SCANNING ELECTROCHEMICAL MICROSCOPY .12. THEORY AND EXPERIMENT OF THE FEEDBACK MODE WITH FINITE HETEROGENEOUS ELECTRON-TRANSFER KINETICS AND ARBITRARY SUBSTRATE SIZE
SCANNING ELECTROCHEMICAL MICROSCOPY .12. THEORY AND EXPERIMENT OF THE FEEDBACK MODE WITH FINITE HETEROGENEOUS ELECTRON-TRANSFER KINETICS AND ARBITRARY SUBSTRATE SIZE
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DOI：
10.1021/j100183a064
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发表时间：
1992-02-20
影响因子：
--
通讯作者：
WIPF, DO
中科院分区：
文献类型：
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作者：
BARD, AJ;MIRKIN, MV;WIPF, DO
本文将扫描电化学显微镜（SECM）反馈模式的理论扩展到包括在基底上的有限非均相电子转移（et）动力学和任意基底尺寸的情况。理论治疗开发使用两个独立的方法：（i）多维积分方程的制定和数值解和（ii）交替方向隐式有限差分法。工作曲线和列表数据都提出了准可逆和不可逆的et反应的基板上。通过这种技术的测量等速率常数的范围被确定。快速异质et速率常数，高达1-20 cm s-1，应该是可测量的SECM反馈技术与范围的尖端尺寸目前采用（磁盘直径为2-25 μ m）。作为准可逆和不可逆系统的例子，分别用Ru（NH3）6（2+）在pH 4.0的水溶液中和Fe 2+在1 M H2SO 4中在玻璃碳电极上的氧化实验对理论处理进行了补充。扩散控制反馈的模拟电流-距离曲线给出了一系列基板尺寸;在某些条件下，导电功能比尖端电极小10-20倍，应可识别SECM。Ru（NH_3）_6（2+）在不同尺寸的Pt超微盘电极上的氧化实验与SECM中有限衬底效应的理论预测一致。
The theory of the feedback mode of the scanning electrochemical microscope (SECM) is extended to include the cases of both finite hetergeneous electron-transfer (et) kinetics at the substrate and arbitrary substrate sizes. Theoretical treatments are developed using two independent approaches: (i) the formulation and numerical solution of multidimensional integral equations and (ii) the alternating direction implicit finite-difference method. Working curves and tabulated data are presented for both quasi-reversible and irreversible et reactions on the substrate. The range of et rate constants accessible to measurement via this technique is identified. Fast heterogeneous et rate constants, up to 1-20 cm s-1, should be measurable by SECM feedback techniques with range of tip sizes currently employed (disks with diameters of 2-25-mu-m). The theoretical treatments are complemented with experiments on the oxidation of Ru(NH3)6(2+) in aqueous solutions of pH 4.0 and of Fe2+ in 1 M H2SO4 at glassy-carbon electrodes, as examples of quasi-reversible and irreversible systems, respectively. Simulated current-distance curves for diffusion-controlled feedback are given for a range of substrate sizes; under certain conditions, conductive features 10-20 times smaller than the tip electrode should be identifiable by SECM. Experiments involving the oxidation of Ru(NH3)6(2+) at Pt ultramicrodisk electrodes of different sizes, employed as model finite substrates, agree well with the theoretical predictions for finite substrate effects in SECM.