Synthesis Of Several Graphite Phase Carbon Nitride-based Semiconductor Composite Materials And Their Photocatalytic Activity

Organic dyes discharged from textile industry and other industrial processes are one of the main pollutants released to the aquatic environment.In particular,azo dyes（such as methyl orange）not only pollute the water,but also damage the ecological environment,and even have carcinogenic effects on organisms.Therefore,the removal of these dye pollutants is very important for the protection and purification of water as well as the maintenance of human and ecological environment health.Solar driven heterogeneous photocatalytic oxidation is an ideal technology for the removal of organic dyes in water.So far,a variety of visible-light-driven catalysts have been developed for degradation of organic pollutants in water environment.Among them,graphite phase carbon nitride（g-C₃N₄）has become an attractive visible light catalyst because of its high chemical activity,good stability,environmental friendliness,low cost and high photocatalytic activity.However,there are still some disadvantages in the single g-C₃N₄ photocatalysis material,such as low natural light utilization and high recombination of photocarriers.In order to improve these defects,the researchers adjusted the structure of g-C₃N₄,dope different ions and elements,modified the surface and formed multi-component heterojunction with different semiconductors etc.The results showed that these modification methods could significantly enhance the photocatalytic performance of the single g-C₃N₄photocatalyst.In view of this,this study for the first time successfully synthesized the graphite phase carbon nitride/graphene oxide（g-C₃N₄/GO）porous microsphere composite photocatalyst through the template-free low-temperature hydrothermal method,optimizing the structure of g-C₃N₄,and thus improved the photocatalytic performance.Additionally,g-C₃N₄/Cu/Cu₂O and Zn_xCd_1-xS/g-C₃N₄ multi-component graphite phase carbon nitride based semiconductor composites were successfully prepared by multi-component doping and recombination,and these composites were used for photocatalytic degradation of high concentration methyl orange（MO）solution.The results showed that the photocatalytic degradation efficiency of the composite material was significantly higher than that of the single,and the stability of the composite photocatalyst was also greatly improved.And the details are as follows:1.Using glucose and melamine as raw materials,g-C₃N₄/GO porous microsphere composite photocatalyst was for the first time successfully synthesized by template-free low temperature hydrothermal method.The results of XRD,SEM and HRTEM showed that g-C₃N₄/GO porous microspheres had a sandwich-like internal structure,which was favor for theπ-πcoupling between g-C₃N₄ and GO,promoted electron transfer and transport,expanded the natural light absorption wavelength,and enhanced the photocatalytic performance of photocatalytic materials.2.The g-C₃N₄/Cu/Cu₂O composite photocatalyst with Z-type structure was prepared through a simple static synthesis method by CuO deposition and subsequent glucose reduction on the support of g-C₃N₄.When g-C₃N₄/Cu/Cu₂O was used for the photocatalytic degradation of high concentration methyl orange solution（30mg/L）under the excitation of visible light,it was found that the degradation efficiency of methyl orange reached 86%within 3 hours,and the photocatalytic performance was stable.3.A series of Zn_xCd_1-x（0≤x≤1）solid solutions and Zn_xCd_1-xS/g-C₃N₄ composites were successfully synthesized by hydrothermal method.Under the illumination of visible light,Zn_0.3Cd_0.7S could degrade 92%of methyl orange solution（20mg/L）through three hours.When Zn_0.3Cd_0.7S was coupled with g-C₃N₄,the photocatalytic performance was further improved,and Zn_xCd_1-xS/g-C₃N₄ with the 5%loading amount of g-C₃N₄ showed the highest photocatalytic efficiency,which the degradation rate of methyl orange on the 5%g-C₃N₄/Zn_xCd_1-xS reached 98.6%through 2.5 hours.The cycle experiment of photocatalytic degradation shows that the composite photocatalyst has good chemical stability.