Titanium oxide visible light

Keywords Hydrogen Iron oxide Mixed metal oxides Titanium dioxide Visible-light activation... 

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. 

Wu, P., Xie, R., Imlay, J.A., and Shang, J.K. (2009) Visible-light-induced photocatalytic inactivation of bacteria by composite photocatalysts of palladium oxide and nitrogen-doped titanium oxide. Applied Catalysis B Environmental,... 

FIGURE 8.12. The speculated mechanism for the stoichiometric splitting of water with visible light using tungsten oxide and titanium oxide. Note the stair-step mechanism. From Sayama et al. 

Liu H, Gao L (2004) (Sulfur, Nitrogen)-codoped rutile-titanium oxide as a visible-light-activated photocatalyst. J Am Ceram Soc 87 1582-1584... 

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... 

Fig. 9 Rate of hydrogen generation from nanotube arrays films of different lengths annealed at 530 °C. Electrode area of 1 cm 100 mW/cm visible light. In the inset FESEM cross-sectional image of 2.8 um long Xi02 nanotube array prepared by anodic oxidation of a titanium foil in an electrolyte containing potassium fluoride (KF 0.1 M), sodium hydrogen sulfate (1 M), trisodium citrate (0.2 M) and sodium hydroxide. Elaborated from Grimes et...

However, unlike photosynthesis in green plants, the titanium oxide photocatalyst does not absorb visible light and, therefore, it can make use of only 3-4% of solar photons that reach the Earth. Therefore, to address such enormous tasks, photocatalytic systems which are able to operate effectively and efficiently not only under ultraviolet (UV) but also under sunlight must be established. To this end, it is vital to design and develop unique titanium oxide photocatalysts which can absorb and operate with high efficiency under solar and/or visible-light irradiation [9-16]. 

This chapter deals with the design and development of such unique second-generation titanium oxide photocatalysts which absorb UV-visible light and operate effectively under visible and/or solar irradiation by applying an advanced metal ion-implantation method. 

With unimplanted or chemically doped titanium oxide photocatalysts, the photocatalytic reaction does not proceed under visible-light irradiation (X > 450 nm). However, we have found that visible-light irradiation of metal ion-implanted... 

It was also found that increasing the number (or amounts) of metal ion implanted into the deep bulk of the titanium oxides caused the photocatalytic efficiency of these photocatalysts to increase under visible-light irradiation, passing through a maximum at around 6 X 10 ions/cm of the catalyst, then decreas-... 

Figure 10 Effect of the depth profile of V ions in the V-ion-implanted titanium oxide photocatalyst on their photocatalytic reactivity for the decomposition of NOx under visible light (X > 450 nm) irradiation at 295 K.

The ESR spectra of the V-ion-implanted titanium oxide catalysts were measured before and after calcination of the samples in O2 at around 723-823 K, respectively (Fig. 11). Distinct and characteristic reticular V" ions were detected only after calcination at around 723-823 K. It was found that only when a shift in the absorption band toward visible-light regions was observed, the reticular V ions could be detected by ESR. No such reticular V ions or shift in the absorption band have ever been observed with titanium oxides chemically doped with V ions [16,18,19]. 

Furthermore, as shown in Fig. 10.2, such red shifts in the absorption band of the metal ion-implanted titanium oxide photocatalysts can be observed for any kind of titanium oxide except amorphous types, the extent of the shift changing from sample to sample. It was also found that such shifts in the absorption band can be observed only after calcination of the metal ion-implanted titanium oxide samples in 02 at around 723-823 K. Therefore, calcination in 02 in combination with metal ion-implantation was found to be instrumental in the shift of the absoiption spectrum toward visible light regions. These results clearly show that shifts in the absorption band of the titanium oxides by metal ion-implantation is a general phenomenon and not a special feature of a certain kind of titanium oxide catalyst. 

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