N-TiO2: Chemical Synthesis and Photocatalysis

The chemical synthesis of nitrogen-doped titanium dioxide (N-TiO2) is explored in an attempt to understand the mechanisms of doping. Urea is used as precursor in a sol gel synthesis of N-TiO2. Chemical and structural changes during thermal treatment of the precursors were followed by several techniques. The effect of doping on band gap, morphology, and microstructure was also determined. The byproducts produced during firing correspond to those obtained during urea thermal decomposition. Polynitrogenated colored compounds produced at temperatures below 400 degrees C may act as sensitizer. Incorporation of N in the TiO2 structure is possible at higher temperatures. Degradation experiments of salicylic acid under UVA and visible light (lambda> 400 nm) in the presence of TiO2 or N-TiO2 indicate that doping decreases the activity under UVA light, while stable byproducts are produced under visible light.