Photocatalytic degradation of Orange G on nitrogen-doped TiO 2 catalysts under visible light and sunlight irradiation

Abstract

In this paper, the degradation of an azo dye Orange G (OG) on nitrogen-doped TiO 2 photocatalysts has been investigated under visible light and sunlight irradiation. Under visible light irradiation, the doped TiO 2 nanocatalysts demonstrated higher activity than the commercial Dugussa P25 TiO 2, allowing more efficient utilization of solar light, while under sunlight, P25 showed higher photocatalytic activity. According to the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectra analyses, it was found that both the nanosized anatase structure and the appearance of new absorption band in the visible region caused by nitrogen doping were responsible for the significant enhancement of OG degradation under visible light. In addition, the photosensitized oxidation mechanism originated from OG itself was also considered contributing to the higher visible-light-induced degradation efficiency. The effect of the initial pH of the solution and the dosage of hydrogen peroxide under different light sources was also investigated. Under visible light and sunlight, the optimal solution pH was both 2.0, while the optimal dosage of H 2O 2 was 5.0 and 15.0 mmol/l, respectively.