Infra-red study of the surface properties of rutile. Water and surface hydroxyl species

Jackson, P.; Parfitt, G. D.

doi:10.1039/tf9716702469

Cited by 123 publications

(57 citation statements)

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“…Every other Si atom on the (111) surface of b-crystoballite is terminated by an OH group. 30,32 In the case of TiO 2 , the rutile phase exhibits predominantly (110) planes 33,34,35,36,37 and in the case of ZrO 2 , the (101) planes are the most stable planes. 38,39 For both TiO 2 and ZrO 2 , each support atom can be connected to a hydroxyl group.…”

Section: Theoretical Methodsmentioning

confidence: 99%

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

2002

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Density functional theory was used to investigate the mechanism and kinetics of methanol oxidation to formaldehyde over vanadia supported on silica, titania, and zirconia. The catalytically active site was modeled as an isolated VO 4 unit attached to the support. The calculated geometry and vibrational frequencies of the active site are in good agreement with experimental measurements both for model compounds and oxidesupported vanadia. Methanol adsorption is found to occur preferentially with the rupture of a V-O-M bond (M = Si, Ti, Zr) and with preferential attachment of a methoxy group to V. The vibrational frequencies of the methoxy group are in good agreement with those observed experimentally as are the calculated isobars. The formation of formaldehyde is assumed to occur via the transfer of an H atom of a methoxy group to the O atom of the V=O group. The activation energy for this process is found to be in the range of 199-214 kJ/mol and apparent activation energies for the overall oxidation of methanol to formaldehyde are predicted to lie in the range of 112-123 kJ/mol, which is significantly higher than that found experimentally. Moreover, the predicted turnover frequency (TOF) for methanol oxidation is found to be essentially independent of support composition, whereas experiments show that the TOF is 10 3 greater for titania-and zirconia-supported vanadia than for silica-supported vanadia. Based on these findings, it is proposed that the formation of formaldehyde from methoxy groups may require pairs of adjacent VO 4 groups or V 2 O 7 dimer structures.3

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Section: Theoretical Methodsmentioning

confidence: 99%

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

2002

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“…The IR spectrum of OH groups in the parent TiO 2 shows band at 3,402 cm -1 . This peak was assigned to isolated surface hydroxyl groups [24,25]. The band intensity of the free hydroxyl groups increases with Mo content and the wave number shifts to higher frequencies from 3,402 to 3,436 cm -1 .…”

Section: Ftir Absorption Analysismentioning

confidence: 99%

Characterization of Mo Doped TiO2 and its Enhanced Photo Catalytic Activity Under Visible Light

2008

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Transition metal doping into the TiO 2 lattice can expand the response of these metal oxide nano particles to the visible region. In view of this, Mo 6+ ion is doped into the TiO 2 lattice in order to understand the mechanism of its photo response. The prepared photocatalysts were characterized by X-ray diffraction, UV-Visible absorption spectroscopy, UV-Visible diffuse reflectance spectroscopy, SEM, EDX, FTIR and BET specific surface area techniques. The characterization results have confirmed the incorporation of metal ions into TiO 2 lattice. XRD analysis shows no change in crystal structure except a slight variation in crystallite size and elongation along the c-axis with increase in the concentration of the dopant. Diffuse reflectance measurements showed a shift in the band edge position to longer wavelengths and an extension of the absorption to the visible region. The photo degradation efficiencies of these catalysts were studied with Tebuconazole pesticide as model pollutant. Under UV light, undoped catalyst showed higher activity than doped catalyst. But in the case of visible light irradiation Mo doped TiO 2 with intermediate dopant concentration of 0.06 atom % had the highest photocatalytic reactivity. This may be due to the narrowing of band gap so that it could effectively absorb the light of longer wavelength. The degradation path way was followed by UV-Visible spectroscopy.

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“…1,39,40 The difference between them is whether OH interacts with adjacent OH groups via hydrogen bonding. According to previous infrared studies, the absorption frequencies of isolated OH groups on TiO 2 surfaces are always higher than those of H-bonded OH groups.…”

Section: Types Of Surface Oh Groups On Tiomentioning

confidence: 99%

Structure–activity relationship of surface hydroxyl groups during NO₂ adsorption and transformation on TiO₂ nanoparticles

Liu

et al. 2017

Environ. Sci.: Nano

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The role of hydroxyl groups (OH) is significant in understanding the surface reactions on oxides. Here we combined spectroscopic experiments and theoretical calculations to reveal the role of OH in the heterogeneous reactions of NO 2 on TiO 2 nanoparticles with various crystal structures. The interaction between OH and NO 2 was determined to be a critical step, giving rise to the formation of surface HNO 3 . HNO 3 was found to be either a stable product on amorphous TiO 2 , or an important intermediate of nitrate on anatase due to its further reaction with nearby OH. The lack of surface OH on rutile limited its reactivity toward NO 2 . This study presents clear evidence that the reactivity of TiO 2 toward NO 2 greatly depends on the surface OH as well as the crystalline form. Considering the ubiquitous presence of TiO 2 nanoparticles in catalysts and in natural environments, our results could provide insights helpful to future research in both environmental catalysis and atmospheric chemistry.

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Infra-red study of the surface properties of rutile. Water and surface hydroxyl species

Cited by 123 publications

References 0 publications

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

Characterization of Mo Doped TiO2 and its Enhanced Photo Catalytic Activity Under Visible Light

Structure–activity relationship of surface hydroxyl groups during NO₂ adsorption and transformation on TiO₂ nanoparticles

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Infra-red study of the surface properties of rutile. Water and surface hydroxyl species

Cited by 123 publications

References 0 publications

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

A Density Functional Theory Study of the Oxidation of Methanol to Formaldehyde over Vanadia Supported on Silica, Titania, and Zirconia

Characterization of Mo Doped TiO2 and its Enhanced Photo Catalytic Activity Under Visible Light

Structure–activity relationship of surface hydroxyl groups during NO2 adsorption and transformation on TiO2 nanoparticles

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Structure–activity relationship of surface hydroxyl groups during NO₂ adsorption and transformation on TiO₂ nanoparticles