Comparison Between a Charge Transfer Process and an Electrocatalytic Process in Cyclic Voltammetry and Cyclic Voltcoulommetry. Application to the Oxidation of Ferrocyanide at a Ferrocene‐Monolayer Modified Gold Electrode

Abstract

Ferrocyanide oxidation catalyzed by a ferrocene-alkylthiolate monolayer at gold electrodes has been investigated by using cyclic voltammetry (CV) and cyclic voltcoulommetry (CVC). The voltammetric current-potential curves obtained present a stationary sigmoidal feature which points out to a very high rate constant for the chemical step, whereas the charge-potential curves do not reach an stationary behavior in any case. Simple expressions are presented for the characterization of the CV and CVC curves under Nernstian conditions for the charge transfer step. From these expressions, a value for the chemical rate constant 2.5 Â 10 4 M À1 s À1 has been easily obtained from an anodic plateau of the CV curves or from the linear anodic region of the CVC curves.

Analysis of the Electrochemical Response of Surface‐confined Bidirectional Molecular Electrocatalysts in the Presence of Intermolecular Interactions

“…The increase of the value of L gives rise to an increase in the limiting anodic and cathodic currents in agreement with Eqn. (40). Under Nernstian conditions (Figure 2A), there is no effect of L on the shape of the current-potential curves.…”

“…Scheme (II) corresponds to an extension of a previous case of binary monolayers of ferrocenylhexanethiol/1‐Hexanethiol with an irreversible chemical step (i. e., , only ferricyanide present in the solution) [39,40] . In this case, we have added both the reduced and the oxidised species to the solution such that the two cathodic and anodic catalytic reactions can take place.…”

“…with E I lim =2 being the potential at which the current is the half of the limiting anodic or cathodic values, given by Eqn. (40). By taking into account the approximate expression for the stationary current under Nernstian conditions when intermolecular interactions are considered (see Eqns.…”

“…The equilibrium constant (or its inverse) can be easily obtained from the ratio between the anodic and cathodic limiting currents (see Eqns. (40)). The change in K causes the shift of the response in the current axis.…”

“…These interactions can be considered from stochastic or phenomenological approaches, with the later being based on thermodynamic isotherms as Frumkin's one. [35] In this manuscript we develop an extension of a previous phenomenological ideal model, [39,40] devoted to the characterization of the voltammetric responses of a confined redox probe with an irreversible catalytic step. In this case, we have included the possibility of a bidirectional catalysis and the influence of intermolecular interactions under conditions where the electrostatic environment of the confined molecules determines the nature of intermolecular interactions.…”