Critical aspects in exploring time analysis for the voltammetric estimation of kinetic parameters of surface electrode mechanisms coupled with chemical reactions

Abstract

The accurate determination of the rate constant related to the electron transfer step of so-called “surface redox active compounds” by voltammetric measurements is very important because it is linked to the reactivity and stability of many biological and chemical systems such as redox enzymes, vitamins, hormones, and many more. Evaluation of the kinetics of the electron transfer is often challenging, especially when chemical equilibria are coupled to the electron transfer step. In this work, we theoretically consider some critical aspects of the time-related methodologies in square-wave voltammetry (SWV), which is designed to analyze the kinetics of the electron transfer step of surface mechanisms coupled with chemical reactions. We demonstrate with a series of simulated scenarios that caution must be taken when exploring the time-related analysis for kinetic characterizations for both surface CE and EC mechanisms. The main concern stems from the fact that the SW frequency simultaneously affects both the kinetics of electron transfer and that of chemical reactions as well. Under defined conditions, the SW frequency variation in the case of surface EC and CE mechanisms may produce unexpected features of the voltammetric patterns. In many scenarios, time-independent analysis, such as those related to the square-wave amplitude and potential increment, are seen as alternative tools to evaluate the rate parameter of electrode reactions.