Electrochemical and AFM study of Zn electrodeposition in the presence of benzylideneacetone in a chloride-based acidic bath

The influence of benzylideneacetone (BDA) on the mechanism of zinc deposition and nucleation was studied by voltammetry, chronoamperometry and atomic force microscopy (AFM). The addition of BDA to the electrolyte solution partially inhibited (97%) the reduction of zinc at the potential E = -1.15 vs SCE/V, giving rise to an increase in the overpotential for the discharge of the metal ion. This leads to the existence of two reduction processes with different energies that involve the same species, ZnCl42-. Analysis of chronoamperograms obtained in the absence and presence of BDA indicates that distinct nucleation mechanisms are involved during the initial stages of Zn deposition. In the absence of BDA, the transients are consistent with the model of 3D diffusion-controlled nucleation. In the presence of BDA, the transients exhibit a more complex form involving two growth processes. The first process, which occurs at short times, is explained in terms of a combination of three simultaneous nucleation processes: 2D progressive, 2D instantaneous, and 3D progressive nucleation, each limited by the incorporation of adatoms. The second process, which occurs at longer times, involves the three processes that occur at short times in conjunction with a principal contribution from a diffusion-controlled 3D nucleation mechanism. AFM imaging shows that the morphology of the deposited zinc depends on the applied electrode potential.