Fundamental Reactions on Rutile TiO2(110) Model Photocatalysts Studied by High-Resolution Scanning Tunneling Microscopy

Wendt, Stefan; Vang, Ronnie T.; Besenbacher, Flemming

doi:10.1002/9780470823996.ch4

Cited by 3 publications

(5 citation statements)

References 134 publications

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“…The Ti atoms underneath the O br atoms are 6-fold coordinated as any other Ti atom in stoichiometric rutile. An Ar + sputtered and vacuum-annealed TiO 2 (110) crystal is an n-type semiconductor, and its surface has a number of O br vacancies. ,, In the STM images acquired on r -TiO 2 (110) surfaces [cf. Figure a] these O br vacancies (white rectangle) are imaged as faint protrusions on the dark O br rows. ,, Note that the empty-state STM images of the TiO 2 (110) surface are dominated by electronic effects, which leads to a reversed contrast, that is, bright rows correspond to the Ti troughs and geometrically protruding O br atoms appear dark. ,,, …”

Section: Resultsmentioning

confidence: 99%

“…An Ar + sputtered and vacuum-annealed TiO 2 (110) crystal is an n-type semiconductor, and its surface has a number of O br vacancies. 30,32,33 In the STM images acquired on r-TiO 2 (110) surfaces [cf. Figure 1a] these O br vacancies (white rectangle) are imaged as faint protrusions on the dark O br rows.…”

Section: Resultsmentioning

confidence: 99%

“…For studies performed under ultrahigh vacuum (UHV) conditions, the titania surface that has attracted the most attention is rutile TiO 2 (110)-(1 × 1). − The nucleation of Ag nanoclusters has also been investigated on this model support. In previous surface science studies, scanning tunneling microscopy (STM), − photoelectron spectroscopy (PES), and low-energy ion scattering (LEIS) have been used to characterize the Ag/TiO 2 (110) model catalytic surface.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Bonding of Silver Nanoparticles on Oxidized TiO₂(110)

et al. 2010

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The nucleation and growth of silver nanoclusters on TiO 2 (110) surfaces with on-top O adatoms (oxidized TiO 2 ), surface O vacancies and H adatoms (reduced TiO 2 ) have been studied. From the interplay of scanning tunneling microscopy/photoelectron spectroscopy experiments and density functional theory calculations, it is found that silver clusters are much more strongly bonded to oxidized TiO 2 (110) surfaces than to reduced TiO 2 (110) model supports. It is shown that electronic charge can be transferred from silver clusters to the oxidized TiO 2 (110) surface, as evidenced by the reappearance of the Ti3d defect state upon silver exposure. Furthermore, from both scanning tunneling microscopy data and density functional theory calculations the most favorable adsorption site of silver monomers on oxidized TiO 2 ( 110) is one that bridges between on-top O adatoms and regular surface O atoms nearby. † Part of the "D. Wayne Goodman Festschrift".

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhanced Bonding of Silver Nanoparticles on Oxidized TiO₂(110)

et al. 2010

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“…There were various microstructural (and structural) variables that influenced the photoelectrochemical results of the films, as summarized in Table . Decreasing grain sizes are beneficial in (i) providing large specific surface areas and the associated number of reaction sites (oxygen vacancies) for water photolysis and (ii) improving hole transport because the holes photogenerated in the outermost grains travel a shorter distance to the photoanode/electrolyte interface and oxidize water before they can recombine with the photogenerated electrons . Vacancy filling by oxidation may degrade the photoelectrochemical activity owing to the reduced number of reaction sites .…”

Section: Resultsmentioning

confidence: 99%

Tunable Photoelectrochemical Properties by Nanostructural Control in WO₃ Thin Films Prepared by Carboxylic Acid-Assisted Electrodeposition

