Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 13: Solid-liquid interfaces

O 13.3: Talk

Monday, March 27, 2006, 15:30–15:45, WIL C207

Modeling electrocatalysis – electro-oxidation of Pt(111) — •Timo Jacob and Matthias Scheffler — Fritz-Haber Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany

Electrochemical reactions (such as in fuel cells) usually occur under conditions of finite temperature, pressure, and electrode potential, implying a very involved situation, possibly leading to novel surface materials. Especially the presence of an electrode potential, which results in the formation of an electric double-layer, affects the composition and structure of the electrode/electrolyte-interface.

Towards a more realistic treatment of electrocatalysis we developed an appropriate theory in which the electrode of the interface is assumed to be in contact with a bulk-electrode reservoir (at chemical potential µ_el) while the electrolyte is in contact with a bulk-electrolyte reservoir. Although we are in the process of simulating the entire electric-double layer self-consistently, the present approach already allows us to estimate the limites of the expected effects.

As a first application we studied the electro-oxidation of Pt(111) by calculating the p/T/φ-phase diagram. The obtained behavior, that positive electrode potentials stabilize higher oxygen coverages, is in qualitative agreement with cyclic-voltammetry experiments.