Titania, TiO

Figure 16.11 Titania (TiO c)-suppoited (a) and niobium-doped titania (Nbo.o8Tio.920j /Au)-suppoited (b) Au particle-size-dependent specific activities for—CO oxidation at a potential step of 0.5 V vs. RHE. The current densities have been corrected for the TEM-deteimined...

Single oxides Alumina (AI Oj) ZirConia (ZrO ) Titania (TiO ) Magnesium oxide (MgO) Silica (SiOj)... 

The most common process for producing large quantities of titanium diboride is by reacting titania (TiO ) with carbon and boron carbide (B C) or boron sesquioxide (B Oj) as follows ... 

Above the ZPC of titania, the hydroxyls groups of tiiis compound tend to be negatively charged by formation of the deprotonated titania (TiO ) spedes. So that it is relatively difficult for de tungsten ions to be adsorbed on the titania surface, due to the electrostatic repulsions in the solution. Below the ZPC, on the alumina the surface is charged poritively, therefore, tungsten aiuons tend to be adsorbed on die alumina surface. 

Fig. 20.19 Particle/aggregate size populations as a function of pH solution during nanocrystalline titania (TiO ) synthesis by controlled hydrolysis. The bars represent the range. Insertion shows the images of pH 7 Ti02 aggregate deposits in microchannel pores (Adapted from Dunphy Guzman et al. 2006, Copyright 2006 American Chemical Society)...

Janus, M., M. Toyoda, M. Inagaki, B. Tryba, and A.W. Morawski, Preparation of TiOj/C photocatalyst by ethanol modification of hydrolysed titania TiO(OH)2 in a pressure reactor. J. Adv. Oxid. Tech. 10 (2007) 260-266. 

Hosseini-Sarvari M, Safary E (2011) Nano-sulfated titania (TiO) as a new solid acid catalyst for Friedel-Crafts acylation and Beckman rearrangement in solvent-free conditions. J Sulfur Chem 32(5) 463 73... 

Ti surface modified in oxygen-containing environments forms titania (TiO ), which was used in a nanosized form for decorating Ti nanotubes. This material showed good cytocompatibility (Huo et al., 2014), antibacterial properties, and greater stem cell osteogenic capacity (Mozaffarian et al., 2015). The addition of BMP-2 into Ti implants stimulated heahng and facilitated the formation of the characteristic bone tissue structures (Pavlova et al., 2014 Wen et al., 2016). 

Combinatorial chemistry techniques were used recently to synthesize and automatically test libraries of supported gold nanoparticles as electrocatalysts for CO oxidation. Hayden et al. [59,79] used physical vapor deposition to prepare a range of gold nanoparticles of mean diameter less than 6.5 nm on titania (TiO x 1.96) and carbon supports which were subsequently tested with regard to CO oxidation activity in acid solution (other authors [93] synthesized a range of Au nanoparticles on TiO using pulsed cathodic electrodeposition). It was observed that, under potential sweep conditions, CO oxidation in the positive sweep, at particles of mean diameter 2.8 nm, commenced at... 

Figure 16.7 Specific activity for oxygen reduction at 0.3 V vs. RHE on carbon- and titania-supported Au nanoparticles [Guerin et al., 2006b] (a) C/Au (b) TiO /Au. In the case of TiO c/Au (b), results are shown for data obtained on arrays of electrodes (O) and on rotating disk electrodes (RDE) (A).

In order to obtain high conversion efficiencies, optimization of the short-circuit photocurrent (z sc) and open-circuit potential (Voc) of the solar cell is essential. The conduction band of the TiO is known to have a Nernstian dependence on pH [13,18], The fully protonated sensitizer (22), upon adsorption, transfers most of its protons to the TiO surface, charging it positively. The electric field associated with the surface dipole generated in this fashion enhances the adsorption of the anionic ruthenium complex and assists electron injection from the excited state of the sensitizer in the titania conduction band, favoring high photocurrents (18-19 inA/cm ). However, the open-circuit potential (0.65 V) is lower due to the positive shift of the conduction-band edge induced by the surface protonation. 

Similarly, for TiO whose spectrum consists of two band systems, the high-frequency one corresponds to basic, i.e. single-bonded, hydroxyl groups, while the other corresponds to more acidic bridged hydroxyls. Hie anionic character of the type I hydroxyls on alumina and titania is exemplified by the fact that they preferentially exchange with fluoride ions ... 

The photochemical properties of titania surfaces are of interest for several reasons. They determine the stability of pigmented paint systems [76], the rate at which pollutants can be degraded in systems designed to purify air and water [77], and are the root cause of poorly understood phenomena such as water photolysis [78] and super hydrophilicity [79]. Using thin rutile epilayers with five low index orientations, it has been shown that the relative rates of photochemical reactions catalyzed by titania depend on the surface orientation [80]. In this chapter, experiments used to map the complete orientation dependence of the relative photochemical reactivity of TiO are described [81-83]. In this case, the relevant reactions are carried out at room temperature and this gives us the opportunity to fix both the surface morphological structure and stoichiometry. For the reactions described here, all of the surfaces were... 

Solvothermal decomposition of titanium tcrt-butoxide and titanium oxy-acetylacetonate (TiO(acac)2) in toluene at 300°C yields nanocrystalline anatase. It should be noted that the lowest temperature required for the formation of crystalline titania by CVD synthesis was reported to be 400 to 450°C. ° ° ... 

Besides alkoxides, acetylacetonates are also used as the starting materials for the synthesis of oxides. Titania (anatase) is obtained by decomposition of titanium oxyacetylacetonate (TiO(acac)2) in toluene at 300°C. Similarly solvothermal treatment of Fe(lll) acetylacetonate in toluene yields microcrystalline magnetite. One of the drawbacks of the use of acetylacetonate may be formation of various high boiling point organic by-products via aldol-type condensation of the acetylacetone. Actually more than 50 compounds are detected by gas chromatography-mass spectrometry (GC-MS) analysis of the supernatant of the reaction, some of which are phenolic compounds and are hardly removed from the oxide particles by washing with acetone. ... 

The small domain size of nanofacet supported stractures and multiple overlapping LEED patterns obtained from extended encapsulated metal films on the TiO surface significantly complicates quantitative structural interpretation. Several groups have developed techniques to grow TiO overlayers on Pt single-crystal surfaces to obtain large, well-defined titania films. Koel has performed detailed work on the Pt(lOO)... 

Rh particles supported on TiO exhibited a very different catalytic behavior. The activity was very high after reduction at 373 K, indicating a promotion of the reaction by unreduced titania. The reaction rate decreased rapidly with increasing reduction temperature until it diminished upon reduction at 723 K. Electron microscopy inspection revealed spreading and coalescence of adjoining Rh particles over the support upon reduction at >623 K (Fig. 15.6f). This indicates a change in the interfacial energy but does not explain the nearly 100-fold decrease in activity. However, for comparable experimental conditions (1 bar H, reduction between... 

TiO Overlayer Formation in Metal/Titania Model Systems... 

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