Revisiting the Structure of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>4</mml:mn><mml:mo>×</mml:mo><mml:mn>4</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math>Surface Oxide on Ag(111)

Schnadt, Joachim; Michaelides, Angelos; Knudsen, Jan; Vang, Ronnie T.; Lægsgaard, Erik; Scheffler, Matthias; Besenbacher, Flemming

doi:10.1103/physrevlett.96.146101

Cited by 149 publications

(131 citation statements)

References 22 publications

(21 reference statements)

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“…Recent works on O/Ag(111) [23,24,25] and O/Pd(111) [58] have shown that for these systems a multitude of structures with similar energetics can be found.…”

Section: Here Each Cu Is Linearly Bonded With Two O Atoms and Each O mentioning

confidence: 99%

“…3 to predict which structures will be present on the surfaces as a function of the copper content and the oxygen chemical potential. We also exploit the vast literature available for the O/Ag system [23,24] to include the most stable structures for the system in the absence of copper.…”

Section: Surface Phase Diagramsmentioning

confidence: 99%

“…In particular, given the conditions of operation of the Ag-Cu catalyst in realistic applications, the formation of surface oxides cannot be ruled out. It has been established that silver can form several surface oxide structures [23,24,25] and from the phase diagram of the Cu-O system, considering the temperature and oxygen pressure used in practical applications, but neglecting the effect of ethylene, the formation of CuO is expected, therefore suggesting that copper might also oxidate.…”

Section: Introductionmentioning

confidence: 99%

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Ag–Cu alloy surfaces in an oxidizing environment: A first-principles study

2009

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Recent experiments on model catalysts have shown that Ag-Cu alloys have improved selectivity with respect to pure silver for ethylene epoxidation. In this paper we review our first-principles investigations on the (111) surface of this alloy and present new findings on other low index surfaces.We find that, for every surface orientation, the presence of oxygen leads to copper segregation to the surface. Considering the alloy to be in equilibrium with an oxygen atmosphere and accounting for the effect of temperature and pressure, we compute the surface free energy and study the stability of several surface structures. Investigating the dependence of the surface free energy on the surface composition, we construct the phase diagram of the alloy for every surface orientation. Around the temperature, pressure and composition of interest for practical applications, we find that a limited number of structures can be present, including a thin layer of copper oxide on top of the silver surface and copper-free structures. Different surface orientations show a very similar behavior and in particular a single layer with CuO stoichiometry, significantly distorted when compared to a layer of bulk CuO, has a wide range of stability for all orientations. Our results are consistent with, and help explain, recent experimental measurements.

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“…Recent works on O/Ag(111) [23,24,25] and O/Pd(111) [58] have shown that for these systems a multitude of structures with similar energetics can be found.…”

Section: Here Each Cu Is Linearly Bonded With Two O Atoms and Each O mentioning

confidence: 99%

Section: Surface Phase Diagramsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ag–Cu alloy surfaces in an oxidizing environment: A first-principles study

2009

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“…Ag(111) surfaces exhibit a variety of different surface reconstructions induced by adsorbed oxygen (O ad ) (5,9), along with several other oxide species (10)(11)(12)(13)(14)(15)(16). The primary motivation to study the O/Ag(111) system is silver's importance as an industrial partial oxidation catalyst (11,17).…”

Section: Introductionmentioning

confidence: 99%

Thermally Selective Formation of Subsurface Oxygen in Ag(111) and Consequent Surface Structure

et al. 2016

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Derouin, Jonathan; Farber, Rachael G.; Turano, Marie E.; Iski, Erin V.; and Killelea, Daniel. Thermally Selective Formation of Subsurface Oxygen in Ag(111) Just Accepted "Just Accepted" manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides "Just Accepted" as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. "Just Accepted" manuscripts appear in full in PDF format accompanied by an HTML abstract. "Just Accepted" manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). "Just Accepted" is an optional service offered to authors. Therefore, the "Just Accepted" Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the "Just Accepted" Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these "Just Accepted" manuscripts. Thermally Selective Formation of Subsurface Oxygen inAg (111) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 AbstractA long-standing challenge in the study of heterogeneously catalyzed reactions on silver surfaces has been the determination of what oxygen species are of greatest chemical importance.This is due to the coexistence of several different surface phases on oxidized silver surfaces. A further complication is subsurface oxygen (O sub ). O sub are O atoms absorbed into the near surface of a metal, and are expected to alter the surface in terms of chemistry and structure, but these effects have yet to be well characterized. We studied oxidized Ag(111) surfaces after exposure to gas-phase O atoms to determine how O sub is formed and how its presence alters the resultant surface structure. Using a combination of surface science techniques to quantify O sub formation and the resultant surface structure, we observed that once 0.1 ML of O sub has formed, the surface dramatically, and uniformly, reconstructed to a striped phase at the expense of all other surface phases. Furthermore, O sub formation was hindered at temperatures above 500 K.The thermal dependence for O sub formation suggests that at industrial catalytic conditions of 475 -500 K for the epoxidation of ethylene-to-ethylene oxide, O sub would be present and is a factor in the subsequent reactivit...

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“…The adsorbed O atoms form an ordered surface structure with a (4 Â 4) lattice. It involves a reconstruction of the Ag(111) surface in which the structure of the topmost metal layer is modified, creating more favourable sites for the O atoms [26][27][28] . For the TPD experiments, the sample temperature was linearly ramped up (T ¼ T 0 þ bt, with initial temperature T 0 and heating rate b), and the desorbing O 2 was monitored with a quadrupole mass spectrometer (QMS).…”

Section: Combination Of Leem and Tpdmentioning

confidence: 99%

Desorption kinetics from a surface derived from direct imaging of the adsorbate layer

et al. 2014

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There are numerous indications that adsorbed particles on a surface do not desorb statistically, but that their spatial distribution is important. Evidence almost exclusively comes from temperature-programmed desorption, the standard method for measuring desorption rates. However, this method, as a kinetics experiment, cannot uniquely prove an atomic mechanism. Here we report a low-energy electron microscopy investigation in which a surface is microscopically imaged while simultaneously temperature-programmed desorption is recorded. The data show that during desorption of oxygen molecules from a silver single crystal surface, islands of oxygen atoms are present. By correlating the microscopy and the kinetics data, a model is derived that includes the shapes of the islands and assumes that the oxygen molecules desorb from the island edges. The model quantitatively reproduces the complex desorption kinetics, confirming that desorption is affected by islands and that the often used mean-field treatment is inappropriate.

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Revisiting the Structure of thep(4×4)Surface Oxide on Ag(111)

Cited by 149 publications

References 22 publications

Ag–Cu alloy surfaces in an oxidizing environment: A first-principles study

Ag–Cu alloy surfaces in an oxidizing environment: A first-principles study

Thermally Selective Formation of Subsurface Oxygen in Ag(111) and Consequent Surface Structure

Desorption kinetics from a surface derived from direct imaging of the adsorbate layer

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