Modeling Electrocatalysis -- Electro-oxidation of Pt(111)

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 {\it bulk-electrode} reservoir (at chemical potential $\mu_{\mathrm{el}}$) while the electrolyte is in contact with a {\it 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 $p/T/\phi$-phase diagram. The obtained behavior, that positive electrode potentials stabilize higher oxygen coverages, is in qualitative agreement with cyclic-voltammetry experiments.