Au Dimers on Thin MgO(001) Films: Flat and Charged or Upright and Neutral?

Simic-Milosevic, Violeta; Heyde, Markus; Nilius, Niklas; König, Thomas; Rust, Hans-Peter; Sterrer, Martin; Risse, Thomas; Freund, Hans‐Joachim; Giordano, Livia; Pacchioni, Gianfranco

doi:10.1021/ja8024388

Cited by 62 publications

(60 citation statements)

References 24 publications

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“…4.13 on thin MgO films is therefore an experimental verification that the concept of charge-transfer prevails also for small aggregates on thin oxide films. 388,389 This conclusion was corroborated with two DFT studies, calculating the stability of differently-shaped Au aggregates on MgO/Ag(001) 388 and MgO/Mo(001) films. 368 On the MgO/Ag surface, the Au dimer as the smallest cluster occurs in two stable configurations, namely as an upright Au 2 bound to an O 2-surface atom, and as a flat-lying species attached to two Mg 2+ or two hollow sites in the oxide film.…”

Section: Linear Ad-chainssupporting

confidence: 58%

“…The formation of anionic gold species on thin oxide films affects also their aggregation into larger particles at higher metal exposure, as demonstrated by the following STM experiments on MgO 388,389 and alumina thin films. 375 Experimentally, the aggregation of charged adspecies can be promoted by metal deposition at elevated temperature (>50 K), where an enhanced atom mobility helps overcoming the inter-atomic Coulomb repulsion.…”

Section: Linear Ad-chainsmentioning

confidence: 86%

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Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

Nilius

2009

Surface Science Reports

221

233

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The preparation of thin oxide films on metal supports is a versatile approach to explore the properties of oxide materials that are otherwise inaccessible to most surface science techniques due to their insulating nature. Although substantial progress has been made in the characterization of oxide surfaces with spatially averaging techniques, a local view is often essential to provide comprehensive understanding of such systems. The scanning tunneling microscope (STM) is a powerful tool to obtain atomic-scale information on the growth behavior of oxide films, the resulting surface morphology and defect structure.

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Section: Linear Ad-chainssupporting

confidence: 58%

Section: Linear Ad-chainsmentioning

confidence: 86%

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

Nilius

2009

Surface Science Reports

221

233

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“…Charging of an adsorbate is considered crucial for controlling such adsorption properties as structure and energy. Recent experimental and theoretical studies reveal that the Au adsorbate, [29][30][31][32] whether a single atom or clusters, and molecular adsorbates, such as O 2 ͑Ref. 33͒ and NO 2 , [34][35][36] can be charged on a thin oxide film surface.…”

mentioning

confidence: 99%

Controlling water dissociation on an ultrathin MgO film by tuning film thickness

et al. 2010

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Periodic density-functional theory calculations at the single-molecule level were used to study dissociation of water on ultrathin MgO films with varying thickness deposited on the Ag͑100͒ surface. The enhanced chemical activity for water dissociation on MgO/Ag͑100͒ originates from the greater stability of dissociated products, which is due in turn to the strong hybridization of their electronic states at the oxide-metal interface. Our results provide insights into the superiority of the monolayer MgO film surface over the bulk surface and the use of the film thickness to control heterogeneous catalysis in water dissociation. DOI: 10.1103/PhysRevB.82.085413 PACS number͑s͒: 68.43.Bc, 68.47.Gh, 82.65.ϩr The interaction of water with oxide surfaces has long been of fundamental importance to various fields of science, including geochemistry, electrochemistry, and catalysis. 1,2Understanding how water molecules dissociate on oxide surfaces is crucial not only for revealing various solid-liquid interface phenomena but also for controlling chemical reactions involving water dissociation. Water dissociation on the MgO͑100͒ bulk surface has so far been observed to occur only if the dissociation products are stabilized by defects or neighboring water molecules. [3][4][5][6] Compared with the MgO bulk surface, the chemical activity of water dissociation is remarkably enhanced on a single monolayer ͑ML͒ MgO film deposited on a Ag͑100͒ surface. [7][8][9][10] In studies using highresolution electron energy loss spectroscopy combined with x-ray photoemission spectroscopy, Savio et al. reported that the dissociation probability of water at room temperature on the 1-ML MgO film surface increases by a factor of 6 compared with a multilayer film. 7,8 They suggest that this remarkable enhancement in chemical reactivity originates in the border sites of the 1-ML oxide film in contact with a metal substrate. However, a theoretical study by Ferrari et al. does not support the role of the metal substrate at the border of the 1-ML oxide film as an explanation for the high chemical activity of the 1-ML MgO film compared with bulk MgO.11 In photoemission and Auger electron spectroscopy experiments, Altieri et al. found that both border and terrace sites enhance water dissociation compared with corresponding sites of bulk MgO.9,10 They suggest that the metal substrate beneath the terrace sites of MgO film plays a pivotal role in water dissociation. The discrepancy between these experimental results might be due to the difficulty in precisely controlling the number of defects, the size, and the thickness of the MgO thin film at a monolayer limit. 12,13 Although experimental studies so far have definitely demonstrated the superiority of ultrathin MgO film over bulk MgO for water dissociation, such details as the phenomenon's dependence on film thickness and the contribution of defect-free terrace sites as venues for chemical activity have not been clarified and demand systematic study. [7][8][9][10] In particular, Shin et al. have demons...

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“…The large modifications in adsorption owing to the metal support are not limited to Au or other transition metal single atoms, but significant changes are also seen in Au cluster geometries, charge states, and adsorption energies on metal-supported MgO films [107][108][109][110][111] . For comparison, on bulk MgO the smallest Au N (N=2-6) clusters favour minimal wetting with 14 one or two Au atoms in contact with oxide ions 28,94,108,112,113 .…”

Section: Preparation and Properties Of Modified Simple Oxidesmentioning

confidence: 99%

Tailoring oxide properties: An impact on adsorption characteristics of molecules and metals

Honkala

2014

Surface Science Reports

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Au Dimers on Thin MgO(001) Films: Flat and Charged or Upright and Neutral?

Cited by 62 publications

References 24 publications

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

Controlling water dissociation on an ultrathin MgO film by tuning film thickness

Tailoring oxide properties: An impact on adsorption characteristics of molecules and metals

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