Abstract
A theoretical model describing the transport and kinetic processes involved in heterogeneous redox catalysis of solution phase reactants at electrode surfaces coated with redox active monolayers is presented. We describe theoretically the time dependent chronoamperometric response expected for a redox active monolayer in the absence of a substrate in solution, and subsequently extend the analysis to consider the reaction of a solution phase substrate mediated by surface immobilized redox groups. This is accomplished via a Laplace transform based solution of the Fick diffusion equation for the substrate transport to the monolayer surface coupled with the development of a suitable flux matching condition at the monolayer/solution interface . The latter procedure enables the development of an analytical expression for the transient current response in terms of well established mathematical special functions. We have shown that kinetic information may be readily extracted from the developed expressions for the current response as a function of time. In the present paper we assume that the reaction between mediator and substrate is of a simple outer sphere bimolecular type.
Highlights
The phenomenon of heterogeneous redox catalysis at electrode surfaces has been studied extensively over the last twenty years
Previous theoretical work describing mediated redox catalysis at monolayers in the context of rotating disc voltammetry has been presented by Andrieux and Saveant [5], and Laviron [6], More recently the analysis has been extended to a time dependent technique such as cyclic voltammetry by Aoki and co-workers [7] and by Xie and Anson [8,9,10]
In the present communication we have presented a theoretical analysis describing the chronoamperometric response arising from the mediated electron transfer of a solution phase substrate at a redox active monolayer
Summary
The phenomenon of heterogeneous redox catalysis at electrode surfaces has been studied extensively over the last twenty years. It is interesting to note that the technique of potential step chronoamperometry has not been used in any extensive manner to examine mediated electron transfer processes at redox active monolayers This is surprising given that the technique is simple both in concept and in execution. In this paper we initially describe theoretically the chronoamperometric response expected for a redox active monolayer firstly in the absence of a substrate in solution, and subsequently extend the analysis to consider the reaction of a solution phase substrate mediated by surface immobilized redox groups. We address the main issue of the present paper, that of mediated electron transfer between a solution phase reactant and a redox site immobilized at a monolayer coverage on a support electrode surface. In the following we focus attention totally on the catalytic term
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