et al. 2013

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The present work reports the synthesis of transparent (∼60–80% transmission) WO3 thin films by electrodeposition using peroxotungstic acid (PTA) solutions containing different carboxylic acids (formic, oxalic, and citric) of varying concentrations. The effects of these acids on the deposition kinetics and the morphological, mineralogical, optical, and photoelectrochemical properties of the films were investigated using scanning electron microscopy, X-ray diffraction, UV–vis spectrophotometry, and photoelectrochemical measurements. The deposited film thickness was dependent on the availability of hydronium ions (for hydrogen bonding with PTA ions) and molecular drag in the electrolytes, both of which were controlled through the use of carboxylic acids of different concentrations, degrees of dissociation, molecular weights, and associated sizes of the conjugate bases. The films consisted of agglomerates/particles (42–132 nm), the sizes of which decreased and the true porosities (<6%) of which increased with the amounts and sizes of the conjugate bases. These observations were considered to result from the separation of the PTA ions according to the amounts and sizes of the conjugate bases, the effects of which consequently changed the mechanisms of nucleation and grain growth. A nonlinear relationship between the grain sizes and the photoelectrochemical performances of the films was obtained where a maximum in the photocurrent density was observed for the film consisting of small agglomerates of ∼93 nm (deposited with 0.03 mol L–1 oxalic acid). This was considered to result from the positive balance of (i) surface reaction and recombination sites and (ii) the hole and electron transports in the film.

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“…There have been numerous studies of the structure and reactivity of many phases of TiO 2 ; in particular, rutile − and anatase , show good activity for water photo-oxidation. Rutile is the most well-studied polymorph, with numerous studies focusing on the lowest energy (110) surface. , The rutile (110) surface is favorably expressed in macroscopic crystal morphologies and has been understood to govern surface chemistry due to its minimal energy. − …”

Section: Introductionmentioning

confidence: 99%

Unraveling the Water Oxidation Mechanism on a Stoichiometric and Reduced Rutile TiO₂ (100) Surface Using First-Principles Calculations

Malik

Fredin

2023

J. Phys. Chem. C

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Photocatalytic water splitting provides a direct route to produce hydrogen and oxygen through the use of light and a water-splitting photocatalyst. While the photo-oxidation of water on rutile (110) surfaces has been extensively explored, only 64% of the surface of most rutile nanocrystals are (110). However, there have been only limited reports of the experimental and first-principles reactivity of the (100) and (101) surfaces, which make up the majority of the remaining surfaces. Herein, we report a systematic study of water oxidation on the rutile (100) surface under experimental conditions, including oxygen vacancies, surface adsorbates at pH = 0, and applied potential performed using density functional theory. Water oxidation mechanisms on oxygen-covered and reduced surfaces are characterized by their overpotential and rate-limiting steps. Maximal stability and activity were found for fully covered (100) surfaces and those with oxygen vacancies in the first two sublayers of the slab. The lowest overpotential for oxygen evolution was ∼0.86 V for a reduced rutile (100) surface with a vacancy in the second subsurface oxygen layer. The oxygen covered surface had an overpotential of ∼1.36 V. In both, the rate-limiting step was the transfer of a proton from a surface adsorbed OH to the electrolyte.

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Fundamental Reactions on Rutile TiO2(110) Model Photocatalysts Studied by High-Resolution Scanning Tunneling Microscopy

Cited by 3 publications

References 134 publications

Enhanced Bonding of Silver Nanoparticles on Oxidized TiO₂(110)

Enhanced Bonding of Silver Nanoparticles on Oxidized TiO₂(110)

Tunable Photoelectrochemical Properties by Nanostructural Control in WO₃ Thin Films Prepared by Carboxylic Acid-Assisted Electrodeposition

Unraveling the Water Oxidation Mechanism on a Stoichiometric and Reduced Rutile TiO₂ (100) Surface Using First-Principles Calculations

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Fundamental Reactions on Rutile TiO2(110) Model Photocatalysts Studied by High-Resolution Scanning Tunneling Microscopy

Cited by 3 publications

References 134 publications

Enhanced Bonding of Silver Nanoparticles on Oxidized TiO2(110)

Enhanced Bonding of Silver Nanoparticles on Oxidized TiO2(110)

Tunable Photoelectrochemical Properties by Nanostructural Control in WO3 Thin Films Prepared by Carboxylic Acid-Assisted Electrodeposition

Unraveling the Water Oxidation Mechanism on a Stoichiometric and Reduced Rutile TiO2 (100) Surface Using First-Principles Calculations

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Product

Resources

About

Enhanced Bonding of Silver Nanoparticles on Oxidized TiO₂(110)

Enhanced Bonding of Silver Nanoparticles on Oxidized TiO₂(110)

Tunable Photoelectrochemical Properties by Nanostructural Control in WO₃ Thin Films Prepared by Carboxylic Acid-Assisted Electrodeposition

Unraveling the Water Oxidation Mechanism on a Stoichiometric and Reduced Rutile TiO₂ (100) Surface Using First-Principles Calculations