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-crys tal surfaces is introduced. The real-time technique of measuring the a dsorbate-induced surface stress has been applied to the oxidation reac tion of CO on Pt(111). The adsorption of each of the reactants, CO and oxygen, on Pt(111) induces a compressive stress which increases nonli nearly with the coverage. The stress-coverage dependence of CO and oxy gen is explained by an ansatz, which considers the net charge transfer for an isolated adsorbate atom and the contribution of the wave-funct ion overlap of adjacent atoms to the induced surface stress. The adsor bate-induced change of the total surface stress which is obtained duri ng 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.