Nitrogen-substituted TiO2: investigation on the photocatalytic activity in the visible light range
2009
Tessier, Franck | Zollfrank, Cordt | Travitzky, Nahum | Windsheimer, Hans | Merdrignac-Conanec, Odile | Rocherullé, Jean | Greil, Peter
Nitrogen-doped titanium oxides are attractive materials for the degradation of organic pollutants in water due to their photocatalytic activity in the visible light range. The evolution of the photocatalytic properties was studied on a number of TiOₓNy powder samples where x varied from 2 to 0 (TiO₂ to TiN) through increasing the nitrogen content (y = 0–1). X-ray diffraction and Raman spectroscopy showed that an anatase type TiOₓNy was obtained at low nitrogen contents (<2 wt%). With increasing nitrogen content a structural transition from anatase to cubic TiN was observed. Electron spin resonance measurements of the TiOₓNy samples confirmed the presence of unpaired electrons and defects for the TiOₓNy materials with low nitrogen content (<2 wt%). The photo-induced activity of the TiOₓNy materials was evaluated under VIS illumination of solutions containing methylene blue as an organic probe. The TiOₓNy samples exhibited an improved photocatalytic activity under visible light illumination compared to TiO₂ at nitrogen levels lower than 2 wt%. A photocatalytic activity could not be detected at nitrogen levels higher than 10 wt% and after conversion of the TiOₓNy into the cubic phase. Optimum photocatalytic activity in the visible range can be achieved at nitrogen levels lower than 2 wt% for TiOₓNy materials.
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