The electrocrystallization of nickel was studied on a platinum ultramicroelectrode (UME). The behaviour of the current transients pointed to an instantaneous nucleation process under kinetic control. The application of Abyaneh's model showed that nuclei grow in a spherical cap geometry with different values for both rate constants in the parallel and perpendicular directions. The parallel rate constants for nuclei growth varied from 5.97 x 10-7 to 1.92 x 10-7 mol cm-2 s-1 by increasing the step potential from -0.57 to -0.63 V, while the perpendicular rate constant remained constant around 1.44 x 10-7 mol cm-2 s-1. The relationships between these two constants give the contact angles of the crystallites, whose values also increased with potential from 27.5 to 87.6 degrees. Finally, the number of nuclei formed on the surface increased with potential from 0.43 x 10(7) to 379.09 x 10(7) cm-2.
electrocrystallization; spherical caps; ultramicroelectrodes; nickel
