Interaction of oxygen with silver at high temperature and atmospheric pressure: A spectroscopic and structural analysis of a strongly bound surface species

Bao, Xinhe; Mühler, Martin; Schedel‐Niedrig, Th.; Schlögl, Robert

doi:10.1103/physrevb.54.2249

Cited by 253 publications

(257 citation statements)

References 34 publications

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“…This species represents strongly bound atomic oxygen embedded in the outer layers of silver, with oxygen atoms occupying part of the silver positions in the silver crystal lattice. The peak at 530.5 eV can be assigned to subsurface oxygen embedded in octahedral holes or O β in our old classification [45]. The location of these oxygen species in the subsurface region is in line with its inactivity towards ethylene.…”

Section: Resultsmentioning

confidence: 77%

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Combined in situ XPS and PTRMS study of ethylene epoxidation over silver

Bukhtiyarov

Nizovskiĭ

Bluhm

et al. 2006

Journal of Catalysis

130

129

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Ethylene epoxidation over silver was investigated by combined in-situ X-ray photoelectron spectroscopy (XPS) and proton-transfer reaction mass-spectrometry (PTRMS) at temperatures from 300 to 520 K and in the pressure range from 0.07 to 1 mbar. Ethylene oxide was present among the reaction products at T ≥ 420 K and P ≥ 0.3 mbar. The catalytically active surface contains two oxygen species -nucleophilic and electrophilic oxygen. The observed correlation between the abundance of electrophilic oxygen and the yield of ethylene oxide expressed as C 2 H 4 O partial pressure indicates that namely this oxygen species oxidizes ethylene to ethylene oxide. Opposite trend is observed for nucleophilic oxygen: the higher is the abundance of this species, the lower is the yield of ethylene oxide. This result is in line with the known fact that nucleophilic oxygen due to its oxidic nature is active in total oxidation of ethylene to CO 2 and H 2 O. The low activity of silver at T < 420 K is caused by the presence of carbonates and carbonaceous residues at the silver surface that reduce the available silver surface area for the catalytic reaction. Reduction of the surface area available for the formation of active species due to accumulation of the embedded oxygen species explains also the decrease of the rate of ethylene oxide formation with time observed for T ≥ 470 K.

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Section: Resultsmentioning

confidence: 77%

“…The binding energy of the feature at ~ 529.0 eV is close to that of the so-called O γ oxygen, which has been extensively studied by Schlögl et al [45,46]. This species represents strongly bound atomic oxygen embedded in the outer layers of silver, with oxygen atoms occupying part of the silver positions in the silver crystal lattice.…”

Section: Resultsmentioning

confidence: 89%

Combined in situ XPS and PTRMS study of ethylene epoxidation over silver

Bukhtiyarov

Nizovskiĭ

Bluhm

et al. 2006

Journal of Catalysis

130

129

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“…In ammonia synthesis over Fe catalysts, the formation of substoichiometric Fe nitrides is discussed [9]. For the partial oxidation of methanol to formaldehyd over copper catalysts the formation of copper suboxides was observed at ambient gas pressures of 10 mbar [130] and on silver catalysts a reactive O γ species embedded into the outermost Ag layer was found [131]. In both cases, these O species differ from adsorbed O or regular oxide species with respect to their electronic structure and reactivity.…”

Section: Microkinetic Modeling Of Surface Reactionsmentioning

confidence: 99%

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Weiß

Ranke

2002

Progress in Surface Science

579

610

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Metal-oxide based catalysts are used for many important synthesis reactions in the chemical industry. A better understanding of the catalyst operation can be achieved by studying elemantary reaction steps on well-defined model catalyst systems. For the dehydrogenation of ethylbenzene to styrene in the presence of steam both unpromoted and potassium promoted iron-oxide catalysts are active. Here we review the work done over unpromoted single-crystalline FeO(111), Fe 3 O 4 (111) and α-Fe 2 O 3 (0001) films grown epitaxially on Pt(111) substrates. Their geometric and electronic surface structures were characterized by STM, LEED, electron microscopy and electron spectroscopic techniques. In an integrative approach, the interaction of water, ethylbenzene and styrene with these films was investigated mainly by thermal desorption and photoelectron emission spectroscopy. The adsorptiondesorption energetics and kinetics depend on the oxide surface terminations and are correlated to the electronic structures and acid-base properties of the corresponding oxide phases, which reveal insight into the nature of the active sites and into the catalytic function of semiconducting oxides in general. Catalytic studies, using a batch reactor arrangement at high gas pressures and post reaction surface analysis, showed that only α-Fe 2 O 3 (0001) containing surface defects is catalytically active, whereas Fe 3 O 4 (111) is always inactive. This can be related to the elementary adsorption and desorption properties observed in ultrahigh vacuum, which indicates that the surface chemical properties of the iron-oxide films do not change significantly across the "pressure-gap". A model is proposed according to which the active site involves a regular acidic surface sites and a defect site next to it. The results on metal-oxide surface chemistry also have implications for other fields, such as environmental science, biophysics and chemical sensors.-2 -"2kyEi9FYSQjBVrZxIPQ.FHIAC_WRa02_review.doc", Datum: 19.02.03

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“…Such an idea [73] put forward for other mixed metal species contradicts the site isolation concept as it would not allow to control the timing of substrate oxidation and oxygen reduction and thus violate the concept of minimization of reactive species for maximising selectivity. The exchange of electrophilic oxygen for redox equivalents is a facile process [56,[74][75][76] when the site can easily change its oxidation state without having to break bonds to many neighbouring atoms. Handing over an oxygen atom to the adsorbate requires a change in local coordination such as from a corner sharing to an edge sharing form.…”

Section: Size and Functions Of Active Sitesmentioning

confidence: 99%

Active Sites for Propane Oxidation: Some Generic Considerations

Schlögl

2011

Top Catal

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Based on experimental observations about structure and dynamics of the reactive surface of the M1 phase some considerations are made about the nature and size of active sites. In analyzing the stoichiometry of the reactions following activation of propane it occurs that for dehydrogenation small sites are desirable being just sufficient to re-activate oxygen without kinetic hindrance. For deeper oxidation to acrylic acid (AA) the sites should be larger to accommodate all redox equivalents and oxygen species required for one transformation. A qualitative model for size and composition of the active site is made. It is likely that the active site consists on a VxOy species of strictly 2-D nature. This follows the structural suggestion for the active site on the a-b-plane of the M1 structure. The role of Te in moderating the active site is discussed. The suggestions are discussed in comparing requirements for oxidative dehydrogenation of propane (ODP) with those for AA synthesis.

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Interaction of oxygen with silver at high temperature and atmospheric pressure: A spectroscopic and structural analysis of a strongly bound surface species

Cited by 253 publications

References 34 publications

Combined in situ XPS and PTRMS study of ethylene epoxidation over silver

Combined in situ XPS and PTRMS study of ethylene epoxidation over silver

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

Active Sites for Propane Oxidation: Some Generic Considerations

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