Electrocrystallisation of cobalt, copper and cobalt–copper alloys on fluorine-doped tin oxide electrodes

Abstract

In this work, a systemic study of the Co, Cu and Co–Cu electrocrystallisation process was performed on a fluorine doped tin oxide coated conducting glass substrate. This was carried out in a sulphate solution of Na₂SO₄+H₃BO₃ (pH 3·8) without complexing agent. The influence of applied potentials on the electrochemical nucleation and growth has been studied, using cyclic voltammetry and chronoamperometry techniques. The cyclic voltammetry results clearly show that the potential of Co–Cu dissolution and their positive shifts depend on the cathodic limit and reveal a variation in the deposit composition when switching potential is varied. A number of kinetics parameters have been estimated from the analysis of current transients on the basis of the Scharifker–Hills model for electrochemical nucleation and diffusion controlled growth. From the analysis of the experimental current transients, it has been found that the nucleation mechanism is instantaneous with a typical three-dimensional nucleation and growth process for Co, Cu and Co–Cu respectively. A strong dependence of the number of active sites N₀ with applied potential is observed on the fluorine doped tin oxide surface.

Keywords:

• Electrodeposition
• Co–Cu alloy
• Cyclic voltammetry
• Chronoamperometry