Fabrication of g-C3N4/SnS2/SnO2 nanocomposites for promoting photocatalytic reduction of aqueous Cr(VI) under visible light

A kind of g-C3N4/SnS2/SnO2 nanocomposite was firstly prepared by solvothermal method at 140 degrees C for 4 h after 30 min ultrasonic irradiation. X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR), transmission electron microscopy (TEM) and electrical/optical testing techniques confirmed that the oxygen atoms in SnO2 might be doped in the g-C3N4 in the synthesizing process, resulting to a good combination of SnS2/SnO2 nanosheets and g-C3N4 nanoparticles by Sn-O-C bond, which would have an influence on the light adsorption, carriers transfer, and electron-hole separation efficiency of g-C3N4/SnS2/SnO2. Additionally, the ultrasonic assisted solvothermal reaction could also promote the formation of oxygen vacancies on the surface of the material, which leads to the up-shift of valence band. The photocatalytic properties of the g-C3N4/SnS2/SnO2 were studied by the reduction of aqueous Cr(VI). The data clearly indicated that the photocatalytic activity of as-synthesized composites depends on their compositions, and reaction rate constant of Cr(VI) on the composite-C (with the mass ratio of 1: 3) with visible light (lambda > 420 nm) driven can be improved 41.7-and 4.0-time compared with pure g-C3N4 and SnS2/SnO2, respectively. Additionally, more than 90% lost photocatalytic activity of composite-C can be regenerated by water-washing and drying treatment. The present study provided an efficient method for removing toxic Cr(VI) ions via photoreduction utilizing visible light irradiation (lambda > 420 nm).