Underpotential deposition of metals – Progress and prospects in modelling

Underpotential deposition (UPD) of metals is analysed from the perspective of phenomenological and statistical thermodynamic considerations; the parameters influencing the UPD shift have been quantitatively indicated using a general formalism. The manner in which the macroscopic properties pertaining to the depositing ions and solvent dipoles and the nature of the metallic substrate influence the UPD process are highlighted; earlier correlations of the UPD shift with the work function differences are rationalised. Anion-induced phase transitions which manifest as sharp peaks in experimental cyclic voltammograms are discussed using statistical thermodynamic models.