On the diffusion of ferrocenemethanol in room-temperature ionic liquids: an electrochemical study
On the diffusion of ferrocenemethanol in room-temperature ionic liquids: an electrochemical study
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DOI：
10.1039/c1cp20392d
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发表时间：
2011-01-01
影响因子：
3.3
通讯作者：
Walsh, Darren A.
中科院分区：
文献类型：
--
作者：
Lovelock, Kevin R. J.;Ejigu, Andinet;Walsh, Darren A.
采用循环伏安法、计时电流法和扫描电化学显微镜（SECM）研究了二茂铁甲醇（FcMeOH）在室温离子液体（RTIL）中的电化学行为。使用计时电流法测量的FcMeOH的扩散系数随着RTIL粘度的增加而降低。RTIL的质量传输特性的分析表明，斯托克斯-爱因斯坦方程不适用于我们的数据。的“相关长度”估计从扩散系数数据和对应的平均尺寸的孔（空隙）在液体中，这表明在这些液体中的扩散物种之间的孔跳跃的模型是适当的。在超微电极上的循环伏安法表明，在二茂铁甲醇氧化过程中记录稳态伏安图的能力取决于伏安扫描速率，电极尺寸和RTIL粘度。类似地，记录稳态SECM反馈接近曲线的能力取决于RTIL粘度、SECM尖端半径和尖端接近速度。使用1.3 μ m Pt SECM尖端，稳态SECM反馈接近曲线在RTIL中获得，只要尖端接近速度足够低以维持SECM尖端的稳态扩散。在尖端诱导对流的情况下，SECM尖端电流的贡献显着，这种效果可以占理论上使用质量传输方程，包括扩散和对流条款。最后，在二茂铁甲醇氧化过程中，通过电极/RTIL界面的非均相电子转移速率使用SECM进行了估计，在所研究的最低粘度RTIL中，k（0）至少为0.1 cm s（-1）。
The electrochemical behaviour of ferrocenemethanol (FcMeOH) has been studied in a range of room-temperature ionic liquids (RTILs) using cyclic voltammetry, chronoamperomery and scanning electrochemical microscopy (SECM). The diffusion coefficient of FcMeOH, measured using chronoamperometry, decreased with increasing RTIL viscosity. Analysis of the mass transport properties of the RTILs revealed that the Stokes-Einstein equation did not apply to our data. The "correlation length" was estimated from diffusion coefficient data and corresponded well to the average size of holes (voids) in the liquid, suggesting that a model in which the diffusing species jumps between holes in the liquid is appropriate in these liquids. Cyclic voltammetry at ultramicroelectrodes demonstrated that the ability to record steady-state voltammograms during ferrocenemethanol oxidation depended on the voltammetric scan rate, the electrode dimensions and the RTIL viscosity. Similarly, the ability to record steady-state SECM feedback approach curves depended on the RTIL viscosity, the SECM tip radius and the tip approach speed. Using 1.3 mu m Pt SECM tips, steady-state SECM feedback approach curves were obtained in RTILs, provided that the tip approach speed was low enough to maintain steady-state diffusion at the SECM tip. In the case where tip-induced convection contributed significantly to the SECM tip current, this effect could be accounted for theoretically using mass transport equations that include diffusive and convective terms. Finally, the rate of heterogeneous electron transfer across the electrode/RTIL interface during ferrocenemethanol oxidation was estimated using SECM, and k(0) was at least 0.1 cm s(-1) in one of the least viscous RTILs studied.