TY - JOUR
T1 - Influence of the coordination sphere on the mechanism of cobalt nucleation onto glassy carbon
AU - Palomar-Pardavé, Manuel
AU - González, Ignacio
AU - Soto, Ana B.
AU - Arce, Elsa M.
N1 - Funding Information:
This work was partially financed by the Consejo Nacional de Ciencia y Tecnologia (projects: L0081-E9608 and 1779P-A9507) of México and by the project JICA-IPN (DEPI-962805). Two of us (Manuel Palomar-Pardavé and A.B. Soto) also wish to acknowledge CONACYT for the research fellowship granted us for carrying out this work. The authors are also indebted to Dr. A. Morales-Pérez for fruitful discussions.
PY - 1998/2/10
Y1 - 1998/2/10
N2 - Electrolytic phase formation of cobalt onto a glassy carbon electrode (GCE) was investigated using linear sweep voltammetry and the potential step technique in aqueous 10-2 M CoCl2 + 1 M NH4Cl at pH 4.6 and 9.5. Thermodynamic, voltammetric and spectrophotometric analysis of the solutions showed that the predominant chemical species of Co(II) in solution were the Co(H2O)2+6 ion at pH 4.6 and the Co(NH3)2+5 complex at pH 9.5. Voltammetric analysis showed that the experimental equilibrium potential of the Co(NH3)2+5/Co(0) system was more negative than the Co(H2O)2+6/Co(0) couple. However the electrocrystallization overpotential for cobalt deposition on GCE from the aquo complex was higher than for the amine complex. Analysis of the current-time transients obtained at each pH, indicated that distinct mechanisms of nucleation are involved during the early stages of cobalt deposition. In the case of Co(H2O)2+6 reduction, the transients were described theoretically in terms of 3D nucleation with diffusion controlled growth. For cobalt deposition from the Co(NH3)2+5 species, the transients were explained by a combination of three different kinds of parallel nucleation processes, 2D progressive nucleation, 2D instantaneous nucleation and 3D progressive nucleation, each of which was limited by lattice incorporation of cobalt ad-atoms.
AB - Electrolytic phase formation of cobalt onto a glassy carbon electrode (GCE) was investigated using linear sweep voltammetry and the potential step technique in aqueous 10-2 M CoCl2 + 1 M NH4Cl at pH 4.6 and 9.5. Thermodynamic, voltammetric and spectrophotometric analysis of the solutions showed that the predominant chemical species of Co(II) in solution were the Co(H2O)2+6 ion at pH 4.6 and the Co(NH3)2+5 complex at pH 9.5. Voltammetric analysis showed that the experimental equilibrium potential of the Co(NH3)2+5/Co(0) system was more negative than the Co(H2O)2+6/Co(0) couple. However the electrocrystallization overpotential for cobalt deposition on GCE from the aquo complex was higher than for the amine complex. Analysis of the current-time transients obtained at each pH, indicated that distinct mechanisms of nucleation are involved during the early stages of cobalt deposition. In the case of Co(H2O)2+6 reduction, the transients were described theoretically in terms of 3D nucleation with diffusion controlled growth. For cobalt deposition from the Co(NH3)2+5 species, the transients were explained by a combination of three different kinds of parallel nucleation processes, 2D progressive nucleation, 2D instantaneous nucleation and 3D progressive nucleation, each of which was limited by lattice incorporation of cobalt ad-atoms.
KW - 2D electrocrystallization
KW - 3D electrocrystallization
KW - Amine cobalt complex
KW - Cobalt deposition
KW - Cobalt electrocrystallization
UR - http://www.scopus.com/inward/record.url?scp=0031996856&partnerID=8YFLogxK
U2 - 10.1016/S0022-0728(97)00496-8
DO - 10.1016/S0022-0728(97)00496-8
M3 - Artículo
SN - 1572-6657
VL - 443
SP - 125
EP - 136
JO - Journal of Electroanalytical Chemistry
JF - Journal of Electroanalytical Chemistry
IS - 1
ER -