Nano- and micrometric approaches to cobalt electrodeposition on carbon substrates

The first stages of electrodeposition of cobalt on different carbon substrates are studied at different [Cl-]/[Co(II)] ratios by Tapping mode atomic force microscopy, scanning electron microscopy and electrochemical analysis. Two charge deposition ranges are considered, ensuring that nano- and micrometric levels are attained. At the nanometric scale, a gradual increase in the number of nuclei over time is observed but, below a critical value, aggregation of the nuclei occurs. A high chloride concentration in solution favours the nucleation, promoting flat nuclei and star-shaped deposits. The species responsible for this behaviour are proposed to be chloro-cobalt complexes that adsorb on the crystallites, hindering the growth in some directions.