The underpotential deposition (UPD) of metals on defined metal single crystal surfaces represents a relatively new field of investigations. In this paper, the latest theoretical and experimental results in this topic are summarized with respect to the thermodynamic, kinetic and structural properties of UPD submonolayers and monolayers. Furthermore, surface reconstruction phenomena, alloy formation, interrelation between UPD and electrocrystallization, electrocatalytic effects caused by UPD, and optical results are discussed. It is mentioned that UPD represents a special case for initial steps in phase formation processes in heterogeneous systems.

Underpotential Metal Deposition on Single Crystal Surfaces

Underpotential deposition of lead on polycrystalline and single-crystal gold surfaces

The underpotential deposition of metals on foreign metal substrates has been reviewed, but this term is used in a wider sense in this monograph All the redox processes resulting in adsorbed metal atoms on foreign metal substrates are included in this term Based on the source of electrons taking part in the underpotential deposition, the classification of the processes leading to adsorbed metal atoms is also given

Underpotential deposition of metals on foreign metal substrates

Electrocrystallization phenomena are considered and basic thermodynamic and kinetic concepts related to the electrochemical nucleation and growth are defined and discussed in details. Theoretical and experimental findings related to the stationary and non-stationary nucleation kinetics, growth of single two-and three-dimensional crystals as well as underpotential deposition phenomena and spatial distribution of clusters are reviewed and the reader is referred to suitable sources of reliable information on the most important subjects concerned.

Electrocrystallization: Nucleation and growth of nano-clusters on solid surfaces

Thermodynamics and kinetics of underpotential deposition of metal monolayers on polycrystalline substrates

The structures of the two-dimensional layers formed in the underpotential deposition of lead onto carefully prepared single crystals of copper are shown to depend upon the substrate orientation for (111), (100) and (110) surfaces. Nucleative growth processes are observed for first order and for higher order phase transitions. Comparison is made with the behaviour observed on silver substrates and the differences are ascribed to the change in atomic radius and in eletronegativity. Formation of the underpotential layer is shown to be a necessary precursor to overpotential deposition, the mechanism of which is markedly dependent on substrate orientation.

Brian Thomas

Papers

Phase formation in the underpotential deposition of metals