Koutecky-Levich analysis applied to nanoparticle modified rotating disk electrodes: Electrocatalysis or misinterpretation?
Koutecky-Levich analysis applied to nanoparticle modified rotating disk electrodes: Electrocatalysis or misinterpretation?
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DOI：
10.1007/s12274-013-0372-0
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发表时间：
2014-01-01
期刊：
影响因子：
9.9
通讯作者：
Compton, Richard G.
中科院分区：
文献类型：
--
作者：
Masa, Justus;Batchelor-McAuley, Christopher;Compton, Richard G.
分析了朴素Koutecky-Levich分析在微纳米粒子修饰的部分覆盖非平面几何旋转圆盘电极上的应用。假设粒子的扩散场有很强的重叠，使得整个表面的传输是一维的，与时间无关，观察到的伏安响应反映了表观电化学速率常数k (app) (o)，等于描述纳米颗粒表面氧化还原反应的真实速率常数k (o)，以及总电活性表面积与旋转圆盘表面几何面积的比值psi。证明了Koutecky-Levich分析是适用的，并得出了I（-1）与omega（-1）的预期图，其中I是电流，omega是转速，但由此推断的电化学速率常数的值是k (app) (o)，而不是k (o)。因此，当psi < 1时，表面电催化可能被天真而错误地推断出来，而当psi < 1时，推断出的电化学速率常数将小于k (o)。此外，psi对观察到的旋转圆盘电极伏安图的影响是显著的，这表明在将Koutecky-Levich分析过于简单地应用于修改的旋转电极时需要小心，例如通常应用于分析可能的氧还原催化剂。
The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate constant k (app) (o) , equal to the true rate constant k (o) describing the redox reaction of interest on the surface of the nanoparticles and the ratio, psi, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I (-1) versus omega (-1) where I is the current and omega is the rotation speed but that the values of the electrochemical rate constants inferred are thereof k (app) (o) , not k (o). Thus, for psi > 1 apparent electrocatalysis might be naively but wrongly inferred whereas for psi < 1 the deduced electrochemical rate constant will be less than k (o). Moreover, the effect of psi on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.