Photocatalytic activities of N-doped nano-titanias and titanium nitride
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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ABSTRACT: Hydrogen production by water splitting is a holy grail of science, being one route to a non-fossil fuel and a potential source of clean energy. It is essential to use a non-polluting energy source to drive the reaction and one way is to utilise sunlight energy, combined with a way to overcome the kinetic limitations of the reaction. The production of hydrogen by the photocatalytic cleavage of water can overcome these energetic hurdles. This area of science is briefly reviewed here, focussing on two routes, namely i) the use of sacrificial agents such as alcohols to act as oxygen scavengers and liberate hydrogen only and ii) by direct water splitting to produce both hydrogen and oxygen. The factors which are important in determining the characteristics of effective photocatalytic water splitting systems are elucidated.Green Chemistry 08/2011; 13(9). DOI:10.1039/C1GC00022E · 6.85 Impact Factor
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