Photocatalytic performance of chromium or nitrogen doped arc ion plated-TiO2 films

Titanium dioxide is currently used as a photocatalyst, due to its semiconductive nature, however its relatively high band gap means that it is only effective when exposed to UV light. It has been found that the addition of a third element to TiO2 can not only improve its photocatalytic activity with UV irradiation but also extend its use into the visible region of the electromagnetic spectrum. In this study, metallic chromium and nonmetallic nitrogen doping elements are independently incorporated into titanium dioxide films, which are deposited by arc ion plating. The morphology, microstructure, chemical state and light absorbance of the doped films are investigated. The photocatalysis-induced decolorization of methylene blue aqueous solution is determined by a UV–Visible spectrometer to assess the changes in photocatalytic activity of the titanium dioxide deposits with the addition of the third element, film structure and light absorbance. Experimental results show that the amount of anatase phase in the deposit is decreased by doping TiO2 with nitrogen or chromium. At 30 wt.% chromium and a nitrogen partial pressure of 50% the deposits are seen to be X-ray amorphous. The chromium doped films resulted in the light absorbance shifting to the visible range. Doping with chromium and nitrogen generally led to a reduction in photocatalytic efficacy, however at the lowest nitrogen partial pressures, of 5–10% in oxygen, it is increased.