Guidelines for the Voltammetric Study of Electrode Reactions with Coupled Chemical Kinetics at an Arbitrary Electrode Geometry.

Abstract

A powerful, unified, and simplifying mathematical approach for the theoretical treatment of first-order chemical kinetics coupled to interfacial charge transfers at electrodes of arbitrary geometry and size, both uniformly accessible and nonuniformly accessible to the electroactive species, is presented. The general CEC mechanism at spherical and disc electrodes is considered to test the validity and benefits of such an approach, based on the application of the so-called kinetic steady state, that enables the reduction of the multivariable problem of kinetic-diffusive differential equations to a single variable problem of a diffusion-only differential equation. This is solved both analytically and numerically, showing how this approach leads to general, simple, and efficient solutions for the study of the influence of coupled chemical kinetics on the voltammetric response. The voltammetry of the CEC mechanism is analyzed as a function of the kinetics and thermodynamics of the preceding and subsequent chemical reactions and of the electrode size (from macroelectrodes to ultramicroelectrodes) and shape (spherical and disc). Comparison with the responses of the CE, EC, and E mechanisms is included, proposing diagnosis criteria and procedures for quantitative analysis of experimental data.