Über die Chemie der Oberfläche des Titandioxids. IV. Austausch von Hydroxidionen gegen Fluoridionen

Herrmann, Michael; Kaluza, U.; Boehm, H. P.

doi:10.1002/zaac.19703720307

Cited by 49 publications

(42 citation statements)

References 7 publications

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“…In presence of fluoride, it is supposed a simple exchange equilibrium as indicated below, where A and B indicate the acidic and basic sites, respectively. Fluoride ion replaces the basic hydroxyls, indicated as B, (as confirmed by IR and XPS spectroscopy [25,26]) according to the above reaction for which an equilibrium constant k 1 = 8 × 10 -7 has been reported [27], and coordinates the surface-bound titanium atoms directly.…”

Section: Surficial Charge and Distribution On Tio 2 And Tio 2 /Fmentioning

confidence: 97%

Photocatalytic transformation of organic compounds in the presence of inorganic ions

Calza

Pelizzetti

2001

Pure and Applied Chemistry

116

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The influence of halide ions on the photocatalytic process on titanium dioxide has been investigated carefully. Chloride and bromide ions, acting as hole scavengers, generate active radical species (e.g., ·Cl and ·Br) that participate in reactions with the organic compounds and the transient intermediates. Chloride and bromide ions have shown to deeply inhibit the degradation rate of chloroform and tetrachloromethane and to modify both the qualitative and quantitative distribution of their intermediates formed during the degradation process. In the presence of bromide, CBrCl3 is detected as intermediate during CCl4 degradation, while in the presence of chloride, formation of CCl4 is observed in the CHCl3 degradation. Fluoride ions, differently from the other halides, cannot be oxidized by the valence hole and may be used as a diagnostic tool in mechanistic studies. The influence of fluoride on phenol has been investigated, and, by choosing appropriate experimental conditions, it was possible to evaluate the role of the different active species in the photocatalytic process.

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Section: Surficial Charge and Distribution On Tio 2 And Tio 2 /Fmentioning

confidence: 97%

Photocatalytic transformation of organic compounds in the presence of inorganic ions

Calza

Pelizzetti

2001

Pure and Applied Chemistry

116

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“…The C element is ascribed to residual carbon. The fluoride peak at binding energy 684.5 eV (F 1s) only appears in the F-TiO 2 sample, indicating the formation of surface fluoride ( Ti-F) by a ligand exchange reaction between F − and the surface hydroxyl group on the TiO 2 surface [40][41][42][43][44]. No peak for F − ions in the lattice at 688.5 eV was observed in the spectra, because the hydrothermal process could prevent the substitution of F − for O 2− in the lattice of TiO 2 [21,39,40,45].…”

Section: Xps Analysismentioning

confidence: 99%

Photocatalytic oxidation of gaseous ammonia over fluorinated TiO2 with exposed (001) facets

et al. 2014

Applied Catalysis B: Environmental

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a b s t r a c tA surface-fluorinated TiO 2 (F-TiO 2 ) catalyst was synthesized by a hydrothermal method using hydrofluoric acid (HF) solution as a capping agent, and defluorinated TiO 2 (D-TiO 2 ) was next obtained by washing the F-TiO 2 with NaOH solution. The as-prepared catalysts were tested for the photocatalytic oxidation (PCO) of gaseous NH 3 under UV light. The F-TiO 2 catalyst exhibited remarkable activity for NH 3 removal, about twice as high as that of the commercial catalyst P25. In contrast, D-TiO 2 showed an obvious decrease in PCO activity. The catalysts were characterized by X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) adsorption analysis, High-resolution Transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS). The results showed that the surface fluorination process formed the surface Ti-F group and also increased the percentage of reactive (0 0 1) facets to about 50%; the surface defluorination removed the fluorine (F) element from the F-TiO 2 surface but showed no influence on the percentage of reactive (0 0 1) facets. By comparing the specific activities of the catalysts, we found that both the active (0 0 1) facets and the surface Ti-F group contributed to the improvement of the PCO activity, while the surface Ti-F group plays the dominant role. The Ti-F group could retard the recombination of photogenerated electrons and holes, which is possibly the major reason for the excellent activity of the F-TiO 2 catalyst.

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“…Surface fluorination of TiO 2 (F-TiO 2 ) is a simple ligand exchange between fluoride anions (F À ) and surface hydroxyl groups on TiO 2 in water: 57 Ti-OH + F À = Ti-F + OH À ; pK F E 6.2 (ref. 57) where the notation Ti-X (X = OH or F) represents surface species.…”

Section: Adsorption Sites At Anatase (100) In the Aqueous Phasementioning

confidence: 99%

Adsorption of oxalate on anatase (100) and rutile (110) surfaces in aqueous systems: experimental results vs. theoretical predictions

Mendive

Bredow

Feldhoff

et al. 2009

Phys. Chem. Chem. Phys.

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A combined experimental and theoretical study of the adsorption of oxalic acid from the aqueous phase at the surface of anatase nanoparticles has been performed. The interfaces were investigated by ATR-FTIR measurements and quantum-chemical calculations using the semiempirical method MSINDO. The vibration spectra of the most stable surface complexes have been calculated and used for the interpretation of experimental results. The theoretical studies have been done using the anatase (100) surface to model the adsorption of oxalic acid and water. The effect of interaction of water and oxalic acid on the adsorption mechanism and the vibration spectra was taken into account in the theoretical models. Inclusion of solvation effects was found crucial to determine the type of denticity and structure of adsorbed complexes. By comparison of experimental data and theoretical calculations the most likely surface species and the effects of hydration in their relative stabilities were determined. The present results are compared to previous studies preformed also by combination of experimental and theoretical calculations of analogous systems using nanoparticulate rutile [C. B. Mendive et al., Phys. Chem. Chem. Phys., 2008, 10, 1960, ref. 1]. Differences between surface complexes on anatase and rutile lie mainly on the denticity type. Whilst in the case of rutile the most stable species consist of two bidentate surface complexes followed in third place by a monodentated form, anatase allows the formation of four species in which the stability order is reversed with respect to the denticity type. In the case of anatase, the main contributors to the surface speciation are two monodentate species differing in the position of the H atom within the molecule (being more stable when it is placed in the O-C-O moiety not bound to the surface); and two bidentate species, one deprotonated and one monoprotonated, in which the C-C bond was parallel or perpendicular to the TiO2 surface, respectively.

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Über die Chemie der Oberfläche des Titandioxids. IV. Austausch von Hydroxidionen gegen Fluoridionen

Cited by 49 publications

References 7 publications

Photocatalytic transformation of organic compounds in the presence of inorganic ions

Photocatalytic transformation of organic compounds in the presence of inorganic ions

Photocatalytic oxidation of gaseous ammonia over fluorinated TiO2 with exposed (001) facets

Adsorption of oxalate on anatase (100) and rutile (110) surfaces in aqueous systems: experimental results vs. theoretical predictions

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