A flame aerosol method has been employed to prepare spherical TiO2 nano-particle photocatalysts with controlled anatase/rutile phase ratios without calcination at higher temperatures. This method was found to have important advantages since the main factors in achieving high photocatalytic activity such as the particle size, crystallinity and the anatase/rutile phase ratios could be easily controlled. In particular, the incorporation of small amounts of bimetals, such as Fe and Zn, were found to initiate the formation of well-crystalline, small and uniform spherical nano-size particles with a well-defined anatase/rutile phase ratio of around 60/40, similar to P-25 TiO2. This suppressed the recombination of the photoformed charge carriers leading to a significant increase in the photocatalytic reactivity of the TiO2 nano-particles. The incorporation of very small amounts of mono-metals, such as Fe, Cr and Zn (around 1 at.%), within the TiO2 nano-particles led to a slight increase in the photocatalytic activity of the TiO2 nano-particle photocatalysts for the complete oxidation of 2-propanol dissolved in water into CO2 and H2O as compared with the unincorporated pure TiO2. The incorporation of bimetals of Fe and Zn within TiO2 (Fe/Zn–TiO2) nano-particles, on the other hand, led to a remarkable enhancement in the photocatalytic activity as compared with the unincorporated and mono-metal incorporated TiO2.
TiO2 photocatalysts Flame aerosol method Incorporation of bimetals Complete photocatalytic oxidation of 2-propanol
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The authors would like to thank both KIST and the Japan Society for the Promotion of Science (JSPS) for their financial support.