Adsorbate-Induced Surface Stress Measurements: A New Method for Monitoring in-Situ Surface Reactions

A new method to investigate in-situ catalytic reactions on single-crystal surfaces is introduced. The real-time technique of measuring the adsorbate-induced surface stress has been applied to the oxidation reaction of CO on Pt (111). The adsorption of each of the reactants, CO and oxygen, on Pt (111) induces a compressive stress which increases nonlinearly with the coverage. The stress-coverage dependence of CO and oxygen is explained by an ansatz, which considers the net charge transfer for an isolated adsorbate atom and the contribution of the wave-function overlap of adjacent atoms to the induced surface stress. The adsorbate-induced change of the total surface stress which is obtained during the surface reaction as a function of the time, is well reproduced by a Monte-Carlo simulation which regards the CO diffusion as well as the activation energy for the Langmuir-Hinshelwood reaction.