Graduate School of Engineering, Nagasaki University, 1-14 Bunkyo, Nagasaki 852-8521, Japan.
Anal Chem. 2023 Jul 4;95(26):9822-9830. doi: 10.1021/acs.analchem.3c00635. Epub 2023 Jun 19.
In redox-active ionic liquids (RAILs), either or both of the constituent ions are redox-active. Because of the high concentration of the ions, RAILs exhibit not only ion conduction but also electron conduction through the bimolecular electron self-exchange reaction. Because neat RAILs do not contain any supporting electrolyte, migration of the redox active ions results in enhancement or diminishment of the redox current at an electrode. To treat the migration effect for electrochemical analysis, a limiting current correction was theoretically derived by Oldham, Hyk, and Stojek (Oldham, K. , , 91-126; Hyk, W.; Stojek, Z. , , 4805-4813) for the steady-state voltammetry. Although steady-state voltammetry is a robust method in electrochemistry, the actual measurement is time-consuming and cannot be always made because of the instability of the electrochemical system. To overcome the problem, we propose the use of cyclic voltammetry to evaluate the diffusion coefficient of the redox-active ion that constitutes RAIL. The peak currents were analyzed by the purely diffusional framework of the Aoki-Matsuda-Osteryoung equation (Aoki, K.; Akimoto, K.; Tokuda, K.; Matsuda, H.; Osteryoung, J. , , 219-230.) in the range from several mV s to several ten mV s, and the migration correction to the near-steady-state limiting current was applied on the basis of the Oldham-Hyk-Stojek theory to scale the diffusion coefficient. As an example of RAILs, [FcCImC][TFSI], which exhibits charge increase reaction with the same sign (S - e ⇌ P), was used and the cyclic voltammograms were recorded at various sizes of the microdisk electrodes and various scan rates. The peak currents obeyed the Aoki-Matsuda-Osteryoung equation with the scaled diffusion coefficient, which has the same value as determined by the steady-state voltammogram. Our approach can be used to evaluate the diffusion coefficient of redox-active ions that constitute the RAIL with the charge increase reaction with the same sign.
在氧化还原活性离子液体（RAILs）中，构成离子的两者之一或两者都是氧化还原活性的。由于离子的高浓度，RAILs 不仅表现出离子传导，而且还通过双分子电子自交换反应表现出电子传导。由于纯 RAILs 不含任何支持电解质，氧化还原活性离子的迁移导致在电极处的氧化还原电流增强或减弱。为了处理电化学分析中的迁移效应，Oldham、Hyk 和 Stojek（Oldham，K.，，91-126；Hyk，W.；Stojek，Z.，，4805-4813）从理论上推导出了稳态伏安法的极限电流校正。尽管稳态伏安法是电化学中的一种稳健方法，但由于电化学系统的不稳定性，实际测量可能会很耗时，并且并不总是可行的。为了克服这个问题，我们提出使用循环伏安法来评估构成 RAIL 的氧化还原活性离子的扩散系数。在几 mV s 到几十 mV s 的范围内，通过 Aoki-Matsuda-Osteryoung 方程的纯扩散框架（Aoki，K.；Akimoto，K.；Tokuda，K.；Matsuda，H.；Osteryoung，J.，，219-230.）分析峰值电流，并应用 Oldham-Hyk-Stojek 理论对近稳态极限电流进行迁移校正，以标度扩散系数。作为 RAILs 的一个例子，使用了[FcCImC][TFSI]，它表现出具有相同符号（S - e ⇌ P）的电荷增加反应，并且在各种尺寸的微盘电极和各种扫描速率下记录了循环伏安图。峰值电流遵循带有标度扩散系数的 Aoki-Matsuda-Osteryoung 方程，该扩散系数与稳态伏安法确定的扩散系数相同。我们的方法可用于评估具有相同符号电荷增加反应的构成 RAIL 的氧化还原活性离子的扩散系数。
