High resolution electron energy loss investigations of the adsorption of NO on the clean and oxygen precovered Ru(001) surface

Conrad, H.; Scala, R.; Stenzel, W.; Unwin, R.

doi:10.1016/0039-6028(84)90762-3

Cited by 69 publications

(28 citation statements)

References 31 publications

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“…Based on the observed spectra shown in figure 5.2, we believe the top-site NO either desorbs or shifts to bridge-site NO instead of dissociating; however, the bridge-site NO is the major contributor to the dissociation of NO to atomic oxygen and nitrogen in the temperature range of 350-480 K. Similar findings have also been reported on other metal surfaces, such as Ru(OOOl) [229]. The desorption and dissociation barriers of bridge-site NO were previously measured to be 30 and 19.2 kcal/mole, respectively [202,203].…”

Section: Reactivity Of Nitric Oxide On Metal Surfacessupporting

confidence: 75%

“…For instance, the inorganic compound (CsHs)JCo3(NOh has a strong v(N-O) mode at 1405 em-lO[244,245], and the Rh analog of the above cobalt cluster has been reported to have a N-O stretch at 1392 cm-I[246]. Both studies assign these modes to NO bonded to three metal atoms in a hollow site.On the Ru(OOl) surface, a v(N-O) mode at 1379 to 1525 cm-I was observed and was attributed to threefold-site NO[227,228,229]. The LEED observation of NO adsorbed onto fcc hollow sites in the e( 4x2)-CCH3+NO unit cell is a direct calibration of N-O stretch at 1435 cm-l , based on HREELS measurements.…”

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confidence: 78%

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The structure, ordering, and chemistry of molecular overlayers on Rh(111) and Rh(100) single crystal surfaces: A vibrational spectroscopic and LEED crystallographic study

Kao¹

1988

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Section: Reactivity Of Nitric Oxide On Metal Surfacessupporting

confidence: 75%

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confidence: 78%

The structure, ordering, and chemistry of molecular overlayers on Rh(111) and Rh(100) single crystal surfaces: A vibrational spectroscopic and LEED crystallographic study

Kao¹

1988

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“…The Ru(0001) sample was cleaned by Ar 1 sputtering, followed by several annealing and oxidation cycles [8]. Coadsorption of N and O was achieved by adsorbing NO at 375 K. At this temperature NO completely dissociates into O and N adatoms [5,6,9,10]. Since the desorption of nitrogen and oxygen starts only at temperatures above 500 K, equal amounts of O and N are covering the surface.…”

Section: Regular Mixing In a Two-dimensional Lattice System: The Coadmentioning

confidence: 99%

Regular Mixing in a Two-Dimensional Lattice System: The Coadsorption of N and O on Ru(0001)

et al. 1998

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The coadsorption of N and O on Ru(0001) has been studied by scanning tunneling microscopy; by this technique we can distinquish between the two atomic adsorbates. N and O form a dense intermixed 2 3 2 phase in equilibrium with a dilute lattice gas. The two-dimensional "vapor pressure" of N, i.e., its concentration in the lattice gas, has been determined for various ratios of N and O in the dense phase by adjusting the total coverage of N and O. The resulting vapor pressure curve indicates a positive enthalpy of mixing, due to relatively weak N-O interactions in the dense phase. [S0031-9007(98)07374-8] PACS numbers: 82.65.Dp, 68.35.Bs Lattice models are well established for the theoretical description of multicomponent systems like liquid mixtures, alloys, solid solutions, etc. [1,2]. Because of their discrete nature, which allows the explicit calculation of thermodynamic properties within statistical concepts, lattice models very often provide an appropriate and feasible mathematical description of these systems [3]. Nowadays, powerful computers allow the simulation of such models even for complicated systems [4]. Direct experimental verification of thermodynamic properties of such a system has, however, so far been lacking and will be presented in this paper.By applying scanning tunneling microscopy (STM) to the two-dimensional (2D) lattice system of coadsorbed O and N atoms on a Ru(0001) surface, we were able to directly determine the atomic configurations of this binary mixture. N and O atoms are shown to form two phases coexisting on the surface, a dense intermixed 2 3 2 phase in equilibrium with a dilute lattice gas phase. The thermodynamic quantities like the composition of the dense phase as well as the concentrations of the components in the lattice gas phase, i.e., their 2D partial pressures, were derived by simply counting the individual atoms.N and O were coadsorbed on the Ru(0001) surface by dissociative adsorption of NO [5,6] where all adatoms occupy equivalent hcp sites of the substrate lattice. The NO dissociation results in equal total amounts of N and O, while the atomic compositions of the different phases and hence also the partial pressures in the lattice gas phase vary with the overall coverage. By varying the exposure to NO, it became possible to derive the 2D N partial pressure for various ratios of N and O in the dense phase. The thus derived data indicate a positive enthalpy of mixing, reflecting the interactions of the adsorbates in the dense phase. These experimental results are compared with predictions from a simple lattice model for a binary mixture in 2D, from which a weak attractive third nearest neighbor ͑3nn͒ interaction between the O and N atoms is derived.The STM experiments were performed in a UHV chamber with a base pressure below 1 3 10 210 mbar, described in detail in [7]. The Ru(0001) sample was cleaned by Ar 1 sputtering, followed by several annealing and oxidation cycles [8]. Coadsorption of N and O was achieved by adsorbing NO at 375 K. At this temperature NO complet...

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“…[12] Upon adsorption, the NO molecules can diffuse across the surface until they dissociate, mainly at defects (for example, at atomic steps), [13] which indicates that the dissociation is an activated process. The resulting N atoms are easily resolved by the STM as almost stationary dark dots, whereas O atoms are more difficult to see at low coverages because of their greater mobility.…”

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confidence: 99%

Atomic‐Scale Evidence for an Enhanced Catalytic Reactivity of Stretched Surfaces

et al. 2003

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High resolution electron energy loss investigations of the adsorption of NO on the clean and oxygen precovered Ru(001) surface

Cited by 69 publications

References 31 publications

The structure, ordering, and chemistry of molecular overlayers on Rh(111) and Rh(100) single crystal surfaces: A vibrational spectroscopic and LEED crystallographic study

The structure, ordering, and chemistry of molecular overlayers on Rh(111) and Rh(100) single crystal surfaces: A vibrational spectroscopic and LEED crystallographic study

Regular Mixing in a Two-Dimensional Lattice System: The Coadsorption of N and O on Ru(0001)

Atomic‐Scale Evidence for an Enhanced Catalytic Reactivity of Stretched Surfaces

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