Early stages of cobalt electrodeposition on FTO and n-type Si substrates in sulfate medium

The mechanism of cobalt electrocrystallization on fluorine-doped tin oxide (FTO)-coated conducting glass substrate has been studied and compared with results obtained on n-type Si electrodes. The initial stages of metal deposition from a solution of 0.25 M CoSO4, 1 M Na2SO4 and 0.5 M H3BO3 (pH 3.5) were investigated using cyclic voltammetry, and chronoamperometry measurements. Important kinetics parameters were 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 was found that the process of cobalt deposition involves a three-dimensional (3D) electrochemical nucleation and diffusion-controlled growth. A strong dependence of the number density of active sites N0 with applied potential was observed on both FTO and n-type Si electrodes.