Visible light photocatalytic properties and thermochromic phenomena of nanostructured BiOCl microspheres

Black nanostructured BiOCl microspheres were directly synthesized by a hydrothermal method. The black ball-like BiOCl microspheres and black flower-like BiOCl microspheres were obtained using different surfactant. The color of the BiOCl microspheres turned from black to white when being annealed at 400°C in air for 3h and could be recovered to black by exposure to ultraviolet light for a few hours. The photocatalytic activity of both the black and the white BiOCl microspheres was characterized by the photo-degradation of methyl orange dye under visible light irradiation. The black ball-like nanostructure BiOCl displayed the best photocatalytic activity, compared with the white BiOCl and the black flower-like BiOCl. It can degrade the methyl orange dye to 20% within 70min under visible light irradiation. The high activity of the BiOCl ball-like sphere may own to its special morphology, strong absorption in visible light range and the existence of oxygen vacancies.