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Adsorption and decomposition of HNCO on Cu(111) surface studied by Auger electron, electron energy loss and thermal desorption spectroscopy
A85 the reaction of CO with preadsorbed square-root
of the
oxygen
atom
oxygen atoms, the reaction rate was dependent upon the coverage, suggesting that oxygen atoms were adsorbed in
islands on this surface. The oxidation of preadsorbed CO was observed only when the initial CO concentrations were less than 0.5 monolayer (~(2 X 2) structure), suggesting that the dissociative adsorption of oxygen required adjacent four-fold surface sites. The activation energy calculated for the reaction of CO with preadsorbed oxygen was 31.4 kcal/mol. This value was 30 kcal/mol greater than the activation energy measured for the reaction of 02 with preadsorbed CO. Strong attractive interactions within the oxygen islands were at least partially responsible for this difference. The reaction kinetics in both cases changed dramatically below 300 K; this change is believed to be due to phase separation at the lower temperature.
Surface Science 104 (1981) 181-198 North-Holland Publishing Company ADSORPTION AND DECOMPOSITION OF HNCO ON Cu(ll1)
SURFACE
STUDIED BY AUGER ELECTRON, ELECTRON ENERGY LOSS AND THERMAL DESORPTION SPECTROSCOPY F. SOLYMOSI and J. KISS Reaction Kinetics Research Group, The University, P.O. Box 105, H-6701 Szeged, Hungary
Received 25 June 1980; accepted for publication 13 October 1980 No detectable adsorbed species were observed after exposure of HNCO to a clean Cu( 111) surface at 300 K. The presence of adsorbed oxygen, however, exerted a dramatic influence on the adsorptive properties of this surface and caused the dissociative adsorption of HNCO with concomitant release of water. The adsorption of HNCO at 300 K produced two new strong losses at 10.4 and 13.5 eV in electron energy loss spectra, which were not observed during the adsorption of either CO or atomic N. These loses can be attributed to surface NC0 on Cu( 111). The surface isocyanate was stable up to 400 K. The decomposition in the adsorbed phase began with the evolution of CO2. The desorption of nitrogen started at 700 K. Above 800 K, the formation of CzN2 was observed. The characteristics of the CO2 formation and the ratios of the products sensitively depended on the amount of preadsorbed oxygen. No HNCO was desorbed as such, and neither NC0 nor (NC0)2 were detected during the desorption. From the comparison of adsorption and desorption behaviours of HNCO, N, CO and CO2 on copper surfaces it was concluded that NC0 exists as such on a Cu(ll1) surface at 300 K. The interaction of HNCO with oxygen covered Cu(ll1) surface and the reactions of surface NC0 with adsorbed oxygen are discussed in detail.
Surface Science 104 (1981) 199-204 North-Holland Publishing Company MECHANISM FOR THE SELF-DIFFUSION
OF Au AND Ir ADATOMS
ON Pt( 110) SURFACE Stephen H. GAROFALINI Rutgers University, Department USA
and
of Ceramics, P.O. Box 909, Piscataway, New Jersey 08854,
of the
oxygen
atom
oxygen atoms, the reaction rate was dependent upon the coverage, suggesting that oxygen atoms were adsorbed in
islands on this surface. The oxidation of preadsorbed CO was observed only when the initial CO concentrations were less than 0.5 monolayer (~(2 X 2) structure), suggesting that the dissociative adsorption of oxygen required adjacent four-fold surface sites. The activation energy calculated for the reaction of CO with preadsorbed oxygen was 31.4 kcal/mol. This value was 30 kcal/mol greater than the activation energy measured for the reaction of 02 with preadsorbed CO. Strong attractive interactions within the oxygen islands were at least partially responsible for this difference. The reaction kinetics in both cases changed dramatically below 300 K; this change is believed to be due to phase separation at the lower temperature.
Surface Science 104 (1981) 181-198 North-Holland Publishing Company ADSORPTION AND DECOMPOSITION OF HNCO ON Cu(ll1)
SURFACE
STUDIED BY AUGER ELECTRON, ELECTRON ENERGY LOSS AND THERMAL DESORPTION SPECTROSCOPY F. SOLYMOSI and J. KISS Reaction Kinetics Research Group, The University, P.O. Box 105, H-6701 Szeged, Hungary
Received 25 June 1980; accepted for publication 13 October 1980 No detectable adsorbed species were observed after exposure of HNCO to a clean Cu( 111) surface at 300 K. The presence of adsorbed oxygen, however, exerted a dramatic influence on the adsorptive properties of this surface and caused the dissociative adsorption of HNCO with concomitant release of water. The adsorption of HNCO at 300 K produced two new strong losses at 10.4 and 13.5 eV in electron energy loss spectra, which were not observed during the adsorption of either CO or atomic N. These loses can be attributed to surface NC0 on Cu( 111). The surface isocyanate was stable up to 400 K. The decomposition in the adsorbed phase began with the evolution of CO2. The desorption of nitrogen started at 700 K. Above 800 K, the formation of CzN2 was observed. The characteristics of the CO2 formation and the ratios of the products sensitively depended on the amount of preadsorbed oxygen. No HNCO was desorbed as such, and neither NC0 nor (NC0)2 were detected during the desorption. From the comparison of adsorption and desorption behaviours of HNCO, N, CO and CO2 on copper surfaces it was concluded that NC0 exists as such on a Cu(ll1) surface at 300 K. The interaction of HNCO with oxygen covered Cu(ll1) surface and the reactions of surface NC0 with adsorbed oxygen are discussed in detail.
Surface Science 104 (1981) 199-204 North-Holland Publishing Company MECHANISM FOR THE SELF-DIFFUSION
OF Au AND Ir ADATOMS
ON Pt( 110) SURFACE Stephen H. GAROFALINI Rutgers University, Department USA
and
of Ceramics, P.O. Box 909, Piscataway, New Jersey 08854,