ON THE MECHANISM OF ELECTROCHEMICAL ION TRANSFER-REACTIONS

The Gibbs energy curve experienced by an ion approaching the surface o f a metal electrode is investigated by molecular dynamics using the I- ion approaching a platinum electrode in an aqueous solution as an exa mple. The maximum of the potential energy curve is determined by the p artial desolvation of the ion before it is adsorbed. Electron exchange with the electrode does not occur at the maximum of the potential ene rgy curve, but on the descending branch where the ion approaches the s urface. A surface charge density on the electrode surface changes the potential energy curve both through the action of the resulting electr ic field and by changing the structure of the solvent near the surface . It is argued that ion transfer reactions differ in fundamental aspec ts from electron transfer reactions and cannot be interpreted in terms of the Marcus theory.