Combustion Synthesis And Doping Of Titanium Dioxide

A novel combustion technique was used for the preparation and doping of titanium dioxide (TiO2). This metal oxide of titanium is a large band gap semiconductor (3.0 - 3.2 eV) that primarily absorbs in the ultraviolet region of the electromagnietic spectrum. However, the combustion synthesized TiO2 (CS-TiO2) prepared here, presented a shift in the absorption of light to the visible region of the spectrum and a high photocatalytic activity toward the reduction of Cr(VI). The final product was characterized using X-ray powder difraction (XRD), difuse reectance spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Comparison to a commercial TiO2 (P-25 from Degussa) benchmark sample was used in each case. Difuse reflectance spectroscopy showed an optical bandgap as low as 2.5 eV in the case of cationic doping with sulfur (present as a mixture of 4+ and 6+ states) and 1.7 eV in the case of co-doping with molybdenum. XPS studies showed doping and co-doping of the host oxide in each case precluding possible doping by carbon or nitrogen. An increase in the photocatalytic activity of this semiconductor toward the reduction of hexavalent chromium under visible light was achieved. Combustion synthesis opens up a wide range of synthetic possibilities of oxide semiconductors because of its low energy requirement and simplicity.