O. V. Grishenkova, A. V. Kosov, O. L. Semerikova, V. A. Isaev, Yu. P. Zaikov.
ABSTRACT
The problem of studying the initial stages of electrochemical phase formation by means of cyclic voltammetry was considered. Analytical expressions were derived for cyclic voltammograms and sizes of independent new-phase nuclei formed on an indifferent electrode under linear potential sweep conditions for cases of instantaneous and progressive nucleation with diffusion-controlled growth. It was found that the functions of the current on the overpotential depend differently on the scan rate in the considered limiting cases of nucleation. The results of the numerical simulation were presented. It was demonstrated that if nuclei appear in a narrow time interval long before the reversal point, their number does not change with a change in the scan rate and growth occurs under diffusion control, then the logarithmic dependences of the maximum and minimum currents on the scan rate have the slope of –1/2. The slope of such dependences is –3/2 if nuclei are formed before and after the reversal point and their number decreases with an increase in the scan rate. The results obtained in the model system KNO3-NaNO3-AgNO3 melt / iridium substrate / silver confirmed the possibility of using the proposed criteria for interpreting experimental cyclic voltammograms. It was detected that at low concentrations of depositing ions, which provide diffusion control of the process, both instantaneous and progressive nucleation can be realized in this system, depending on other experimental conditions.
KEY WORDS:
cyclic voltammogram, scan rate, nucleation, growth, diffusion, silver, nitrate melt
DOI: 10.31857/S0235010621030063