrence of electron-transfer reactions. It is therefore necessary to understand better the thermodynamics and the kinetics of such reactions in biredox ionic liquids. Here we perform ab initio molecular dynamics simulations of both the oxidized and reduced species of several redox-active ionic molecules (used in biredox ionic liquids) dissolved in acetonitrile solvent and compare them with the bare redox molecules. We show that in all the cases, it is necessary to introduce a two Gaussian state model to calculate the reaction free energies accurately. These reaction free energies are only slightly affected by the presence of the IL group on the molecule. We characterize the structure of the solvation shell around the redox active part of the molecules and show that in the case of TEMPO-based molecules strong reorientation effects occur during the oxidation reaction.
双氧化还原离子液体是一类新型的功能化电解质，可能在未来的电容式储能设备中发挥重要作用。通过允许在液体内部额外存储电子，它们可以显著提高设备性能。然而，目前的设备采用纳米多孔碳，其中液体的扩散和离子的吸附可能会受到电子转移反应的影响。因此，有必要更好地理解双氧化还原离子液体中此类反应的热力学和动力学。在这里，我们对溶解在乙腈溶剂中的几种氧化还原活性离子分子（用于双氧化还原离子液体）的氧化态和还原态进行了从头算分子动力学模拟，并将它们与裸氧化还原分子进行了比较。我们表明，在所有情况下，都需要引入双高斯态模型来准确计算反应自由能。这些反应自由能仅受到分子上IL基团存在的轻微影响。我们表征了分子氧化还原活性部分周围溶剂化壳的结构，并表明在基于TEMPO的分子的情况下，氧化反应期间会发生强烈的重新取向效应。
