Potentiostatic Current Transient for Multiple Nucleation: A Limited-Diffusion Process Description

Abstract

Potentiostatic current transient is widely used to analyze the diffusion controlled three-dimensional nucleation process. SH model has a satisfied performance for almost all potentiostatic testing. However, some deviations between experimental results and the SH model's expression at decreasing period were reported. In this paper, we describe the deviation as resulting from diffusion depth is limited in electrolytic cell. Through a stochastic model is proposed, we derive an equation to describe reaction near the electrode surface of solute ions and their migration out of the diffusion zone. The theoretical model describes a limited-diffusion process using hemispherical nucleus revealed in SH model and Brownian motion in MD model. This model give a detail description of multiple nucleation process during electrodeposition. Based on the descriptions, it can be seen that SH model is a limiting case of our model, as diffusion depth R →+∞. And the equations also reveal the relationship between SH model and our new model. In addition, our theoretical equations are powerful enough to reproduce the potentiostatic current transient curves obtained from gold electrodepositing process. This work advances earlier models a step further and gives an explanation for the deviations between experimental data and standard model's description.