Preparation And Photocatalytic Study Of Surface Modification Of ZnS Nano-materials

Environmental problems have become one of the most important issues, which have affected human survival and development in the 21st century,semiconductor photocatalysis environmental pollutants has become an advanced water treatment technology recent years, so design and fabrication of efficient and stable catalysts with visible light is the key to achieving its application. Zinc sulfide (ZnS) is an important photocatalytic material; however, the larger band gap can only absorb UV light below the wavelength of 367 nm, the extensive application of ZnS nonmaterial in photocatalytic has been limited. This article is based on the problems of low solar energy utilization and low efficiency of ZnS photocatalyst, doping with Co element to improve its absorption of visible light and photocatalytic activity; the material of microstructure, surface morphology and photocatalytic properties were studied by XRD, SEM, XPS and UV-visible spectroscopy testing means.In this paper, the good crystallization, small particles uniformly distributed Co doped ZnS powders were synthesized by hydrothermal and with zinc acetate, cobalt acetate and thiourea as the raw material, discussed the different Co doping affecting on the ZnS structure, morphology and photocatalytic properties. Microstructure analysis showed that, ZnS crystal growth has existing orientation and uniform particle size. The growth characteristics and surface morphology of the grain was changed by doping with Co element, the simples have single dispersion, particle distribution and the average particle size was 200nm. High-resolution transmission electron microscopy analysis showed that the polycrystalline structure of spherical particles was composed of many small-sized nanocrystals (4nm). UV-visible spectroscopy shows that Co doped ZnS powder has red shift of absorption edge to achieve visible light response, so that its photocatalytic degradation of methyl orange solution is far superior to pure ZnS powder. After 120min light exposure by dysprosium lamp, the photocatalytic degradation efficiency was 100% with 2% Co doped ZnS, while the pure ZnS powder only been 50%.In addition, we study the impact to photocatalytic activity of Co²⁺ adsorption on the surface of ZnS power. We found that Co²⁺ adsorption on ZnS can also increase the photocatalytic properties of methyl orange, after 120min illumination, the photocatalytic efficiency can be improved almost nearly 1 time. It is easier for negatively charged adsorption of methyl orange when [Co(NH3)6]²⁺ complexes which formed from Co²⁺ adsorbed on the ZnS surface, It could also be used as a bridge that transferred electrons and holes from ZnS surface. With the help of attraction between the positively charged of [Co(NH3)6]²⁺ complexes and the charged in solution phase of methyl orange, photo-generated holes could be transferred to methyl orange molecular directly occurring on redox reaction, so that the utilization of photo-generated holes could be improved.