Adsorption of oxygen on Ag(110) studied by high resolution ELS and TPD

Abstract Adsorption of oxygen on Ag(110) has been studied by high resolution electron energy loss spectroscopy (ELS) and temperature programmed desorption (TPD) in the temperature range from − 160°C to 310°C. At − 160°C oxygen is absorbed as a diatomic species. The low vibrational frequency of the O-O stretch vibration is explained in terms of charge transfer from the metal into the π ∗ antibonding orbital and donation from the π bonding orbital to the metal. A tentative model is presented, according to which the molecule is adsorbed in the grooves of the (110) surface with its axis parallel to the surface. It is explicitly shown that this diatomic species is the precursor for dissociative adsorption of oxygen at temperatures above − 100°C. Upon dissociation part of the diatomic species is desorbed. Between − 100°C and + 310°C a single type of adsorbed atomic oxygen is observed which is desorbed at 310°C. Above 150°C adsorbed atomic oxygen also diffuses to subsurface sites. Below 450°C subsurface oxygen neither desorbs nor diffuses into the bulk, although it does exchange with adsorbed atomic oxygen at a temperature below 310°C. Therefore, both forms of atomic oxygen coexist at temperatures at which ethylene epoxidation occurs.

[1]  K. Crowe,et al.  7.7 m Bent Crystal Spectrometer at the 184 Inch Cyclotron , 1967 .

[2]  H. Voge,et al.  Catalytic Oxidation of Olefins , 1967 .

[3]  W. Sachtler.  THE MECHANISM OF THE CATALYTIC OXIDATION OF SOME ORGANIC MOLECULES , 1971 .

[4]  J. Rousseau,et al.  Relationship between vibrational states of O-Ni systems and their superficial structure on (100) face of nickel single crystal , 1977 .

[5]  G. Schulz,et al.  Resonances in Electron Impact on Diatomic Molecules , 1973 .

[6]  H. Engelhardt,et al.  Adsorption of oxygen on silver single crystal surfaces , 1976 .

[7]  R. Madix.  The application of flash desorption spectroscopy to chemical reactions on surfaces: Temperature programmed reaction spectroscopy , 1978 .

[8]  J. Valentine.  Dioxygen ligand in mononuclear Group VIII transition metal complexes , 1973 .

[9]  B. Feuerbacher,et al.  Infrared vibration spectroscopy of molecular adsorbates on tungsten using reflection inelastic electron scattering , 1977 .

[10]  G. Fisher,et al.  Oxygen interactions with the Pt(111) surface , 1980 .

[11]  S. Andersson.  Surface vibrations of oxygen and sulphur in the p(2 × 2) and c(2 × 2) structures on Ni(100) , 1979 .

[12]  G. Somorjai,et al.  The stability and structure of high miller index platinum crystal surfaces in vacuum and in the presence of adsorbed carbon and oxygen , 1977 .

[13]  L. Vaska.  Dioxygen-metal complexes: toward a unified view , 1976 .

[14]  F. Iberl,et al.  Oxygen adsorption on (110) silver , 1975 .

[15]  O. Gijzeman,et al.  Ellipsometry-LEED study of oxygen adsorption and the carbon monoxide- oxygen interaction on Ag(110) , 1978 .

[16]  G. Rovida,et al.  Chemisorption of oxygen on the silver (110) surface , 1975 .

[17]  D. P. Woodruff,et al.  Temperature dependent peaks in secondary electron emission spectra , 1973 .

[18]  C. Kuyatt,et al.  Electron Monochromator Design , 1967 .