| After the industrial revolution,the rapid development of human science and technology have been creating unprecedented achievements.With the continuous development of the world economy,fossil fuel has become one of the major energy sources.However,the burning of fossil fuels will bring serious environmental problems,such as acid rain,fog and haze,global warming and so on.In recent years,a kind of semiconductor photocatalytic material,graphitic carbon nitride（g-C3N4）,has attracted more and more attention of scholars.g-C3N4 is a stable,inexpensive,nonmetallic photocatalytic material with a special electronic band structure（2.7e V）,induced by its excellent chemical stability,it is widely used in the fields of photocatalysis,such as water pollution,water photolysis for oxygen and hydrogen generation,air purification and so on.The band gap of g-C3N4 is low,the photocatalytic reaction can be carried out when g-C3N4 is under the irradiation of natural light resources,thus,the pollutants can be degraded into non-toxic and harmless substances.For pollutants in the air,such as NOx,it can be eventually degraded to NO3-and NO2-by g-C3N4,so that the final degradation product is washed away by water.In this paper,the research background and research status of g-C3N4 are discussed in depth,and the features of producing g-C3N4 with different raw materials under various preparation conditions are explored,by comparing the yields and the photocatalytic performances of g-C3N4 prepared from various raw materials under different preparation conditions under the irradiation of metal halide lamp,a reliable method for the preparation of g-C3N4 is determined.By analyzing the properties differences in g-C3N4 prepared by various methods,the causes of their different photocatalytic performances are analyzed.Then,this article also explores the methods of attaching g-C3N4 to cement concrete,which will be helpful in the future to applying g-C3N4 in road engineering to degrade air pollutants.The main research contents and results of this article are as follows:（1）g-C3N4 was prepared from urea,thiourea,dicyandiamide and melamine by high-temperature calcinations.The degradation ratio of NO was tested to explore the optimum conditions for the preparation of g-C3N4.Considering the factors of photocatalytic activities and yields of g-C3N4,a reliable method for preparing g-C3N4 was established.The results showed that the g-C3N4 prepared by calcination of melamine at 500 ℃ for 4 hours owned the best photocatalytic activity with high yields.Therefore,melamine pyrolyzed at 500 ℃ for 4 hours was confirmed as a reliable method to produce g-C3N4.（2）The photocatalytic degradation mechanism of NO by g-C3N4 was revealed by various characterization methods and structural analysis.By observing the differences in chemical compositions and microstructures of g-C3N4 prepared from various raw materials and conditions,the reasons for the differences in photocatalytic properties of various g-C3N4 were revealed.It was found that the photocatalytic performance of g-C3N4 was influenced by the polycondensation degree of g-C3N4,the content of melem,the specific surface area,the absorption intensity of light,the energy of band gap,and so on.Compared with other factors,the content of melem had a greater impact on the photocatalytic performance of g-C3N4.（3）In order to explore the method of applying g-C3N4 to road engineering to degrade NOx,the photocatalytic concrete was prepared by combining g-C3N4 with cement concrete block.The results showed that the photocatalytic concrete prepared by directly attaching g-C3N4 to the surface of cement concrete had a better photocatalytic activity.It was found that the main factors affecting the activity of photocatalytic concrete were the attaching amount of g-C3N4 and the surface area of cement concrete block. |
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