Underpotential deposition of metals and work function differences

The electrolytic deposition of metal atoms onto foreign metal substrates at underpotentials has been studied in aqueous and non-aqueous solutions. It is shown, that the potential difference between monolayer and bulk deposition is closely related to the difference in the work functions of substrate and deposit, causing a partial charge of the adatoms. The ionic contribution to the chemical bond, arising from this partial electron transfer, can account for the favourable deposition of the first monolayer. A formula is given which allows the prediction of the amount of underpotential shift from differences in work function. This is explained in analogy to Pauling's treatment of the chemical bond between atoms of different electronegativity.