An X-ray photoelectron spectroscopy study of the influence of hydrogen on the oxygen-silver interaction

Hydrogen treatment of a pure silver catalyst before adsorption of oxygen influences the position and form of the O(1s) peak of the X-ray photoelectron spectra. It is possible that both the formation of sub-surface OH groups and an increase in the concentration of sub-surface oxygen, found to be of importance in earlier work, are responsible for this effect. Furthermore, when oxygen adsorption is carried out with extremely high exposures and at elevated temperature, pronounced differences occur in spectra obtained at temperatures between 298 and 723 K as compared with the results of ultrahigh vacuum studies reported in the literature. These differences are again most probably caused by the presence of the sub-surface oxygen in the present study.