Quantum Chemistry of Electrode Processes. I. General Relations for Electron Exchange between Electrode and Electroactive Species under Equilibrium and Nonequilibrium Conditions

摘要

It is assumed in this paper that at the electrodemdash;solution interface there is molecular order of the electroactive species resembling solidhyphen;state order. Specifically, it is assumed that next to the electrode is a layer of adsorbed neutral solvent molecules which are also ligands coordinated to the ions found in the interface. The mechanism of electron transfer from the electrode to the ion or the reverse from the ion to the electrode is assumed initially to involve a transition from either the electrode or the ion to the solvent molecule. This is followed by a transition of the electron from the solvent molecule to either the ion or the electrode. The two transitions involved in the net transfer of an electron across the interface are considered analogous to the chargehyphen;transfer mechanism of spectroscopy. The wavefunctions representing the system at the interface are then of the same form as the chargehyphen;transfer wavefunctions given by Mulliken.By considering the radiationless transition probabilities for the electron transitions in the interface system at the electrode, it is found that the usual current expressions result. By imposing the condition of zero net current at equilibrium the Nernst equation results. By further considering the polarization of the electrode under nonequilibrium conditions as a perturbation of the energy levels of the system, it is found that with the proper identification of terms the current expression for the polarized electrode results.