Remarkable enhancement of the TiO2 photocatalyst activity under visible light by doping sulfur for dye photodecolorization

Abstract

To enhance the photoactivity of TiO2 under visible light, doping TiO2 by sulfur atoms from sulfuric acid has been conducted by hydrothermal method, where the concentration of the acid is varied (25, 50, and 100 mmol/L) to obtain the doped TiO2-S with various S content. The doped photocatalysts obtained are characterized by using X-ray diffraction, ultraviolet specular reflectance spectrophotometer, Fourier transform infrared, and transmission electron microscope machines. The activity of the doped photocatalyst has been examined for Congo-red photo-decolorization under visible light, via batch experiment. The research results assigned that the doping sulfur into TiO2 has successfully narrowed the gap that resulted in the remarkable enhancement of the activity under visible light in the Congo red decolorization. The enhancement is influenced by S content in the photocatalyst and the highest activity is shown by TiO2-S prepared from 50 mmol/L sulfuric acids. The efficiency of the Congo-red photo-decolorization catalyzed by TiO2-S (50) is found to be controlled by reaction time, photocatalyst weight, and solution pH. By applying 50 mg of the photocatalyst weight in 50 mL of the dye solution with pH 7, within 60 min, the highest photo-decolorization of 10 mg/L Congo-red, that is 87% could be reached.