Effect of pH on the electrodeposition nucleation and growth mechanism of cuprous oxide

In this paper, we report the kinetics, nucleation, and growth mechanism of copper oxide electrodeposited on ITO from copper sulfate and lactic acid solutions at different pH values, using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). According to the cyclic voltammetry, the cathodic peak potential increases with increasing scan rate, indicating that the deposition of Cu 2 O is an irreversible process influenced by diffusion control. To further investigate the type of Cu 2 O nucleation, it was found that Cu 2 O followed diffusion-controlled three-dimensional transient nucleation by comparing the timing current curves with the Scharifker-Hills three-dimensional nucleation model. Furthermore, the three-dimensional transient nucleation was still followed regardless of the deposition potential and pH variation; this result was also confirmed from field emission scanning electron microscopy (FE-SEM). According to the EIS profile, the charge transfer resistance of Cu 2 O decreased with the increase in deposition potential; the charge transfer resistance was the smallest at pH = 9. In the timing current curve D (diffusion coefficient) showed a decreasing trend with increasing pH values. The nucleation pattern and growth process of nuclei at the early stage of electrodeposition are the basis for the formation of thin films, which is a guideline for obtaining films with better performance.