Photocatalytic activities of N-doped nano-titanias and titanium nitride

Christopher Ingold Laboratories, University College London, 20 Gordon Street, London, WC1H 0AJ, UK; School of Engineering and Materials Science, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK; School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, CF10 3AT, UK; Division of Biomaterials and Tissue Engineering, UCL Eastman Dental Institute, 256 Gray's Inn Road, London, WC1X 8LD, UK
01/2009; DOI: 10.1016/j.jeurceramsoc.2009.02.008
Source: OAI

ABSTRACT TiO2 doped with various loadings of nitrogen was prepared by nitridation of a nano-TiO2 powder in an ammonia/argon atmosphere at a range of temperatures from 400 to 1100 °C. The nano-TiO2 starting powder was produced in a continuous hydrothermal flow synthesis (CHFS) process involving reaction between a flow of supercritical water and an aqueous solution of a titanium salt. The structures of the resulting nanocatalysts were investigated using powder X-ray diffraction (XRD) and Raman spectroscopy. Products ranging from N-doped anatase TiO2 to phase-pure titanium nitride (TiN) were obtained depending on post-synthesis heat-treatment temperature. The results suggest that TiN started forming when the TiO2 was heat-treated at 800 °C, and that pure phase TiN was obtained at 1000 °C after 5 h nitridation. The amounts and nature of the Ti, O and N at the surface were determined by X-ray photoelectron spectroscopy (XPS). A shift of the band-gap to lower energy and increasing absorption in the visible light region, were observed by increasing the heat-treatment temperature from 400 to 700 °C.

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