Synthesis of black TiO2 with efficient visible-light photocatalytic activity by ultraviolet light irradiation and low temperature annealing

Herein, a simple, efficient, and environmentally friendly strategy to prepare black TiO2 nanoparticles has been reported; the procedure combines the ultraviolet light irradiation and low-temperature annealing (300 degrees C) with continuous N-2 flow under atmospheric pressure. The samples were characterized by the various techniques, such as X-ray diffraction, high resolution transmission electron microcopy, Raman spectroscopy, X-ray photoelectron spectroscopy. The photocatalytic degradation of the organic contaminant Rhodamine B was investigated when black TiO2 nanoparticles was irradiaed with ultraviolet light and visible light. The black TiO2 material possesses an anatase phase and is able to absorb a high amount of photon energy in the visible light region, effectively driving photochemical degradation reactions. The enhancement of the photocatalytic activity can be attributed to the following: first, the hydrogen ions decrease the localized Ti3+ states (which are also the e(-)-h(+) recombination centers) leading to a more efficient separation of the electron-hole pairs; secondly, the conduction band electrons in black TiO2 nanoparticles are responsible for strong absorption of visible light. Consequently, the photocatalytic degradation of Rhodamine B can be significantly enhanced using black TiO2 nanoparticles. This work proves that hydrogenated black TiO2 promotes the absorption of the entire electromagnetic spectrum and exhibits high photocatalytic activity under solar light irradiation.