A study of the initial stages of the electrochemical deposition of lead and thalliam on copper
A study of the initial stages of the electrochemical deposition of lead and thalliam on copper
The underpotential deposition and the initial stages of overpotential deposition of thallium and lead onto polycrystalline and single crystal copper, and vitreous carbon electrodes have been investigated using conventional electrochemical techniques.Careful chemical polishing of the copper electrode surfaces was chosen to remove the distorted layers left by alumina polishing, while fine mechanical polishing was used to prepare the vitreous carbon electrode surface.The voltammetric behaviour of the polycrystalline copper electrodes was shown to be a composite of the various single crystal structures in its surface. NVoltammetry at single crystal electrodes showed that lead formed a single underpotential monolayer and thallium formed two monolayers. The process of monolayer deposition was dependent on substrate orientation and consisted basically of two stages: an initial adsorption process in which the favourable, high coordination, sites on the electrode surface were occupied, followed by a phase transformation and crystal growth process until a complete layer was formed.The single monolayer of lead on Cu(110) and the first monolayers of thallium on all the orientations of Cu were shown to be close-packed layers. The monolayers of lead on Cu(ill) and (100) had the closest-packed epitaxial structure. The close-packed, non-registered layers were presuued to be partly distorted by the underlying substrate structure. In the case of thallium, these distortion effects were also felt in the formation of the second layer. It was found that the UPD process examined involved 2D phase transformations of first order or of higher order. This was established by analysis of the growth transients at constant potential which showed behaviour characteristic of nucleation and growth processes. The higher order processes gave continuous monolayer density changes. The effects of metal ion and anion concentration on the UPD peak potentials were investigated. These were interpreted in terms of the changes in the electronegativities of the substrate and underpotential layers as the result of the changing electrode potential. The monolayer formation was found to be, in the case of copper substrates, an essential precursor to thicker deposits; its influence on the initiation of the overpotential deposition and its growth mechanism, was shown to be very significant. Repetitive underpotential deposition on vitreous carbon was found to bring about substrate surface reconstruction which profoundly influenced the nucleation and the growth mechanism for bulk lead deposition.
University of Southampton
1978
Jovicevic, Jovan N
(1978)
A study of the initial stages of the electrochemical deposition of lead and thalliam on copper.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The underpotential deposition and the initial stages of overpotential deposition of thallium and lead onto polycrystalline and single crystal copper, and vitreous carbon electrodes have been investigated using conventional electrochemical techniques.Careful chemical polishing of the copper electrode surfaces was chosen to remove the distorted layers left by alumina polishing, while fine mechanical polishing was used to prepare the vitreous carbon electrode surface.The voltammetric behaviour of the polycrystalline copper electrodes was shown to be a composite of the various single crystal structures in its surface. NVoltammetry at single crystal electrodes showed that lead formed a single underpotential monolayer and thallium formed two monolayers. The process of monolayer deposition was dependent on substrate orientation and consisted basically of two stages: an initial adsorption process in which the favourable, high coordination, sites on the electrode surface were occupied, followed by a phase transformation and crystal growth process until a complete layer was formed.The single monolayer of lead on Cu(110) and the first monolayers of thallium on all the orientations of Cu were shown to be close-packed layers. The monolayers of lead on Cu(ill) and (100) had the closest-packed epitaxial structure. The close-packed, non-registered layers were presuued to be partly distorted by the underlying substrate structure. In the case of thallium, these distortion effects were also felt in the formation of the second layer. It was found that the UPD process examined involved 2D phase transformations of first order or of higher order. This was established by analysis of the growth transients at constant potential which showed behaviour characteristic of nucleation and growth processes. The higher order processes gave continuous monolayer density changes. The effects of metal ion and anion concentration on the UPD peak potentials were investigated. These were interpreted in terms of the changes in the electronegativities of the substrate and underpotential layers as the result of the changing electrode potential. The monolayer formation was found to be, in the case of copper substrates, an essential precursor to thicker deposits; its influence on the initiation of the overpotential deposition and its growth mechanism, was shown to be very significant. Repetitive underpotential deposition on vitreous carbon was found to bring about substrate surface reconstruction which profoundly influenced the nucleation and the growth mechanism for bulk lead deposition.
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Published date: 1978
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Local EPrints ID: 459748
URI: http://eprints.soton.ac.uk/id/eprint/459748
PURE UUID: f9044cb1-7a37-4b5e-8e9a-99967f2d0552
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Date deposited: 04 Jul 2022 17:17
Last modified: 04 Jul 2022 17:17
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Jovan N Jovicevic
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