STM characterization of size-selected V1, V2, VO, and VO2 clusters on a TiO2(110)-(1×1) surface at room temperature

Price, Scott P.; Tong, Xiao; Ridge, Claron J.; Shapovalov, Vladimir; Hu, Zhenpeng; Kemper, Paul R.; Metiu, Horia; Bowers, Michael T.; Buratto, Steven K.

doi:10.1016/j.susc.2011.02.016

Cited by 26 publications

(35 citation statements)

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“…However, in experiments performed using size selected silver clusters, it was observed that silver clusters containing 50 to 250 atoms deposited onto HOPG diffuse and coalesce into larger nanoparticles with a diameter of about 14 nm, irrespective of the incident gas phase cluster size [13]. In contrast, our knowledge of the size-dependent surface behavior of metal compound clusters (e.g, metal oxides [20][21][22], sulfides [23], nitrides), is extremely limited despite their importance in catalysis and material science [24].…”

Section: Introductionmentioning

confidence: 97%

Size Selected Clusters on Surfaces

Tang

Wang

et al. 2013

J. Phys.: Conf. Ser.

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Section: Introductionmentioning

confidence: 97%

Size Selected Clusters on Surfaces

Tang

Wang

et al. 2013

J. Phys.: Conf. Ser.

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“…On a rutile TiO 2 support, the atomic structures of V 1 , V 2 , VO, and VO 2 clusters have been investigated using STM and DFT. 11 More recently, combining XPS (X-ray photoelectron spectroscopy), AR-PD (angle resolved photoelectron diffraction), and DFT calculations, VO x nanoclusters supported on rutile TiO 2 were found to have a strong tendency toward aggregating into polynuclear nanoclusters. 12 The structure of these VO x nanoclusters was proposed to be V 4 O 6 aligned along the [001] direction of the TiO 2 substrate.…”

Section: ■ Introductionmentioning

confidence: 99%

Computational Study of Structure and Reactivity of Oligomeric Vanadia Clusters Supported on Anatase and Rutile TiO₂ Surfaces

Duan

Henkelman

2015

J. Phys. Chem. C

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We use density functional theory to examine structure− activity relationships of small vanadia clusters supported on anatase TiO 2 (001) and rutile TiO 2 (110) surfaces. A thermodynamic analysis indicates that the vanadia monomer cluster can be stabilized on the anatase TiO 2 (001) surface in a catalytically relevant oxygen environment. On the other hand, vanadia clusters tend to aggregate into dimers on the rutile TiO 2 (110) surface because this surface binds the monomer less strongly as compared to anatase. Hydrogen adsorption is found to be exothermic on the vanadia monomer adsorbed on both supports, enhanced by a charge transfer between the adsorbate and the substrate. There is no such charge transfer on vanadia dimers and tetramers, where the hydrogen adsorption energies are similar to that on the single crystal V 2 O 5 (001) surface. The improved catalytic performance of the anatase support can be attributed to the ability of this surface to stabilize the catalytically active vanadia monomer clusters. ■ INTRODUCTIONThe growing demand of olefins and aldehydes as raw materials in industry calls for catalysts that can produce them in an efficient and economical way. One promising way is the catalytic oxidative dehydrogenation (ODH) of light alkanes and alcohols to the corresponding alkenes and aldehydes. The advantages of ODH over conventional nonoxidative routes rely on the fact that the ODH reaction is (i) exothermic and can operate at low temperature and (ii) minimizes coke deposition which eventually deactivates the catalysts. Oxide-supported vanadium oxide catalysts (VO x ) have been demonstrated to exhibit high activity for the ODH reaction. 1−3 However, the yield of desirable products is still limited by undesirable total combustion reactions. An increase in the activity and selectivity of this reaction would be aided by a fundamental understanding of the structure−activity relationship at the molecular level.The structure−activity relationship of VO x has long been pursued in experiments, 4−8 where different structures of VO x are prepared by varying the vanadium loading on a given support. With increasing vanadium loading, VO x catalysts are proposed to change in structure from monomers, oligomers, monolayers, to 3D crystalline V 2 O 5 nanoparticles. The structure of VO x clusters at different coverages and their corresponding performance are characterized and measured to establish structure−activity relationships. For the TiO 2 support, which is of interest in this study, it is believed that the turnover frequency (TOF) at the VO x /TiO 2 catalyst is relatively insensitive to coverage, whereas V 2 O 5 nanoclusters with a size of 1−2 nm exhibit high ODH activity. At higher coverages, the activity drops when extensive crystalline V 2 O 5 forms.Although these studies provide valuable insight, a structure− activity relationship with molecular resolution should be pursued since the currently employed characterization methods do not provide unambiguous structural information at the atomic scale. Density f...

