| Semiconductor photocatalysis is an emerging technology of clean and sustainable development that effectively employ solar energy.Its particular advantages make it rifely available in many fields.But the conversion efficiency of solar energy is restricted because originally broadband gap semiconductor omlu respond to uv light.In recent years,researchers have turned their attention to the development of photocatalysts that respond to visible light.Graphite carbon nitride?g-C3N4?had advantages such as simple preparation,visible-light-induced,stability about structure and properties,nontoxicity and appropriate band edge potentials,which received extensive attention of researchers.However,the high recombination efficiency of photogenerated electron-hole pairs,which could reduce the photoactivity,and the low adsorption capacity about g-C3N4 are disadvantages for the photocatalytic applications of them.Diversity modification which combine doped heterogeneous atomic and deposited precious metal is an efficient method to improve the photocatalytic properties of the material.In this study,we fabricated g-C3N4 and S-C3N4 by directly heating melamin and thiourea respectively.The microstructure and optical properties of the samples were studied by means of X-ray diffraction?XRD?,infrared spectroscopy?FT-IR?,transmission electron microscope?TEM?,X-ray photoelectron spectroscopy?XPS?,UV–Vis diffuse reflection spectroscopy?DRS?and photoluminescence?PL?emission spectroscopy.The effects of different doping elements on g-C3N4 catalysts were investigated by photodegradation of Rhodamine B?RhB?under visible light irradiation,and the optimum conditions for S-C3N4 photocatalytic reaction were determined.The main research contents and achievements are as follows:?1?The g-C3N4 and S-C3N4 catalysts were prepared by high temperature sintering.In the case of known the photocatalytic activity of g-C3N4 can be improved by doped with sulfur.Comparative study on two kinds of catalysts for kinetics of adsorption,adsorption thermodynamics,isothermal adsorption and the function of the group.The process of adsorption and catalytic reaction mechanism of interface is given.The optimum conditions for the reaction of S-C3N4 were obtained by designing orthogonal experiments?10 g/mL,50mL,0.4g,40min,35 oC?.?2?The Au nanoparticles with particle size of 2-20 nm was evenly distributed on S-C3N4 surface by dipping reduction method.We studied the photo-degradation kinetics of Au/S-C3N4 composite catalysts with different loads.When the load was 2 wt%,the photocatalytic activity of the sample was the highest,and the degradation rate was nearly 1 times highter than that of S-C3N4.In addition,the photocatalytic mechanism of the Au/S-C3N4 composite catalyst was analyzed.?3?We studied the photo-degradation kinetics of B-S-C3N4 catalysts.The photocatalytic performance of g-C3N4 was significantly improved by the co-doping of boron sulfur,and B-S-C3N4degradation rate was 0.07878 min-1,which was twice as high as S-C3N4,and 10 times as much as g-C3N4.The improvement of the photocatalytic performance is attributed to the co-doping of two heterogeneous elements.Because the increase of electron hole in the compound center by the defect of single doping can be mended.In addition,the configuration and electron structure of various doping catalysts are studied by density functional theory,and the synergistic effect of heterogeneous elements in the degradation process is analyzed... |
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