Chemisorption

About: Chemisorption is a research topic. Over the lifetime, 16298 publications have been published within this topic receiving 554989 citations.

XPS and ISS studies on the interaction of H2S with polycrystalline Cu, Cu2O and CuO surfaces

Abstract: The first steps of H 2 S adsorption have been studied on polycrystalline copper samples, which are more relevant to industrial copper samples than to single-crystal surfaces. The tools for characterization are ultrahigh vacuum spectroscopic methods, such as x-ray photoelectron and ion scattering spectroscopies. The H 2 S adsorption on metallic copper and on the corresponding Cu 2 O and CuO oxides is dissociative and highly dependent on the chemical nature of the exposed surface rather than on the temperature, from room temperature up to 623 K. In our conditions, Cu° sulphidation deals with the top Cu° layer whereas two to three oxide surface monolayers are modified at H 2 S saturation. The results on oxides are interpreted by an oxygen/sulphur replacement mechanism following the dissociative adsorption. Contaminated copper surfaces by phenanthrene or H 2 O treatments are hardly sulphided. As far as surface reactivity is concerned, the adsorbed sulphide species have been shown to be quite strongly bound to the different surface states tested in this work: only oxidative treatments induce desorbing products at 623 K

X-ray photoemission spectroscopy study of UV/ozone oxidation of Au under ultrahigh vacuum conditions

Abstract: (111) textured Au films were oxidized under UHV conditions by exposing them to UV radiation and ozone. The Au films were characterized by x-ray photoelectron spectroscopy. The gold surface becomes heterogeneous upon oxidation: approximately 0.8 monolayer (ML) of the adsorbed oxygen is present as chemisorbed species. The rest of the adsorbed oxygen forms, on the average, a few ML thick gold oxide with a stoichiometry close to Au2O3. Both the oxide and the chemisorbed oxygen disappear slowly when heated to 150 °C. During isothermal decomposition at 200 °C, the oxide is transformed to chemisorbed oxygen prior to desorption. Both the chemisorbed oxygen and the gold oxide can be removed by rinsing with water. The surface is hydrophilic after the rinse. When contaminated gold films are exposed to UV/ozone, impurity oxides appear at higher binding energies than the binding energies of oxygen on clean gold samples. The impurity oxides are thermally much more stable than Au2O3.

Precursor state in the chemisorption of CO on supported palladium clusters

Abstract: It is demonstrated that physisorption of CO molecules on a MgO (100) surface, supporting epitaxially grown Pd particles, acts as a precursor state for CO chemisorption on the particles. The adsorption rate of CO on the Pd particles is measured, at zero coverage by a molecular beam technique, as a function of the substrate temperature and for different particle sizes. A kinetic model describing the adsorption, desorption, diffusion, and capture by the clusters of CO molecules is given. Comparison with the experimental data gives the adsorption probability: 0.5±0.05 and the saddle energy for surface diffusion: 0.25±0.05 eV of CO molecules on MgO.