ADSORPTION - DESORPTION-KINETICS OF CO FROM CLEAN AND SULFUR COVERED RU(001)

The total uptake of CO, its adsorption kinetics and its desorption kinetics from clean and partially sulfur covered surfaces of the basal plane of ruthenium have been investigated. The method of desorption rate isotherms applied to the CO flash desorption spectra from these surfaces was used to evaluate the coverage dependence of the binding energy of CO as well as the effect of various levels of sulfur on this binding energy. Below a total surface concentration of 1 adsorbate atom per 3 surface Ru atoms, the binding energy and sticking probability of CO on the clean and sulfur covered surfaces are the same. Above this concentration of total adsorbates, the adsorption kinetics is the same on all surfaces studied, the binding energy decreases linearly with CO coverage while the magnitude of the decrease increases with sulfur coverage. The total uptake of CO depends on the amount of preadsorbed sulfur. At low coverages of sulfur, total CO uptake is effected by the excluded volume of sulfur. At higher coverages of sulfur (approaching 1 2 the maximum sulfur concentration on the clean surface) the site requirements of sulfur limits the amount of CO that can adsorb on the remaining surface, to the quantity of 1 adsorbate atom per 2 Ru atoms. © 1979.