A study of the electronic structure and reactivity of V/TiO2(110) with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS)

Lee, Sungwon; Zając, G.; Goodman, D. W.

doi:10.1007/s11244-006-0077-7

Cited by 12 publications

(19 citation statements)

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“…An adsorption of an electron donor species may reduce it, leading to the oxidation degree ?III. There are experimental investigations of the interface between firstrow transition metal atoms and TiO 2 (110) [19][20][21][22][23][24][25][26][27]. These studies indeed indicate the possibility of a charge transfer from the metal to the Ti cations in agreement with theoretical results [28,29].…”

Section: Introductionsupporting

confidence: 70%

“…In the cases of Ni and Cu, the bridge site is the only stable position; optimization starting from h led to b. h site was proposed for the alkali metals [54,55]. The h site was also recently found as the preferred adsorption site in the cases of V and Fe [19,23]. For some atoms, the interaction energies are very close for both cases.…”

Section: Computational Detailsmentioning

confidence: 99%

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First-row transition metal atoms adsorption on rutile TiO2(110) surface

et al. 2012

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We performed periodic DFT calculations for adsorption of metal atoms on a perfect rutile TiO 2 (110) surface (at low coverage, h = 1/3) to investigate the interaction of an individual metal atom with TiO 2 and to compare it with a study previously done on MgO(100). We considered partial period of Mendeleev's table from K to Zn. The overall evolution of the adsorption energies shows two maxima as for MgO (100). Two main differences, however, exist: the adsorption energy is much stronger and the first maximum is enhanced relative to the second one. This is attributed to the reducibility of the surface titanium cation. When the adsorbed metal is electropositive, it is oxidized under adsorption transferring electrons to titanium cations. We present the effect of introducing a Hubbard term to the gradient-corrected approximation band-structure Hamiltonian (GGA ? U). The introduction of a reasonable Hubbard correction preserves the trends and allows localizing the electron of the reduction on Ti atoms in the near surface region. Finally, our results conclude that for heavier M atoms of the period, insertion is energetically favored relative to adsorption.

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Section: Introductionsupporting

confidence: 70%

Section: Computational Detailsmentioning

confidence: 99%

First-row transition metal atoms adsorption on rutile TiO2(110) surface

et al. 2012

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“…Studies addressing V / r-TiO 2 (110) have revealed a strong interaction between V and the support both at sub-monolayer and full-monolayer (ML) coverages [22], [24], [31], [32]. It was found that V oxidizes and TiO 2 reduces upon V deposition [21], [23], [24], [30], [33], [35]. It should be noted that the highest V oxidation state in these studies is lower than +5.…”

Section: Introductionmentioning

confidence: 77%

“…It should be noted that the highest V oxidation state in these studies is lower than +5. Because of the importance of the V 5+ oxidation state, numerous studies have aimed at a characterization of the VO x / TiO 2 system under various oxidation conditions [20], [22]- [25], [33], [35]. Two oxidation methods have been applied most frequently, namely post-oxidation (V deposition in UHV and subsequent oxygen exposure) and reactive evaporation (V deposition in an oxygen background).…”

Section: Introductionmentioning

confidence: 99%

“…Two oxidation methods have been applied most frequently, namely post-oxidation (V deposition in UHV and subsequent oxygen exposure) and reactive evaporation (V deposition in an oxygen background). Reactive evaporation results in the growth of V 2 O 3 overlayers [22]- [24], [35], whereas postoxidation mainly results in VO 2 or mixtures of V 2 O 3 and VO 2 [20], [23]- [25], [33], [35].…”

Section: Introductionmentioning

confidence: 99%

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Coverage-dependent oxidation and reduction of vanadium supported on anatase TiO2(1 0 1)

Koust

Reinecke

Adamsen

et al. 2018

Journal of Catalysis

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Using a multi-technical approach, we studied the oxidation of anatase TiO 2 (101)-supported vanadium (V) clusters at room temperature. We found by ex situ XPS that the highest oxidation state is +4 at sub-monolayer coverage regardless of the O 2 pressure, and STM studies revealed that the initial oxidation proceeds through oxygen-induced disintegration of V clusters into monomeric VO 2 species. By contrast, for ~2 monolayer V coverage, a partial oxidation to V 5+ is achieved. By in situ APXPS measurements, we found that V can be maintained in the V 5+ oxidation state irrespective of the coverage; however, in the sub-monolayer range, an O 2 pressure of at least ~1 × 10-5 mbar is needed. Our results suggest an enhanced reducibility of V in direct contact with the TiO 2 support compared to V in the 2 nd layer, which is in line with the observed optimum V 2 O 5 loading in catalytic applications just slightly below a full monolayer.

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Evidences for Different Reaction Sites for Dehydrogenation and Dehydration of Ethanol over Vanadia Supported on Titania

Kim

Ryu

2019

Bulletin Korean Chem Soc

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Vanadia supported on titania were prepared with increasing vanadia loadings up to 20 wt % to study the effect of the vanadia loading on catalytic reactivity. A competitive decomposition of ethanol into ethylene (dehydration) and acetaldehyde (dehydrogenation) over the catalyst occurs over the vanadia supported on TiO 2 . Dehydrogenation is generally favored over dehydration over a wide range of the vanadia loadings up to 20 wt % due to a lower energy barrier for the dehydrogenation channel. Both dehydration and dehydrogenation rates are enhanced in proportion to the vanadia loadings up to about 2 wt %. At higher vanadia loadings (>2 wt %), however, the dehydration rate decreases while the dehydrogenation rate saturates. X-ray photoelectron spectroscopic analysis reveals that reduced V and Ti species are formed at the low vanadia contents and act as strong dissociative adsorption sites for H 2 O, while extended VO x clusters as well as three-dimensional V 2 O 5 islands formed at high vanadia loadings prevent the formation of such sites. Thus, the observed difference between the two reaction channels can be explained from the structural transition of the vanadia overlayers from highly dispersed small VO x clusters into larger polyvanadates or islands. At low vanadia loadings (<2 wt %), both the edge sites and the surface sites of the small VO x clusters grow in proportion to the loadings as the number of the clusters increases. Thus, both reaction channels are enhanced as well. At higher vanadia loadings (>2 wt %), however, the transformation into larger islands reduces the edge sites or the boundaries between the clusters and TiO, not the surface area. This implies that the active sites for the dehydrogenation are on the surfaces of the vanadia overlayers, while those for the dehydration are on the boundaries between the VO x and TiO 2 . Our results provide an additional insight into the active sites for dehydration and dehydrogenation reactions over the titania-supported vanadia catalysts.

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A study of the electronic structure and reactivity of V/TiO2(110) with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS)

Cited by 12 publications

References 31 publications

First-row transition metal atoms adsorption on rutile TiO2(110) surface

First-row transition metal atoms adsorption on rutile TiO2(110) surface

Coverage-dependent oxidation and reduction of vanadium supported on anatase TiO2(1 0 1)

Evidences for Different Reaction Sites for Dehydrogenation and Dehydration of Ethanol over Vanadia Supported on Titania

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A study of the electronic structure and reactivity of V/TiO2(110) with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS)

Cited by 12 publications

References 31 publications

First-row transition metal atoms adsorption on rutile TiO2(110) surface

First-row transition metal atoms adsorption on rutile TiO2(110) surface

Coverage-dependent oxidation and reduction of vanadium supported on anatase TiO2(1 0 1)

Evidences for Different Reaction Sites for Dehydrogenation and Dehydration of Ethanol over Vanadia Supported on Titania

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Coverage-dependent oxidation and reduction of vanadium supported on anatase TiO2(1 0 1)