Self-cleaning and anti-bacterial activities of the photo-catalyst titanium dioxide make it a superior compound for use in the ceramics and glass industry. In order to achieve high self-cleaning efficiency for building products, it is important that Titania is present as anatase phase. Moreover, it is desirable that the particle sizes are in Nano-range, so that a large enough surface area is available for enhanced catalytic performance. In the present paper, Cobalt and Nickel co-doped (4%mol Ni and 4%mol Co doped TiO2) and un-doped TiO2 Nano powders have been prepared by sol–gel technique. They were calcined at the temperatures in the range of 475–1075 C. Ni/Co co-doped TiO2 postponed the anatase to rutile transformation of TiO2 by about 200–300C, such that before calcination at 775C, no rutile was detected for 4 mol% Ni/Co co-doped TiO2. A systematic decreasing on crystallite size and increasing on specific surface area of Ni/Co co-doped TiO2 were observed. Photo-catalytic activity of anatase polymorph was measured by the decomposition rate of methylene blue under visible light. The results showed enhanced catalysis under visible light for Ni/Co co-doped TiO2 as compared to pure TiO2. The enhanced performance was attributed to surface chemistry change associated with a slight shift in the band gap. Depending on the temperatures ranging from 475 to 1075 C, band gap energy of Ni and Co doped TiO2 crystals decreased. For all samples there is a general reduction of the band gap energy from 3.00 to 2.96 eV.
