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Carbon-doped TiO 2 micro-/nanospheres and nanotubes have been synthesized via a single source chemical vapor deposition in an inert atmosphere. Organic compound Ti(OC 4 H 9 ) 4 was used as the titanium, oxygen, and carbon source, while argon served as the carrier gas. The effect of the temperature, substrate, and the flow rate of the carrier gas is investigated. The diameter of the formed carbon-doped TiO 2 spheres can be adjusted from 100 nm to several micrometers by varying the flow rate of the carrier gas. The as-prepared TiO 2 nanotubes are highly ordered with a diameter of about 100 nm and a wall thickness of around 15 nm. The estimated optical band gap is 2.78 eV for the formed carbon-doped TiO 2 microspheres and 2.72 eV for the synthesized carbon-doped TiO 2 nanotubes, both of which are much smaller than that of bulk anatase TiO 2 (3.20 eV). The photocurrent of the carbon-doped TiO 2 spheres is much higher than that of commercial P-25, which is currently considered as one of the best TiO 2 photocatalysts, especially under visible light irradiation. The possible mechanism of the formation of TiO 2 spheres and nanotubes is also discussed.
Wu et al. (Wed,) studied this question.