| Titanium dioxide with nanosize has been widely investigated due to its excellent performance as photocatalyst due to its unique qualities such as safety, nontoxic, high stability, lost cost and non-further pollution. It has also been widely used in the section of environment and solar energy, such as degradation the organic compounds, anti-bacteria (or virus), functional chinaware, as a pigment in the screens, paints, and solar energy battery.However, TiO2 shows photocatalytic activity only under irradiation by UV light, meaning only 5% of the solar energy can be utilized (UV light 5%, visible light 43%, and 52% infrared light), which limits its further application. Doping TiO2 seems to be the potential solutions for improving its efficiency to shift its absorption from the UV region into the visible-light. Usually, the doped element is mental element or non-mental element. When the mental element was doped into the TiO2 matrix, it will replace the position of Ti, and influence the charge carrier recombination rates as well as interfacial electron-transfer rates, which improve the photocatalyst activity of the TiO2; when the non-mental element such as N,C,S,F was doped into the TiO2 matrix, it will replace the position of O, and the doped non-mental element will narrow the bad-gap so that the photocatalyst activity of the TiO2 will improved.Carbon-doped titanium oxide nanocrystals were successfully synthesized from the use of porous resin and tetrabutyl titanate as starting materials, followed by treatment in alcohol-water solution, calcination both in N2 flow and in air. The XRD pattern shows pure phase of anatase; SEM image and surface area measurement show that the sample has similar high dispersion and large surface area to commercial photocatalyst of P25, which are attributed that the presence of porous resin in the synthesis strongly limits the aggregation of TiO2 nanocrystals. Additionally, the analysis of carbon in the samples shows that the use of porous resin results in the formation of carbon-doped TiO2 (about 1.0 %). Very importantly, photocatalytic degradation of Rhodamine-B shows that the sample exhibits higher activities than P25 under the irradiation by both visible light and UV light, which are reasonably assigned to the unique features of the sample such as carbon doping, large surface area, high crystallinity, pure phase of anatase. We also discussed the relationship between surface area, crystallinity, calcined temperature and the photocatalyst activity of TiO2 in detail.Many lanthanide ions with unique 4f electronic configuration were also doped into TiO2 in order to improve its photocatalyst activity. However, the previous reports about lanthanide-doped TiO2 are concentrate on the improving photocatalytic activity of TiO2 under the irradiation of visible light. However there still are 52% of the solar energy can not be utilized (UV light 5%, visible light 43%, and 52% infrared light). In order to improve TiO2 photocatalytic activity of TiO2 under the irradiation of NIR light, we doped Yb3+and Er3+ into TiO2.The crystal kind of TiO2 are important for its photocatalytic activity.. We discussed photocataytic activity of different crystal kind of the carbon doped TiO2 prepared by resin. It is found that the phase junction formed between the surface anatase nanoparticles and rutile particles can greatly enhance the photocatalytic activity.
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