The Co-doped TiO2 powders were prepared by the sol-gel method, and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis absorption spectroscopy, and X-ray diffraction. The photocatalytic activities of the powders were also measured by using an annulus photochemical reactor. The results showed that the grain size grew gradually with calcination temperatures. When the calcination temperature grew up to 873 K, the cobalt element separated out from TiO2 as CoTiO3. At the same time, TiO2 transferred from anatase to rutile phase. In phase transfer, crystal lattice constant a, c and cell volumes of TiO2 decreased. After doping with cobalt, the photon excited wavelength of the TiO2 powder was broadened to visible light, but the photocatalytic activity of the TiO2 powder decreased obviously.

Key words: cobalt, titanium dioxide, powder, characterization