Simulation of cyclic voltammograms for 3D diffusion-controlled growth and dissolution of new phase nuclei

The regularities of diffusion-controlled growth and dissolution of a large random ensemble of hemispherical nuclei on an indifferent macroelectrode surface are analyzed using the proposed model under potential sweep conditions. The model considers the relationship between the concentration profiles to the nucleus due to spherical diffusion and to the electrode due to planar diffusion, and the distribution function of Voronoi cell areas. The simulated cyclic voltammograms (CVs) reproduce all the characteristic features of experimental CVs for 3D nucleation/growth processes. The influence of the number density of nuclei and scan parameters on the calculated CVs is studied. It is shown that an increase in the scan rate and a decrease in the number density of nuclei can lead to a significant transformation of the CV cathodic part up to the formation of a current loop. Furthermore, a shift of the peak potential in the cathodic direction can be observed as the scan rate increases in the case of 3D diffusion-controlled growth. The discrepancy with the Berzins-Delahay model is discussed and an approach is proposed for determining the diffusion coefficient of depositing ions in the case of a nonlinear dependence of the peak current density on the square root of the scan rate. The influence of the Voronoi cell area and scan parameters on the nucleus size evolution and size distribution is analyzed.