General Explicit Mathematical Solution for the Voltammetry of Nonunity Stoichiometry Electrode Reactions: Diagnosis Criteria in Cyclic Voltammetry.

Electrochemical reactions can effectively follow nonunity stoichiometries as can be found in the electrochemistry of halides, hydrogen, and metal complexes. The voltammetric response of these systems shows peculiar deviations with respect to the well-described features of the 1:1 stoichiometry. With the aim of specifying such differences, a rigorous and manageable analytical theory is deduced for the complete characterization of reversible electrode processes with complex stoichiometry in cyclic voltammetry (CV) at macroelectrodes. Particularly, the main features of the CV of 2:1, 1:2, 3:1, and 1:3 processes (that is, the peak currents and potentials and the influence of the scan rate and of the species concentration and diffusion coefficients) are given and compared with the 1:1 case in order to propose unambiguous diagnostic criteria of the stoichiometry of the electrode reaction. Also, expressions for the concentration profiles and surface concentrations of the redox species are given.