Development of new photocatalytic materials sensitive to visible light irradiation has attracted increasing interests because of the importance of effective utilization of the solar energy and indoor illumination. Although many efforts have been directed to the development of visible-light-sensitive photocatalysts, by modifying TiO2, or by developing new materials, the practical applications are still restricted, mainly owing to the limited option of catalysts and to the still low photocatalytic activities.
Up to now, we have focused our concerns on the development of new photocatalysts, by controlling crystal and electronic structures of oxide semiconductors. We have reported various new materials, such as: (In1-xNix)TaO4, CaBi2O4, CaMoO4-BiVO4, AgNbO3-NaNbO3 solid solutions, NaBiO3, [1-3], etc., for photocatalytic water splitting, or photocatalytic degradation of organics contaminats.
In this talk, we will report the preparation and characterization of new Nb-containing oxide photocatalysts. The new photocatalysts can effectively decompose various volatile organic compounds, such as acetaldehyde, 2-propanol, etc, under irradiation of weak visible light (0.01 mW/cm2) emitting from blue-light-emitting diodes (400< wavelength <550 nm). Designing guidelines and future prospects for development of new photocatalytic materials will also be discussed, basing on systematic studies on the materials syntheses, photophysical properties, and photocatalytic activities of these new photocatalysts, obtained by various experimental measurements and theoretical calculations.

[1] Z. Zou, J. Ye, K. Sayama and H. Arakawa, Nature, 414, 625(2001).
[2] J. Tang, Z. Zou, J. Ye, Angew. Chem. Int. Ed., 43, 4463 (2004).
[3] T. Kako, Z. Zou, M. Katakiri, J. Ye, Chem. Mater., 19(2), 198, 2007.