Reverse Pulse Voltammetry at Spherical and Disc Microelectrodes: Characterization of Homogeneous Chemical Equilibria and Their Impact on the Species Diffusivities

Abstract

The value of the electrochemical technique Reverse Pulse Voltammetry (RPV) for the characterization of chemical equilibria in solution is theoretically investigated. For this, the RPV response of the square scheme is studied at spherical and disc electrodes of any size assuming that the chemical reactions are at equilibrium. When the effective diffusion coefficients of the oxidized and reduced species are the same, analytical solutions are reported for both electrode geometries. Otherwise, a rigorous analytical solution is derived for spherical electrodes whereas the case of microdiscs is addressed by numerical simulations.The theory for the square scheme enables the study of the RPV response in very different situations, including the cases where the electrochemical and/or chemical transformations alter significantly the species diffusivity such as in electron transfer processes in room temperature ionic liquids or in the association of the electroactive species with (bio) macromolecules and nanoparticles. It is found that, when medium-size (disc or spherical) microelectrodes are employed, the RPV method enables the simultaneous determination of the effective diffusion coefficients of the oxidized and reduced species as well as the apparent formal potential. These magnitudes make it possible a sound physicochemical characterization of the system.