Coupled semiconductor systems for photocatalysis.: Preparation and characterization of polycrystalline mixed WO3/WS2 powders

Mixed WO(3)/WS(2) powders were prepared by oxidation of WS(2). The physical properties of the samples were characterized by X-ray diffraction, diffuse reflectance-spectroscopy, and scanning electron microscopy; they were strongly dependent upon the time and temperature of oxidation. The chemical state and the elemental distribution of the sample surface were investigated by X-ray photoelectron spectroscopy. The photocatalytic results have showed that the aqueous suspensions of the mixed WO(3)/WS(2) systems have significantly higher activities than pure WS(2) and WO(3) for the photodegradation of phenol. The enhanced performance can be related to the presence of heterojunctions WO(3)/WS(2) On the single particles. The best results were obtained when the surface WS2 molar fraction was about 0.5.