Growth forms, overpotential dependence

The dependence of growth forms on overpotentials originates from the potential dependence of nucleation and growth processes. Competition between nucleation... 

The dependence of growth forms on overpotentials originates from the potential dependence of nucleation and growth processes. Competition between nucleation and growth processes is strongly influenced by the potential of the cathode. Thus, major factors determining growth forms are as follows ... 

Moller etal. [462] have performed in situ STM observations of Ni electrodeposition on reconstructed Au(lll) electrodes. Ni nucleation proceeded in three distinct potential-dependent steps. The same group of researchers [463] has studied electrodeposition and electrodissolution of Ni on Au(lOO) electrodes. Pronounced differences were observed for the nucleation and submonolayer growth on the reconstructed and unreconstructed surfaces. On perfectly reconstructed Au(lOO), the formation of Ni islands started at overpotentials significantly higher (rj > 100 mV) than on unreconstructed surface (rj > 40 mV), where Ni monolayer islands were formed. Dissolution of the Ni film exhibited better monolayer stability in comparison to the multilayer deposit. 

Nucleation and the early stages of phase growth were discussed briefly in Chapter 1. It was noted that nucleation was always an improbable event and is achieved at an electrode surface by the application of a large overpotential. The density of nucleation is dependent on the plating bath and is extremely sensitive to the electrode potential (therefore also, of course, the current density). The growth of the nuclei once formed occurs quite rapidly at comparatively low overpotentials, and in a constant-current situation the potential will decrease substantially once nucleation has occurred. 

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