Titanium oxide photocatalysis

Harada, M., Honda, M., Yamashita, H., and Anpo, M., 1999, Preparation of titanium oxide photocatalysis loaded on activated carbon and their photocataiytic reactivity for the degradation of 2-propatiol diluted in water. Research on Chemical Intermediates, 25(8) 757-768. 

Chen H, Nanayakkara CE, Grassian VH (2012) Titanium oxide photocatalysis in atmospheric chemistry. Chem Rev 112 5919-5948... 

Asahi, R., Morikawa, T., Ohwaki, T., Aoki, K., and Taga, Y. (2001) Visible-light photocatalysis in nitrogen-doped titanium oxides. Science, 293 (5528), 269-271. 

Kato H, Hori M, Konta R, Shimodaira Y, Kudo A (2004) Construction of Z-scheme type heterogeneous photocatalysis systems for water splitting into H2 and O2 under visible light irradiation Chem Lett 33 1348-1349 Asahi R, Morikawa T, Ohwaki T, Aoki K, Taga Y (2001) Visible light photocatalysis in nitrogen-doped titanium oxide. Science 293 269-271... 

When titanium oxides are irradiated with UV light that is greater than the band-gap energy of the catalyst (about X < 380 nm), electrons (e ) and holes (h+) are produced in the conduction and valence bands, respectively. These electrons and holes have a high reductive potential and oxidative potential, respectively, which, together, cause catalytic reactions on the surfaces namely photocatalytic reactions are induced. Because of its similarity with the mechanism observed with photosynthesis in green plants, photocatalysis may also be referred to as artificial photosynthesis [1-4]. As will be introduced in a later section, there are no limits to the possibilities and applications of titanium oxide photocatalysts as environmentally harmonious catalysts and/or sustainable green chemical systems. ... 

Nitroaromatics also sensitize the oxidation of methylarenes and it has been found that silica-grafted 2,4,6-trinitrobenzene is a convenient heterogeneous sensitizer, giving the aldehydes in 79-90% yields with 100% selectivity [229]. Bibenzyls, pinacols and pinacol ethers are likewise oxidized to ketones or respectively esters through carbon-carbon bond fragmentation upon dicyanonaphthalene sensitization [230]. A good method for benzylic oxidation is based on titanium dioxide photocatalysis [231-233]. 

Yang, T. S., Yang, M. C., Shiu, C. B., Chang, W. K. and Wong, M. S. (2006). Effect of N2 ion flux on the photocatalysis of nitrogen-doped titanium oxide films by electron-beam evaporation. Appl. Surf. Sci. 252(10), 3729-3736. 

In catalyzed photolysis either the catalyst molecule (Fig. 5-11, situation B) or the substrate molecule (Fig. 5-11, situation C), or both, are in an electronically excited state during the catalytic step. The electronically excited catalyst molecule is produced via photon absorption by a nominal catalyst (Fig. 5-11, situation B). The reaction of substrate to product is catalytic with, respect to the concentration of the electronically excited catalyst species. It is non-catalytic in photons and therefore, continuous irradiation is required to maintain the catalytic cycle. The quantum yield of product formation Product is equal to or less than unity. Titanium dioxide photocatalysis is the most widely applied example of this type, with Ti02 representing the nominal catalyst that must be electronically excited by photon absorption with formation of the electron hole pair Ti02 (hvb + cb), being the active catalytic species (cf Fig. 3-17 and Fig. 5-9, reaction 1). The oxidation of substrates by the combination of UV/VIS radiation and an appropriate photocatalyst is often called photocatalytic oxidation (PCO). 

Asahi R, Morikawa T, Ohwaki T, Aoki k, Taga Y. Visible-Light photocatalysis in nitrogen-doped titanium oxides. Science 2001 283 269-271. 

Let us finally turn to a brief discussion of the third term, Ti02 (i.e., titanium dioxide). Ti02 has three different crystal structures [18] rutile, anatase, and brookite only the former two of them are commonly used in photocatalysis. Like for many other metal oxides (also for titanium oxide) have the respective structural, optical, and electronic properties... 

Titanium oxide Titanium dioxide with the nominal composition Ti02 is a semiconductor with a band gap of 3.2 e V it exists in three different crystalline modifications, two of which (anatase and rutile) are commonly employed in photocatalysis. 

Anpo, M. (1997) Photocatalysis on titanium oxide catalysts Approaches in achieving highly efficient reactions and realizing the use of visible light. Catal. Surv. Jpn., 1, 169—179. 

Keywords Highly dispersed oxides Photocatalysis Polyoxotungstates Selective oxidations Titanium dioxide... 

Wan L, Li J, Feng J, Sim F, Mao Z. Improved optical response and photocatalysis for N-doped titanium oxide films prepared by oxidation of TiN. Appl Surf Sci 2007 253 4764-7. 

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