Facile NOx interconversion over preoxidized Ag(111)

X-ray photoelectron spectroscopy and density functional theory calculations are used to investigate NO adsorption at low (100 K) and room temperature (RT) over preoxidized Ag(111). At 100 K, the data indicates presence of NO and N2O2, with little or no nitrite/nitrate formation. This is consistent with the calculated surface core level shifts and the pronounced barrier for nitrite formation. At RT, the recorded spectra indicate a complex interconversion between adsorbed species with an initial formation of a p(4 x 4) nitrate overlayer. With increasing NO pressure, the experimental results are best rationalized by partial nitrate decomposition into nitrites and subsequent NO physisorption, which leads to the formation of N2O3-like species

Carbonate formation on p(4 x 4)-O/Ag(111)

High-resolution core-level spectroscopy and density-functional theory calculations have been used to investigate CO adsorption on the p(4 x 4) structure of oxidized Ag(111). CO adsorption with subsequent carbonate formation was observed at 100 K. The experimental results are consistent with calculations that reveal low activation barriers to form CO2 and CO32- from adsorbed CO. On the basis of a good match between calculated and experimental shifts in the Ag 3d and O 1s core-level binding energies, a model for a monolayer of carbonates on p(4 x 4)-O/Ag(111) is proposed

Oxidation at the Subnanometer Scale

Metals are commonly oxidized under ambient conditions. Although bulk oxidation has received considerable attention, far less is known about oxidation at the subnanometer scale. This is unfortunate, as metal particles used in heterogeneous catalysis typically range from subnanometer to some nanometers. Here, density functional theory calculations are used to explore oxidation of gas-phase transition metal clusters in the range from the dimer to the dodecamer. Comparisons with the corresponding bulk systems uncover that the decomposition temperature of stoichiometrically oxidized clusters may be lower than for the bulk. Despite pronounced variations in ground state geometries, oxidized clusters closely mimic energetic trends across the periodic table valid for bulk systems

High-Coverage Oxygen-Induced Surface Structures on Ag(111)

Surface structures formed by exposing Ag(111) to atomic oxygen have been studied by X-ray photoelectron spectroscopy, scanning tunneling microscopy, and density functional theory calculations. From the combination of the experimental and theoretical results, a model is proposed for the 0.5 ML oxygen coverage with a c(4 x 8) periodicity. Moreover, we find that a bulk-like Ag2O phase starts to form at coverages above 0.5 ML