| Since the new century,social and economic level have further been improved rapidly,environment and energy problem increasingly become a stumbling block in the course of sustainable development.Green oxidation technology has gained gradually extensive attentions in the field of environmental governance without secondary pollutants.Photocatalytic technology is such a kind of green oxidation technology.Neverthless,for the traditional photocatalyst,the lower utilization efficiency of sunlight and the higher recombination efficiency of light-induced carriers have prevented its large-scale application.Therefore,to develop a new stable broader spectral photocatalyst has become a hot spot.This paper is intended to develop the carbon nitride based composite photocatalyst with good visible-light response,strong stability,high degradation activity,and to explore the structure-peroperty relationship and the mechanism of photocatalytic reaction through the comprehensive analysis measures.In this paper,the concrete research content follows:1.The few-layer g-C3N4(flg-C3N4)was prepared by thermal polymerization and stripping method(two step calcination)using melamine as raw materials,and its layer structure was verified by characterization methods,the AFM results showed that the thickness of flg-C3N4 is 6.4 nm with about 10 layers comparing with single-layer thickness(0.64 nm);The WO3 nanorods and flg-C3N4/WO3 nanocomposites were prepared by facile solvothermal method,respectively.The phase structure,morphology,surface valence,optical properties and photocatalytic performances of photocatalysts were analyzed through comprehensive analysis means,such as X-ray photoelectron spectroscopy(XPS),electron microscope analysis(SEM,TEM),diffuse reflection spectroscopy(DRS),fluorescence spectrum(FL)and so on.The results indicted that the introduction of flg-C3N4 enhanced greatly the photocatalytic activity of WO3,the photocatalytic activity of the 20 wt%flg-C3N4/WO3 nanocomposites was 7.5 times than pure W03 and the TOC value decreased by 46.2%.Besides,the synergy mechanism between flg-C3N4 and WO3 is a major reason for its improving performance.2.In this section,MoO3 photocatalyst with a needle-like morphology and a series of flg-C3N4/MoO3 nanocomposites were synthesized and characterized.The results manifested that introduction of flg-C3N4 improved significantly the specific surface area and the photocatalytic performance of the MoO3,when the proportion flg-C3N4 was 10 wt%,the degradation efficiency of RhB came to the head(73%),the degradation efficiency of MoO3 NNs was only 38%under the same conditions.In the photocatalytic process,the photoexcited holes in the VB of MoO3 could oxide OH"into ·OH and O2was reduced into ·O2-by the photoexcited electrons in the CB of flg-C3N4,then promoted the separation efficiency of photoexcited electron-hole pairs,the participation of these active groups enhanced obviously degradation activity of pollutants.3.The flower-like ZnO was fabricated by using Zn(NO3)2·6H2O and NH3·H2O as raw material.As a result,the introduction of a certain percentage of the flg-C3N4 could increase the specific surface area of the ZnO,provide more adsorption sites and the active sites.The heterostructure between flg-C3N4 and ZnO was also conducive to the electronic transport,in addition,when the proportion of flg-C3N4 was 30 wt%,the nanocomposites under visible light region achieved the highest degradation efficiency MB(0.0025 min-1),in contrast,the kinetics constants of ZnO was only 0.0014 min-1;Besides,the degradation efficiency of 30 wt%flg-C3N4/ZnO nanocomposites was superior to pure ZnO under the UV-light irradiation region.Besides,the synergy mechanism between flg-C3N4 and ZnO is a major reason for its improving performance. |
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