High visible-light photocatalytic activity of nitrogen-doped titania prepared from layered titania/isostearate nanocomposite

A nitrogen-doped titania photocatalyst with a high visible-light activity was synthesized from a layered titania/isostearate nanocomposite which was prepared by the sol–gel technique. Nitrogen doping was conducted by treatment with aqueous ammonia followed by calcination either in an O2 (20%)/N2 mixture or in pure N2 at various temperatures. The visible-light activity of the samples was evaluated on the basis of the decomposition rate of methylene blue (MB) in an aqueous solution with blue-light-emitting diodes (BLED; 470 nm) as the light source. The obtained samples were vivid yellow and absorbed visible light in the region of 380–500 nm. The visible-light absorbance in this region correlated with the doped-nitrogen content in the sample. On the other hand, the visible-light photocatalytic activity did not correlate with it, and was increased by the partial release of the doped nitrogen. High visible-light photocatalytic activity was observed for the 400 °C-calcined samples, which was considerably higher than the activity of the nitrogen-doped anatase titania prepared by the calcination of the hydrolysis product of Ti(SO4)2 with aqueous ammonia.