Electrochemical Nucleation and Growth of Cobalt from Methanesulfonic Acid Electrolyte

Abstract

Electrochemical nucleation and growth of cobalt onto glassy carbon electrode (GCE) from methanesulfonic acid (MSA) electrolyte was investigated, the influence of pH and cobalt concentration on the electrocrystallization mechanism was also examined. Cyclic voltammetry experiments indicate a pH and cobalt concentration dependence of the onset potential and a deposit phase change with decreasing pH was also noted. From analysis of current transients, the diffusion coefficient of cobalt ion was estimated as 1.89 × 10 -5 cm 2 s -1 . The electrocrystallization mechanism for 0.6 mol/L Co 2+ follows the instantaneous nucleation with kinetic controlled growth and is independent of the bath pH while the mechanism for 0.2 mol/L Co 2+ follows the progressive nucleation with diffusion controlled growth at pH = 2.0 and then goes to instantaneous nucleation with kinetic controlled growth at pH = 1.5 and exhibits a process of progressive nucleation with kinetic controlled growth with lower pH of 1.0.

Analysis of the electrodeposition process of Fe–Mn films from sulfate electrolytes

“…For the case only with (NH 4 ) 2 SO 4 , the current reaches an approximately steady state value immediately after the initial peak. The fluctuations in the current can be attributed to the release of bubbles resulting from the hydrogen evolution reaction [22]. The behavior is very similar for several speeds, but the value of the almost steady current increases with the increase of ω.…”

“…The more detailed three-dimensional approach has not a simple analytical solution and has been recently reviewed [10,11]. A common approach is based on the growth of planar diffusion zones [18][19][20][21][22][23][29][30][31], and is called standard model or Scharifker-Hills model [8,10,11,20]. This last model has the advantage to present a single analytical expression for the time (t) dependence of the current density, represented in equation (10) (current density 'i' in modulus).…”

“…Here we have opted to compare the SH fits with the Isaev et al approaches (IGZ) considering the known parameters in each case. In the IGZ model [9][10][11]22] the growth follows the law of hemispherical diffusion and not planar diffusion zones as in the SH model. Consequently, there is no a single expression like equation (10) to be fitted and the transient curve is calculated recursively.…”

“…Equation in table 2 were used, reducing the free parameters to A and N o . In order to take the hydrogen evolution into account, a constant term was added to equation (10), in the same sense as it has been done in recent works [21,22]. This is also an approximation since the results of figure 6(a) show the contribution from hydrogen evolution is not constant at the beginning of the deposition, but tends to a steady state after about 5 s. For the IGZ model, the curves were generated using the software Wolfram Mathematica considering the approach presented in references [10,11] (refer to supplementary material for an example of Mathematica file with the calculations).…”

“…In order to investigate these aspects, we have compared our experimental results with the models from Isaev et al [9][10][11] and Scharifker et al [18][19][20] for current transients during the deposition. Both these models have been used recently in the analysis of single metal electrodeposition [21,22], as well as for alloys deposition [23]. The model for current transients of alloys is, in fact, an extended approach for diffusion controlled electrodeposition introducing the concept of 'apparent' parameters which take into account bimetallic phases [5].…”