The adsorption and reaction of H2O with adsorbed oxygen atoms on Ag(110) was examined by UPS. In agreement with previous EELS results, H2O formed multilayers of ice upon adsorption at 140 K. The ice layers could be easily distinguished from monolayer coverages of chemisorbed H2O (present above 160 K) by UPS. The ice layers produced (1) strong attenuation of the emission from the Ag d-bands, (2) a nearly 2 eV shift of H2O valence levels to higher binding energy and (3) strong attenuation of emission from the H2O 3a1 orbital. H2O was observed to react stoichiometrically with O(a) above 250 K to produce a pure layer of adsorbed hydroxyl species. The UPS spectra for these species exhibited features at ?5.8 and ?8.7 eV, as well as strong features above the d-bands. These spectra were compared with those for OH(a) on other surfaces, and the difficulties of identifying OH by UPS due to contamination by excess H2O are discussed. 相似文献
A kinetic study of D2 formation from HCOOD decomposition on Ni(110) (2 × 1)C was performed using the flash desorption technique. The surface structure and surface composition were monitored by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). Flash curves were obtained using initial coverage and heating rate variations. D2 formation exhibited a single second-order rate-determining step. Three different techniques were employed in obtaining the activation energy, two of which did not require the assumption of reaction order. Using an average value of 12.6 kcal/mole for the activation energy the pre-exponential factor was calculated to be 2.7 × 10?4 cm2 molecules?1 sec?1. Good agreement was achieved with the theoretically generated second-order flash curves only up to the peak temperature. The discrepancy on the high temperature side was explained using the model proposed by Clavenna and Schmidt utilizing a coverage dependent pre-exponential factor. 相似文献
The Midas touch : The low‐temperature transformation of methanol to methyl formate, formaldehyde, and formic acid is promoted by atomic oxygen adsorbed on metallic gold (see picture). The reactions occur with O‐containing Au nanoparticles formed on Au(111) upon oxidation with ozone at 200 K; the facile esterification to methyl formate occurs well below room temperature.
