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O: Fachverband Oberflächenphysik

O 30: Mini-Symposium: Electrified solid-liquid interfaces I

O 30.1: Hauptvortrag

Dienstag, 2. März 2021, 10:35–11:10, R1

A Theoretical Framework for Investigating Electrochemical Reactions — •Wolfgang Schmickler — Institut für Theoretische Chemie, Universität Ulm, Deutschland

Electrochemical reactions take place at the interface between an electronic and an ionic conductor. Here we consider the most important case, a metal in contact with an electrolyte solution. The challenge is to treat electrocatalytic reaction, in which either the initial of the final state of the reaction is adsorbed on the electrode surface.

Consider the deposition of a silver ion on a silver electrode as an example. In the initial state, the 4s orbital is empty and the ion has a solvation energy of -5.1 eV. To get deposited, the ion has to approach the electrode, losing a part of its solvation energy. A thermal fluctuation takes the valence orbital, which is broadened by the interaction with the electrode, to the Fermi level. The ion takes up an electron, loses the solvation energy, and gains the energy of ionization, and the sublimation energy of silver; the potential drop between the solution and the electrode surface enters into the energy required to approach the electrode. Obviously, a good theory must treat all components of the interface, metal and solution, with the same atomic detail.

For this purpose we have developed a framework based on a model Hamiltonian, which combines ideas from Marcus theory, Anderson-Newns theory, Green's function techniques with our own ideas. The detailed form of the Hamiltonian depends on the reaction under consideration. We consider a few examples, and will how to obtain the parameters from DFT and molecular dynamics.