Application notes 20 min read

CV Sim: Simulation of the simple redox reaction (E) – Part I: The effect of scan rate – Kinetics – Application Note 41-1

Latest updated: August 31, 2021

Abstract

In this note, the effect of the voltage scan rate on the shapes of the I vs. E curves is described for reversible and irreversible reactions. As a reminder, to investigate a redox system in the standard condition, one needs to make several CVs with different scan rates and to analyze the evolution of peak current Ip and peak potential Ep with the scan rate. If Ep is invariant and |Ip| is proportional to √v, it means the reaction is reversible (high k°). The diffusion coefficient DA and the standard potential E° of the reaction can be determined. If Ep varies with log(v) and |Ip| is proportional to √v, it means the reaction is irreversible (low k°). The symmetry factor αr and the standard constant k° of the reaction can be determined.
In a real experiment, the ohmic drop and the double layer capacitance current are not negligible. They must be taken into account, which is possible with CV Sim and is the subject of the second part of this application note.

 

Introduction

CV Sim is a powerful tool implemented in EC-Lab that allows the user to simulate current vs. potential curves resulting from a voltammetry experiment. A vast array of parameters can be modified, making CV Sim a very accessible tool to understand what kind of information can be obtained by voltammetry on the studied electrochemical system. In this application note, the simplest conditions are used:

 

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