Photodegradation of organic dyes via competitive direct reduction/indirect oxidation on InSnS2 under visible light

A visible-light-responsive photocatalyst, SnS2, was prepared by a rapid microwave-assisted method. This photocatalyst showed a narrow band gap (2.0 eV) and a broad-spectrum response in the range of 400-800 nm. To enhance its photocatalytic activity, the surface of SnS2 was modified with indium-doping and loading of a noble metal. The photocatalytic activity of SnS2, InSnS2, and Pt/InSnS2 was evaluated by photodegradation of methyl orange (MO) and rhodamine B (RhB) under visible light. While direct reduction via a photoelectron was the major reaction in the degradation of MO, indirect oxidation (deethylation) via reactive oxygen species (center dot OH and center dot O-2 (-)) in the degradation of RhB was accompanied subsequently with direct reduction (cycloreversion). Therefore, photocatalytic efficiency and the mechanism for photodegradation of organic dyes depended on the types of organic dyes.