Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 67: Symposium: The Solid-Liquid Interface: A Challenge for Theoreticians II
O 67.4: Vortrag
Freitag, 30. März 2007, 11:30–11:45, H38
d-Band Catalysis in Electrochemistry — •Sonja Bartenschlager1, Wolfgang Schmickler1, and Elizabeth Santos2 — 1Universität Ulm, Institut für Theoretische Chemie, Albert-Einstein-Allee 11, 89069 Ulm — 2Zentrum für Sonnenenergie und Wasserstoff-Forschung, Helmholtzstr. 8, 89081 Ulm
Understanding the mechanism of electrocatalysis is of primary importance for the development of efficient fuel cells. We present the first theory for electrochemical electron transfer reaction that can account for specific catalytic effects caused by the interaction of the reactants with the d-band of a metal electrode. It is based on a model Hamiltonian that combines elements of the Anderson-Newns theory with tight binding and with the Marcus theory.
We have applied this model to the breaking of a bond in a diatomic molecule; this is a particularly important case, since generally bond breaking requires a strong catalytic effect of the electrode. Specifically, we have performed calculations based on a simple, semi-elliptic form of the d-band. In this way, we were able to demonstrate and understand a number of qualitative effects: the change in the density of states as the reaction proceeds and the system passes the saddle point; the importance of a high density of d-band states near the Fermi level, which interact with the anti-bonding orbital as it passes the Fermi level; the loss of symmetry between the anodic and cathodic direction; the decrease in the energy of activation with increasing interaction, which in extreme cases can result in dissociative adsorption without barrier.