Kinetic Influence of Surface Charge Transfer Reactions Preceded by Non-Electrochemical Processes on the Response in Cyclic Voltammetry

A general analytical explicit expression for the response of a surface charge transfer preceded by a non-electrochemical process has been deduced. This solution is applicable to any electrochemical technique independent of the rates of both reactions. Interesting simplified cases are obtained for very common experimental situations in which the rates of electrochemical and non-electrochemical steps are similar. These expressions have been applied to cyclic voltammetry in order to analyze the kinetic influences on the current-potential response and to propose procedures for determining the rate and equilibrium constants of the mechanism. Moreover, it has been obtained an apparent rate constant of the overall process that reduces to a pure non-electrochemical rate-limiting process or to a pure electrochemical rate limiting one, under the right conditions. Experimental verification of the theoretical framework has been done with the analysis of the host-guest complexation between a surface confined electroactive ferrocene moiety and a solution soluble cyclodextrin in a water-ethanol media. From the dynamic analysis of the influence of the scan rate on the cyclic voltammetry curves, values have been obtained for the binding constant (4.96x105M-1) and rate constants for the inclusion complex formation and dissociation showing the great stability of the electro-inactive ferrocene-cyclodextrin complex.