Differential double pulse voltammetry at spherical microelectrodes for the characterization of the square mechanism

• Analytical solution for the square mechanism in DDPV at spherical microelectrodes.
• It covers physicochemical processes at equilibrium altering notably species diffusion.
• Singular behaviours are reported at spherical microelectrodes for such processes.
• Methodology and optimum conditions are proposed for the system characterization.

A rigorous analytical solution is presented for the study of chemical equilibria coupled to reversible electron transfers by means of differential double pulse voltammetry (DDPV) at (hemi)spherical electrodes. Special attention is paid to situations where the chemical processes in solution involve a significant change in the diffusivity of one of the electroactive species. This leads to a more complex behaviour of the DDPV response at microelectrodes with respect to the case of equal effective diffusion coefficients. The impact of such behaviour on the variation of the DDPV peak with the technique parameters (double pulse duration and pulse amplitude) and with the electrode size is discussed. Also, experimental conditions and methodology for the determination of the diffusion coefficients, formal potential and equilibrium constants are proposed.

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