Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States.
Anal Chem. 2016 Feb 2;88(3):1742-7. doi: 10.1021/acs.analchem.5b03965. Epub 2016 Jan 12.
We demonstrate a new experimental approach to measure heterogeneous electron transfer rates. We adapted the classical Koutecký-Levich model for a rotating disk electrode (RDE) to a general heterogeneous electrochemical kinetic study with ultramicroelectrodes (UMEs) even for fast redox systems, where different sizes of UMEs are used to modulate the mass transfer rate (m). Subsequently, a linear plot of (1/current density) vs 1/m at different potentials can be created from the obtained steady state voltammograms, which is analogous to the traditional Koutecký-Levich plot. A simple numerical treatment with a slope and y-intercept from a linear plot allows for extracting kinetic parameters. A unifying treatment is presented for the steady state quasi-reversible, irreversible, and reversible voltammograms for a simple electron transfer reaction at UMEs. This new experimental approach with submicrometer to ∼ micrometer sized UMEs exceeds the mass transfer rates achieved by conventional electrochemical methods using rotating electrodes or solely tens of micrometer sized electrodes, thus enables us to study much faster heterogeneous electron transfer kinetics with simple instrumentation. The method should be particularly useful in studying particle size and structure effects.
我们展示了一种新的实验方法来测量非均相电子转移速率。我们将经典的 Koutecký-Levich 模型应用于旋转圆盘电极（RDE），以进行更通用的非均相电化学动力学研究，即使是对于快速氧化还原体系，也可以使用不同尺寸的微电极（UME）来调节传质速率（m）。随后，可以从获得的稳态伏安图中在不同电位下创建（电流密度）与 1/m 的线性图，这类似于传统的 Koutecký-Levich 图。通过线性图的斜率和 y 截距进行简单的数值处理，可以提取动力学参数。对于 UME 上简单的电子转移反应的稳态准可逆、不可逆和可逆伏安图，提出了一种统一的处理方法。这种使用亚微米到约微米尺寸的 UME 的新实验方法超过了使用旋转电极或仅数十微米尺寸的电极的传统电化学方法实现的传质速率，从而使我们能够使用简单的仪器研究快得多的非均相电子转移动力学。该方法在研究颗粒尺寸和结构效应时应该特别有用。
