Insights into kinetics extraction of the homogeneous electrocatalytic reaction between TMPD and ascorbic acid by cyclic voltammetry

Abstract

• Reaction rate constant between TMPD •+ and AA is determined by a finite element model. • The waveform transition behavior hinders the kinetics extraction of redox mediation. • A rate constant of 2.61 (mol m −3 ) −1 s −1 is obtained from the proposed methodology. As a continued research interest for energy conversion and chemical analysis purpose, illustrating the reaction kinetics of homogeneous electrocatalytic reaction is crucial in the understanding of redox mediation process. In this paper, the reaction kinetics of the homogeneous electrocatalytic reaction between N,N,N’,N’-tetramethyl- para -phenylene-diamine (TMPD) and ascorbic acid (AA) is extracted via a 1D homogeneous electrocatalytic reaction model based on finite element methods. The experimental voltammograms reveal the waveform transition in terms of kinetic parameter and excess factor and an oxidative pre peak is observed at the scan rate of 1 mV s −1 . Based on the results above, the same 1D homogeneous electrocatalytic reaction model is employed for the extraction of reaction rate constant between TMPD •+ and AA. A transition region of the voltammetric waveform is illustrated under different scan rates and the methodology for the kinetics extraction under specific scan rate is defined. The obtained k e value is (2.61 ± 0.11 (mol m −3 ) −1 s −1 ) and this value is further verified by experimental voltammograms under various scan rates and substrate concentrations. In conclusion, the proposed kinetics extraction methodology reflects the electrocatalytic reaction between TMPD and AA. Also, the employment of waveform transition region facilitates the understanding of the redox mediation process.