Infra-red Spectra of Polar Molecules adsorbed on Titanium Dioxide Pigments

Smith, I. Trevor

doi:10.1038/201067a0

Cited by 21 publications

(3 citation statements)

References 3 publications

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“…Figure shows a series of spectra in the υ(OH) region for adsorbed CH 3 CN on TiO 2 at different temperatures. The broad band at ∼3440 cm -1 corresponds to the associated OH groups on the surface while the bands at 3728, 3677, and 3608 cm -1 correspond to the different types of isolated OH groups on the surface. , The interaction between the adsorbed CH 3 CN and the surface OH groups increases with increasing temperature above 126K as CH 3 CN diffuses into the porous TiO 2 powder. The difference spectra of Figure clearly show that with increasing temperature the intensity of the isolated OH bands decreases and that of the associated OH bands increases.…”

Section: Resultsmentioning

confidence: 98%

Adsorption and Photooxidation of CH₃CN on TiO₂

1999

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The adsorption and photooxidation of CH3CN chemisorbed on TiO2 has been investigated using infrared spectroscopy. It was found that CH3CN forms an ice layer on TiO2 at 126K and above 126K CH3CN diffusion into TiO2 occurs. At 200K, the adsorption of CH3CN on both isolated Ti−OH groups and on the Ti4+ Lewis acid site was observed. Under UV irradiation (350 ± 50 nm; hυ = 3.10−4.13 eV), CH3CN was oxidized in the presence of O2 to form H2O, CO2, surface CO3 2- and an intermediate partially oxidized isocyanate species, NCO, which was identified by various isotopic experiments. Photooxidation of the CH3 moiety in adsorbed CH3CN occurs more readily does the CN moiety in CH3CN. Lattice oxygen of TiO2 was found to preferentially form adsorbed NCO, compared to oxygen from adsorbed O2. A mechanism of the formation of NCO species was postulated.

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Section: Resultsmentioning

confidence: 98%

Adsorption and Photooxidation of CH₃CN on TiO₂

1999

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“…There is no OH-0 bond in the undisturbed lattice that correlates with the observed infra-red stretching frequency, suggesting that the hydroxyl groups are attached to the titanium cations. Smith (1964) has examined the absorption of organic groups by titanium dioxide pigments with the conclusion that the surface is negatively charged. If the negative charge is attached to the surface hydroxyl group, then charge balance is achieved with the cation in its normal Ti4+ state.…”

Section: Nature Of Diffusing Speciesmentioning

confidence: 99%

The effect of hydrogen on the electrical properties of rutile

Hill

1968

J. Phys. D: Appl. Phys.

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Hydrogen in rutile has two influences on the electrical properties: Verneuil crystals contain hydrogen compensating the trivalent impurities. Excess hydrogen acts as an electron donor, thereby increasing the conductivity. Removal of hydrogen above 650°C in vacuum causes structural changes accompanied by enhanced conductivity and dielectric loss. There is also a change in the activation energy for diffusion at this temperature. Values of the coefficient of diffusion of protons in the temperature range 450-800°C in crystals of differing impurity content are presented. The position of the hydrogen, in the basal plane of the rutile lattice, is confirmed by the dichroism of the absorption. Weight-loss experiments suggest that hydrogen leaves the crystal in combination with oxygen in the proportions required to form water.

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“…Meanwhile, with a weaker basicity compared to ammonia molecules, acetaldehyde (is considered as a ''neutral'' compound in this study) may adsorb on the oxide surface forming a weaker sorption. Smith [20] has shown that carboxylic acids are adsorbed either by hydrogen bonding of the carboxyl group or by proton transfer to the TiO 2 surface. As it is reasonable to consider that the carbonyl group of the acetaldehyde also behaves as that in carboxylic acid, both compounds have comparable Lewis basicity.…”

Section: Adsorption Analysismentioning

confidence: 99%

Kinetic analysis on photocatalytic degradation of gaseous acetaldehyde, ammonia and hydrogen sulfide on nanosized porous TiO₂films

Sopyan¹

2007

Science and Technology of Advanced Materials

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The characteristics of the UV illumination-assisted degradation of gaseous acetaldehyde, hydrogen sulfide, and ammonia on highly active nanostructured-anatase and rutile films were investigated. It was found that the anatase film showed a higher photocatalytic activity than the counterpart did, however, the magnitude of difference in the photocatalytic activity of both films decreased in the order ammonia4acetaldehyde4hydrogen sulfide. To elucidate the reasons for the observation, the adsorption characteristics and the kinetics of photocatalytic degradation of the three reactants on both films were analyzed. The adsorption analysis examined using a simple Langmuir isotherm, showed that adsorbability on both films decreased in the order ammonia4acetaldehyde4hydrogen sulfide, which can be explained in terms of the decreasing electron-donor capacity. Acetaldehyde and ammonia adsorbed more strongly and with higher coverage on anatase film (1.2 and 5.6 molecules/nm 2 , respectively) than on rutile (0.6 and 4.7 molecules/nm 2 , respectively). Conversely, hydrogen sulfide molecules adsorbed more strongly on rutile film (0.7 molecules/nm 2 ) than on anatase (0.4 molecules/nm 2 ). Exposure to UV light illumination brought about the photocatalytic oxidation of the three gases in contact with both TiO 2 films, and the decrease in concentration were measured, and their kinetics are analyzed in terms of the Langmuir-Hinshelwood kinetic model. From the kinetic analysis, it was found that the anatase film showed the photocatalytic activities that were factors of $8 and $5 higher than the rutile film for the degradation of gaseous ammonia and acetaldehyde, respectively. However, the activity was only a factor of $1.5 higher for the photodegradation of hydrogen sulfide. These observations are systematically explained by the charge separation efficiency and the adsorption characteristics of each catalyst as well as by the physical and electrochemical properties of each reactant. r

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Infra-red Spectra of Polar Molecules adsorbed on Titanium Dioxide Pigments

Cited by 21 publications

References 3 publications

Adsorption and Photooxidation of CH₃CN on TiO₂

Adsorption and Photooxidation of CH₃CN on TiO₂

The effect of hydrogen on the electrical properties of rutile

Kinetic analysis on photocatalytic degradation of gaseous acetaldehyde, ammonia and hydrogen sulfide on nanosized porous TiO₂films

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Infra-red Spectra of Polar Molecules adsorbed on Titanium Dioxide Pigments

Cited by 21 publications

References 3 publications

Adsorption and Photooxidation of CH3CN on TiO2

Adsorption and Photooxidation of CH3CN on TiO2

The effect of hydrogen on the electrical properties of rutile

Kinetic analysis on photocatalytic degradation of gaseous acetaldehyde, ammonia and hydrogen sulfide on nanosized porous TiO2films

Contact Info

Product

Resources

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Adsorption and Photooxidation of CH₃CN on TiO₂

Adsorption and Photooxidation of CH₃CN on TiO₂

Kinetic analysis on photocatalytic degradation of gaseous acetaldehyde, ammonia and hydrogen sulfide on nanosized porous TiO₂films