Electrodeposition of Zinc on Glassy Carbon from ZnCl2 and ZnBr2 Electrolytes

Abstract

The initial stages of the electrocrystallization of zinc from and on glassy carbon has been investigated using cyclic voltammetry, the potential step method, and scanning electron microscopy. Particular care was taken to ensure electrolyte purity and to eliminate resistance effects in the measurements. The nucleation overvoltage in was ∼ 17 and ∼ 12 mV in . In , the current transients from the potential step measurements could be fitted to a simple model that assumes instantaneous nucleation followed by growth of three dimensional centers under kinetic control. A similar mechanism is operative for at low overvoltages. At higher overvoltages, the current transient is governed by mixed kinetic and diffusion control and cannot be fitted to a simple model. The lower nucleation overvoltage and the faster kinetics in is correlated with the lower stability constants for the zinc bromide complexes. Erroneous results are obtained when resistance effects are not accounted for.