Electrochemical nucleation of metals

Kaveh Pour, Azar Midokht (1981) Electrochemical nucleation of metals. University of Southampton, Doctoral Thesis.

Abstract

A study has been made of the electrochemical nucleation of silver, mercury and copper from aqueous solutions over a wide range of concentrations and on different substrates. The potentiostatic current transients were recorded and analysed in order to obtain information on the mechanism of nucleation and growth. Simultaneously, microscopical observations were made so that the results obtained from the analysis of the electrochemical measurements could be confirmed. Electron scanning microscopy was also used to obtain a more certain description of the morphology of the crystallites and the condition of the substrate. Rates of nucleation were calculated and their dependence on overpotential was delineated in terms of classical and atomistic theories. From the application of the atomistic theory, the number of atoms in the critical nucleus was obtained. The effect of complexing agents on the kinetics of nucleation and crystal morphology has been investigated. The electrodeposition of metals on -platinum and carbon microelectrodes was studied in order to characterise unambiguously the magnitude of the current due to the growth of single nucleus. As a result, it was possible to analyse the current transients in terms of hemispherical diffusion. For higher concentrations of silver solutions, the currents were found to be controlled by the ohmic resistance of the silver solution. Open circuit potential measurements of nuclei deposited on microelectrodes have been carried out and an attempt was made to explain the disparities observed when the classical theory is used. Finally, measurements were made of the exchange current densities of the silver, mercury and copper in aqueous solutions.

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