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“…There are at least 15 different vanadium oxides reported till now, such as VO, V 2 O 3 , VO 2 , V 2 O 5, V 6 O 13 and so on. Vanadium oxide thin films have been widely studied for optical, electrical, electrochemical, thermo-chromic and thermal switching materials [1][2][3][4][5][6][7][8][9][10][11]. The interest in these materials has increased in the last few years due to their potential scientific and technological applications, for example as a catalyst [12], a window for solar cells [13], electrochromic devices [14], electronic information displays [15] and color memory devices [16,17].…”

Section: Introductionmentioning

confidence: 99%

Structural And Optical Properties Of VOx Thin Films

Schneider

2015

Archives of Metallurgy and Materials

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VO x thin films were deposited on Corning glass, fused silica and Ti foils by means of rf reactive sputtering from a metallic vanadium target. Argon-oxygen gas mixtures of different compositions controlled by the flow rates were used for sputtering. Influence of the oxygen partial pressure in the sputtering chamber on the structural and optical properties of thin films has been investigated.Structural properties of as-sputtered thin films were studied by X-ray diffraction at glancing incidence, GIXD. Optical transmittance and reflectance spectra were recordedwith a Lambda 19 Perkin-Elmer double spectrophotometer. Thickness of the films was determined from the profilometry. It has been confirmed by XRD that the deposited films are composed mainly of V 2 O 5 phase. The estimated optical band gap of 2.5 eV corresponds to V 2 O 5 .Keywords: VO x thin films, reactive sputtering, microstructure, optical properties, energy band gap Cienkie warstwy VO x były nanoszone na szkło Corning metodą rozpylania magnetronowego rf. Jako katody użyto metalicznego wanadu. Były one nanoszone w komorze wypełnionej mieszaniną argonu i tlenu w różnych proporcjach przy ustalonych przepływach. Zbadano wpływ ciśnienia parcjalnego tlenu w komorze na własności strukturalne i optyczne otrzymanych warstw.Własności strukturalne cienkich warstw zostały określone metodą rozpraszania promieniowania rentgenowskiego padają-cego pod małymi kątami (GIXD). Widma optyczne transmitancji i odbicia zostały wykonane przy użyciu spektrometru Lambda 19 Perkin-Elmer. Grubość badanych warstw zmierzono za pomocą profilometru.Pomiary XRD potwierdziły, że otrzymane warstwy składają się głównie z fazy V 2 O 5 . Wyznaczona optycznie przerwa energetyczna wynosząca 2.5 eV odpowiada przerwie energetycznej V 2 O 5 .

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STM characterization of size-selected V1, V2, VO, and VO2 clusters on a TiO2(110)-(1×1) surface at room temperature

Cited by 26 publications

References 26 publications

Size Selected Clusters on Surfaces

Size Selected Clusters on Surfaces

Computational Study of Structure and Reactivity of Oligomeric Vanadia Clusters Supported on Anatase and Rutile TiO₂ Surfaces

Structural And Optical Properties Of VOx Thin Films

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STM characterization of size-selected V1, V2, VO, and VO2 clusters on a TiO2(110)-(1×1) surface at room temperature

Cited by 26 publications

References 26 publications

Size Selected Clusters on Surfaces

Size Selected Clusters on Surfaces

Computational Study of Structure and Reactivity of Oligomeric Vanadia Clusters Supported on Anatase and Rutile TiO2 Surfaces

Structural And Optical Properties Of VOx Thin Films

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Product

Resources

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Computational Study of Structure and Reactivity of Oligomeric Vanadia Clusters Supported on Anatase and Rutile TiO₂ Surfaces