Model catalyst studies of the strong metal–support interaction: Surface structure identified by STM on Pd nanoparticles on TiO2(110)

Bowker, Michael; Stone, Peter; Morrall, P.; Smith, R. D.; Bennett, R. A.; Perkins, Neil D.; Kvon, Ren I.; Pang, Chi L.; Fourré, Elodie; Hall, Matthew S.

doi:10.1016/j.jcat.2005.05.024

Cited by 107 publications

(137 citation statements)

References 28 publications

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“…X-ray photoelectron spectroscopy showed Ti 3þ present in the SMSI state. This is in contrast to Bennett et al 21,26 who showed the layer on Pd to be Ti 2þ -like by using take-off angle variations in XPS, though the effect on CO adsorption 27 was similar to that observed by Linsmeier and Taglauer. 25 Reactivity measurements by Bonanni 28 suggest that high-temperature annealing of Pt on reduced TiO 2 results in the encapsulation of Pt by a reduced titania layer, agreeing with a mechanism proposed by Fu et al…”

Section: Introductioncontrasting

confidence: 61%

Section: Pd/tio 2 (110)mentioning

confidence: 98%

“…21,26 After annealing to high temperature such films can be flat 26 and show reasonably good LEED patterns. 21,26 However, annealing to very high-temperature results Figure 5 Pd 3d/Ti 2p X-ray photoelectron spectroscopy (XPS) area ratios for each surface during deposition. symbols are for deposition onto the sputtered surface, green for the sputter-annealed surface, and blue for the surface sputtered and annealed in oxygen and (inset) normalized to the Pd/Ti ratio for the sputtered surface at 300 s Figure 6 The change in Pd3d/Ti 2p area ratio with annealing temperature for the three prepared surfaces Figure 7 a The variation in the Ti 2p X-ray photoelectron spectroscopy (XPS) signal with increasing temperature for the sputtered surface with Pd post-dosed.…”

Section: Pd/tio 2 (110)mentioning

confidence: 98%

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Pd deposition on TiO₂(110) and nanoparticle encapsulation

Bowker

Sharpe

2015

Catalysis, Structure & Reactivity

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The effect of sputtering, annealing and oxidation on the surface properties of TiO 2 (110), and on the same surfaces with nanoparticles present, has been investigated. Sputtering the crystal clean gives a much reduced surface with Ti 2þ as the dominant species. This surface is mainly Ti 3þ,4 þ after annealing in vacuum.Oxidation reduces the surface Ti 3þ considerably. WhenPd nanoparticles are annealed on any of the investigated titania surfaces, the particles become encapsulated by a film of titanium oxide. This is particularly noticeable in ion scattering spectroscopy (ISS) where the Pd:Ti ratio drops by a factor of 300 after annealing to 750 K, indicating complete coverage of the Pd nanoparticles by the oxide film. This happens most easily for the nanoparticles deposited on the reduced surfaces (beginning at ,673K) but also occurs for the very oxidized surface at , 773 K. Thus, reduced Ti from the subsurface region can migrate onto the Pd surface to form the sub-oxide, the sub-oxide being a thin TiO-like layer.

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Section: Introductioncontrasting

confidence: 61%

Section: Pd/tio 2 (110)mentioning

confidence: 98%

Section: Pd/tio 2 (110)mentioning

confidence: 98%

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Pd deposition on TiO₂(110) and nanoparticle encapsulation

Bowker

Sharpe

2015

Catalysis, Structure & Reactivity

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“…On the other hand, metals supported on the reducible oxides often exhibit so-called strong metal-support interaction (SMSI) [1][2][3][4][5][6], which in many cases manifests itself by encapsulation (decoration) of the metal particles by a thin layer stemming from the oxide support. Formation of thin titania layers on Pt and Pd particles upon heating in vacuo has recently been investigated by high resolution scanning tunnelling microscopy (STM) [7][8][9]. It is rather obvious that the decoration will suppress catalytic reactions occurring on metal surfaces and be particularly detrimental for structure sensitive reactions.…”

