Platinum-titanium dioxide

That products of intermediate oxidation level can be detected in the photocatalytic reactions of hydrocarbons and fossil fuels is also consistent with a surface bound radical intermediate . Photocatalytic isotope exchange between cyclopentane and deuterium on bifunctional platinum/titanium dioxide catalysts indicates the importance of weakly adsorbed pentane at oxide sites. The platinum serves to attract free electrons, decreasing the efficiency of electron-hole recombination, and to regenerate the surface oxide after exchange. Much better control of the exchange is afforded with photoelectrochemical than thermal catalysis > ) As before, hydrocarbon oxidations can also be conducted at the gas-solid interface... 

Baker R.T.K., Kim K.S., Emerson A.B., Dumesic J.A. (1986) A Study of the Platinum-Titanium Dioxide System for the Hydrogenation of Graphite Ramifications of Strong Metal-Support Interactions, J. Phys. Chem. 90(5), 860-866. 

Aromatic hydrocarbons can be oxidatively cleaved either on a side chain or in the ring (Eq. 6) [60]. Even saturated hydrocarbons can be induced to become oxygenated or to participate in isotope exchange on irradiated platinum/ titanium dioxide catalysts [151, 155, 156]. Competitive trapping of the photogenerated conduction band electron by adsorbed protons is thought to be responsible for the reduced contribution of oxygen at lower pH. 

The second form consists of Pt metal but the iridium is present as iridium dioxide. Iridium metal may or may not be present, depending on the baking temperature (14). Titanium dioxide is present in amounts of only a few weight percent. The analysis of these coatings suggests that the platinum metal acts as a binder for the iridium oxide, which in turn acts as the electrocatalyst for chlorine discharge (14). In the case of thermally deposited platinum—iridium metal coatings, these may actually form an intermetallic. Both the electrocatalytic properties and wear rates are expected to differ for these two forms of platinum—iridium-coated anodes. 

Titanium Dioxide Single-Crystal and Powder Surfaces in the Presence and Absence of Platinum... 

Kowalska, E., Remita, H., Colbeau-Justm, C., Hupka, J., and BelloniJ. (2008) Modification of titanium dioxide with platinum ions and dusters application in photocatalysis. Journal of Physical Chemistry C, 112 (4), 1124-1131. 

B. Kraeutler, A.J. Bard, Heterogeneous photocatalytic preparation of supported catalysts. Photodeposition of platinum on titanium dioxide powder and other substrates, /. Am. Chem. Soc. 100 (1978) 4317-4318. 

Fujishima and Honda reported the splitting of water by the use of a semiconductor electrode of titanium dioxide (rutile) connected through an electrical load to a platinum black counter-electrode. Irradiation of the Ti02 electrode with near-UV light caused electrons to flow from it to the platinum counter-electrode via the external circuit. 

Smooth platinum, lead dioxide and graphite are anode materials commonly used in electrooxidation processes. All show large overpotentials for oxygen evolution in aqueous solution. Platinum coated titanium is available as an alternative to sheet platinum metal. Stable surfaces of lead dioxide are prepared by electrolytic oxidation of sheet lead in dilute sulphuric acid and can be used in the presence of sulphuric acid as electrolyte. Lead dioxide may also be electroplated onto titanium anodes from lead(Il) nitrate solution to form a non-porous layer which can then be used in other electrolyte solutions [21],... 

Borgarello E, Serpone N, Emo G, Harris R, Pelizzetti E, Minero C (1986) Light-induced reduction of rhodium (III) and palladium (II) on titanium dioxide dispersions and the selective photochemical separation and recovery of gold (III), platinum (IV) and rhodium (III) in chloride media. Inorg Chem 25 4499-4503... 

Cao et. al. also examined titanium dioxide photocatalysts doped with 0.5% platinum. These doped catalysts displayed complete activity recovery following thermal regeneration at 350°C. Presumably, the addition of platinum, which may act as a thermal oxidation catalyst, allows for the destruction of accumulated intermediates generated during the photocatalytic oxidation at lower temperatures than untreated titanium dioxide. 

It has recently been recognized that crystal structure and particle size can also influence photoelectrochemical activity. For example, titanium dioxide crystals exist in the anatase phase in samples which have been calcined at temperatures below 500 °C, as rutile at calcination temperatures above 600 °C, and as a mixture of the two phases at intermediate temperature ranges. When a range of such samples were examined for photocatalytic oxidation of 2-propanol and reduction of silver sulfate, anatase samples were found to be active for both systems, with increased efficiency observed with crystal growth. The activity for alcohol oxidation, but not silver ion reduction, was observed when the catalyst was partially covered with platinum black. On rutile, comparable activity was observed for Ag, but the activity towards alcohol oxidation was negligibly small . Photoinduced activity could also be correlated with particle size. 

Electropolyraerization is useful and has been successfully applied to 4-vinylpyridine complexes and to 4-methyl-4 -vinyl-2,2 -bipyridyl.52 Vinylferrocene (vide infra) has been polymerized on to platinum, glassy carbon and titanium dioxide electrodes by introduction to a radiofrequency argon plasma discharge. Electropolymerization and plasma polymerization are likely to be of value to produce copolymers on electrode surfaces. 

At the end of 1960 s, Honda and Fujishima found that in a photochemical cell employing titanium dioxide and platinum electrodes, irradiation of the titanium dioxide electrode resulted in splitting of water into hydrogen and oxygen (18,19). This work has had an extraordinarily strong impact for the research on the photochemical action of various semiconductors inducing evolution of hydrogen from water as well as new catalytic reactions (20). 

Highfield JG, Pichat P. Photoacoustic study of the influence of platinum loading and bulk doping with chromium III ions on the reversible photochromic effect in titanium dioxide, correlation with photocatalytic properties. New J Chem 1989 13 61-66. 

Macyk W, Kisch H. Mechanism of titanium dioxide photosensitization by platinum(IV)chloride surface complexes. / Inf Rec 2000 25 435-8. 

Macyk W, Kisch H. Photosensitization of crystalline and amorphous titanium dioxide by platinum(IV) chloride surface complexes. Chem Ear J 2001 7 1862-7. 

The electrocatalytic behavior of olefins was studied by Zanta et al. (2000) at thermally prepared ruthenium-titanium- and iridium-titanium-dioxide-coated anodes. The aliphatic olefins were shown to be inactive in the region before oxygen evolution, while aromatic ones showed one or two oxidation peaks, and the catalytic activity seemed to be the same for both substrates. However, as for platinum anodes, voltammetric studies and FTIR analyses have also shown the formation of a polymeric film that blocks the surface of the electrode and decreases its activity. 

Reactions of titanium(IV) ions To study these reactions use a 0-2m solution of titanium(IV) sulphate, which is prepared either by dissolving the reagent [Ti(S04)2] in 5 per cent sulphuric acid, or by fusing titanium dioxide TiOz with a 12—15 fold excess of potassium pyrosulphate in a porcelain or platinum crucible. 

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