Novel porous Ag2S/ZnS composite nanospheres: Fabrication and enhanced visible-light photocatalytic activities

Elimination of toxic organic compounds from wastewater is a longstanding challenge in the fields of environmental science, especially, under the visible-light irradiation. Here we present a facile design to fabricate novel porous Ag2S/ZnS composite nanospheres via a hydrothermal procedure followed by a cation exchange method. Field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray energy-dispersive spectroscopy (EDS), and UV-vis spectroscopy were used to characterize the crystallinity, morphology, structure and properties of the composite nanospheres. The photocatalytic performance was evaluated by the photocatalytic decolorization of methyl orange in aqueous solution under visible light irradiation. Results show that the composite nanospheres exhibited enhanced visible light photocatalytic activity compared with the initial porous ZnS nanospheres. Among them, sample of Ag(0.4)Zna(0.8)S gave the highest degradation rate of about 96% under visible-light irradiation within 15 min. The enhanced photocatalytic activity was presumed to result from the direct photoinduced interfacial charge transfer (IFCT) from the valence band (VB) of ZnS to Ag2S, due to the intimate contact between ZnS and Ag2S, the porous structure, and the appropriate composition ratio of porous Ag2S/ZnS composite. The present method could be extended to fabricate a large number of semiconductor composites for catalysis and solar cells based on the difference of the solubility products. (C) 2015 Elsevier B.V. All rights reserved.