Koutecky-Levich analysis applied to nanoparticle modified rotating disk electrodes： Electrocatalysis or misinterpretation

• Published in: Nano research 2014-01, Vol.7 (1), p.71-78
• Main Authors: Masa, Justus, Batchelor-McAuley, Christopher, Schuhmann, Wolfgang, Compton, Richard G.
• Format: Article
• Language: English
• Subjects: Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Chemistry and Materials Science; Condensed Matter Physics; Diffusion rate; Electrocatalysis; Electrochemistry; Electrodes; Electrons; Materials Science; Nanocomposites; Nanomaterials; Nanoparticles; Nanostructure; Nanotechnology; Rate constants; Redox reactions; Research Article; Rotating disks; Voltammetry; 分析应用; 反应速率常数; 改性; 旋转圆盘电极; 氧化还原反应; 活性表面积; 电催化; 纳米粒子
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-013-0372-0

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 o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, 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 ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ 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.