Preparation of photoactive nitrogen-doped rutile

An easy way of preparing highly N-doped rutile photocatalysts (N–TiO2/R) in tubular furnace in a constant ammonia (NH3) flow at 800–1000 °C temperature range is presented. New materials were compared to TiO2 samples prepared at the same temperatures in air atmosphere as well as to the starting material. Complete transformation of amorphous and anatase phases to rutile was confirmed by XRD method. Successful incorporation of relatively high amounts of nitrogen (up to 17% at.), in form of either TiO2(N), TiOxNy or TiN, on photocatalysts’ surface and in their lattice was confirmed using XPS and XRD analysis. Also presence of Ti3+ was revealed by EPR studies. In contrast to pristine TiO2, the UV–vis/DR absorption spectra of N-modified photocatalysts extended significantly into the visible light region. Whereas nitrogen concentration as well as visible light absorption were found to increase with increasing modification temperature, photocatalytic activity was, on the contrary decreasing. This may be due to the very high nitrogen concentration, obtained at higher modification temperature, as well as the presence of small amount of conductive TiN phase on the N–TiO2/1000 °C photocatalyst surface. The artificial solar light activity of new photocatalysts after thermal treatment in NH3 increased in comparison to starting material, due to nitrogen modification and presence of Ti3+ ions. Activity under UV(-vis) light, though, decreased after modification procedure, probably due to smaller surface areas of new photocatalysts and complete anatase to rutile transformation.