A Voltammetric Study Of The Underpotential Deposition Of Cobalt Onto A Glassy Carbon Electrode

We have carried out an electrochemical study of the underpotential deposition of cobalt onto glassy carbon electrode (GCE) from an aqueous 10-2 M CoClO4, 1M NH4CI (pH 4.5) solution by the voltammetric techniques (cyclic, linear and rotating disk electrode voltammetry). The analysis of the experimental data clearly showed the presence of an underpotential deposition (UPD) process of cobalt onto GCE that started at -0.160 V vs Ag/AgCl (KCl sat.). Both, the linear plots of the density current peak versus the scan potential rate and the limit density current versus the rotation rate also suggested that the UPD process of cobalt onto GCE was diffusional-controlled. The voltammetric studies suggested the existence of at least two phases of cobalt deposited in UPD conditions. The formation of the first phase was favored in the [-0.200 - -0.370] V range and when the thickness of the diffusional layer decreased, while the second one was favored in the [-0.380 - -0.550] V range.