Model for the Nucleation and Diffusion-Controlled Growth of Binary Alloy Nuclei under Potentiostatic Conditions

Abstract

An approach is proposed to perform a mathematical description of the electrochemical formation and growth of binary alloy nuclei on the surface of an indifferent electrode under constant supersaturation (overpotential). This approach considers the total flux of two species of deposited ions in the electrolyte bulk to the surface of hemispherical new-phase nuclei. The concentration profile is averaged with allowance for the mole fraction ratio of the components. The cases of instantaneous and progressive nucleation with diffusion-controlled growth are studied. The overlap of the diffusion zones of the nuclei is analyzed in terms of the Scharifker–Hills model. Equations are derived to calculate the apparent diffusion coefficient of deposited ions, the number of nuclei per unit electrode surface, and the steady-state nucleation rate.