Thermodynamic and spectroscopic properties of oxygen on silver under an oxygen atmosphere

Jones, Travis E.; Rocha, Túlio C. R.; Knop‐Gericke, Axel; Stampfl, Catherine; Schlögl, Robert; Piccinin, Simone

doi:10.1039/c5cp00342c

Cited by 130 publications

(175 citation statements)

References 131 publications

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“…The relative values computed in this way were shifted to absolute values using a reference state calculation on a (2x2x2) cell of Ag 2 CO 3 and the corresponding measured binding energies [39]. We have previously found this approach to give computed binding energies to within ±0.3 eV of experimental values [15]. For a full description of our approach see Reference [15].…”

Section: Theoretical and Experimental Methodsmentioning

confidence: 99%

“…Instead, at the oxygen chemical potentials required for epoxidation surface reconstructions with Ag δ+ sites available for ethylene adsorption are formed [6,10,11]. Such structures have been observed directly by scanning tunneling microscopy (STM) [10,11] and the presence of chemically similar oxygen species under near ambient pressure conditions can also be inferred by in situ X-ray photoelectron and near edge X-ray absorption spectroscopies (XPS and NEXAFS) [12][13][14][15]. (Note that in the earlier publications the p(4x4) phase on Ag(111), which has played a central role in the discussion, was considered a 2D…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, there is scarce evidence that a measurable amount of the more ionic type of oxygen modeled by DFT is present under epoxidation conditions [15,36] because it forms surface reconstructions at oxygen chemical potentials relevant for ethylene epoxidation [10,19,21].…”

Section: Introductionmentioning

confidence: 99%

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Oxidation of Ethylene on Oxygen Reconstructed Silver Surfaces

et al. 2016

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We report on theoretical and experimental studies of the reactivity of ethylene with oxygen in two well-known oxygen induced surface reconstructions on silver, the p(2x1) reconstruction on the Ag(110) and the p(4x4) reconstruction on the Ag(111) surfaces. Density functional theory calculations demonstrate that ethylene can react with oxygen on both surfaces to form an oxametallacycle that can decompose into either ethylene oxide or a CO 2 precursor, acetaldehyde.The activation energy associated with acetaldehyde formation is predicted to be 0.4 eV lower than that associated with epoxide formation on both surfaces, though we find lower barriers for all elementary steps on the p(4x4) reconstruction due to its unique structural dynamics. Our calculations predict these dynamics make the p(4x4) reconstruction active in acetaldehyde formation at room temperature. Experiments performed by exposing the p(4x4) reconstruction to ethylene at room temperature support this finding with CO 2 the only carbonaceous product formed during temperature programed desorption. Our results unambiguously demonstrate that, alone, these oxygen reconstructions are not selective in ethylene epoxidation on silver.

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Section: Theoretical and Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Oxidation of Ethylene on Oxygen Reconstructed Silver Surfaces

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“…Of the oxygen induced Ag surface reconstructions, the p(4×4) reconstruction of the (111) surface has been the most widely studied and is believed to be the most stable structure under conditions relevant for EO catalysis (10,35 (36)(37). Over the next thirty years, a variety of models for a p(4×4)-O/Ag structure were proposed and subsequently improved upon (38).…”

Section: Introductionmentioning

confidence: 99%

“…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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Atomic‐Scale Observation of Irradiation‐Induced Surface Oxidation by In Situ Transmission Electron Microscopy

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Jones

Fan

et al. 2016

Adv Materials Inter

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Irradiation of materials with high energy particles can induce structural transitions or trigger chemical reactions. Understanding the underlying mechanism for irradiation-induced phenomena is of both scientific and technical importance. Here, CdS nanoribbons are used as a model system to study structural and chemical evolution under electron-beam irradiation by in situ transmission electron microscopy. Real-time imaging clearly shows that upon irradiation, CdS is transformed to CdO with the formation of orientation-dependent relationships at surface. The structural transition can always be triggered with a dose rate beyond 601 e/Å²s in this system. A lower dose rate instead leads to the deposition of an amorphous carbon layer on the surface. Based on real-time observations and density functional theory calculations, a mechanism for the oxidation of CdS to CdO is proposed. It is essentially a thermodynamically driven process that is mediated by the formation of sulfur vacancies due to the electron-beam irradiation. It is also demonstrated that the surface oxidation can be suppressed by pre-depositing a conductive carbon layer on the CdS surface. The carbon coating can effectively reduce the rate of sulfur vacancy creation, thus decreasing defect-mediated oxidation. In addition, it isolates the active oxygen radicals from the ribbon, blocking the pathway for oxygen diffusion

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Thermodynamic and spectroscopic properties of oxygen on silver under an oxygen atmosphere

Cited by 130 publications

References 131 publications

Oxidation of Ethylene on Oxygen Reconstructed Silver Surfaces

Oxidation of Ethylene on Oxygen Reconstructed Silver Surfaces

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

Atomic‐Scale Observation of Irradiation‐Induced Surface Oxidation by In Situ Transmission Electron Microscopy

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