Section: Introductionmentioning

confidence: 99%

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Sun

Qin

Lewandowski

et al. 2009

Journal of Catalysis

220

236

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Abstract. CO oxidation on a clean Pt(111) single crystal and thin iron oxide films grown on Pt(111) was studied at different CO:O 2 ratios (between 1:5 and 5:1) and partial pressures up to 60 mbar at 400 -450 K. Structural characterization of the model catalysts was performed by scanning tunneling microscopy, low energy electron diffraction, Auger electron spectroscopy and temperature programmed desorption. It is found that monolayer FeO (111) films grown on Pt(111) are much more active than clean Pt(111) and nm-thick Fe 3 O 4 (111) films at all reaction conditions studied. Post-characterization of the catalysts revealed that at CO:O 2 >1 the FeO(111) film dewets the Pt surface with time, ultimately resulting in highly dispersed iron oxide particles on Pt(111). The film dewetting was monitored in situ by polarisation-modulated infrared reflection absorption spectroscopy. The reaction rate at 450 K exhibited first order for O 2 and non-monotonously depended on CO pressure. In O 2 -rich ambient the films were enriched with oxygen while maintaining the long range ordering.Based on the structure-reactivity relationships observed for the FeO/Pt films, we propose that the reaction proceeds through the formation of a well-ordered, oxygen-rich FeO x (1 < x < 2) film that reacts with CO through the redox mechanism. The reaction induced dewetting in fact deactivates the catalyst. The results may aid in our deeper understanding of reactivity of metal particles encapsulated by thin oxide films as a result of strong metal support interaction.

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“…Thus, the investigation of the properties of supported metal clusters and the influence of the metal-oxide interfaces are of great interest. In particular, titanium oxides are often correlated with the so-called strong metal support interaction (SMSI) effect, which describes the influence of a transition metal oxide support on noble metal clusters yielding novel catalytic properties [1][2][3][4][5][6][7]. In order to understand this effect, well-defined model systems are needed.…”

Section: Introductionmentioning

confidence: 99%

Distribution of Pd clusters on ultrathin, epitaxial TiOx films on Pt3Ti(111)

Breinlich¹,

Buchholz²,

Moors³

et al. 2016

Nano Online

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Scanning tunnelling microscopy (STM) was used to investigate the nucleation and growth of palladium clusters on two different, ultrathin, epitaxial, titania films grown on a Pt 3 Ti(111) surface. The first oxide phase, z'-TiO x , is anisotropic and consists of parallel stripes separated by trenches. Defects (i.e., oxygen vacancies) in this structure are confined to these trenches and act as nucleation sites. Therefore, the Pd clusters are mostly arranged in unidirectional rows along the trenches, creating a template effect. The second phase, w'-TiO x , exhibits a hexagonal, long range, (7 × 7)R21.8°, Moiré-type superstructure with fewer and shallower defects, making the template effect less discernible. 2007

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Model catalyst studies of the strong metal–support interaction: Surface structure identified by STM on Pd nanoparticles on TiO2(110)

Cited by 107 publications

References 28 publications

Pd deposition on TiO₂(110) and nanoparticle encapsulation

Pd deposition on TiO₂(110) and nanoparticle encapsulation

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Distribution of Pd clusters on ultrathin, epitaxial TiOx films on Pt3Ti(111)

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Model catalyst studies of the strong metal–support interaction: Surface structure identified by STM on Pd nanoparticles on TiO2(110)

Cited by 107 publications

References 28 publications

Pd deposition on TiO2(110) and nanoparticle encapsulation

Pd deposition on TiO2(110) and nanoparticle encapsulation

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Distribution of Pd clusters on ultrathin, epitaxial TiOx films on Pt3Ti(111)

Contact Info

Product

Resources

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Pd deposition on TiO₂(110) and nanoparticle encapsulation

Pd deposition on TiO₂(110) and nanoparticle encapsulation