Preparation And Catalytic Performance Of Carbon Nitride/Graphdiyne Composites

Water environment problem is a common and important problem in today's society.With the continuous increase of global population and the rapid development of social economy,the problem of water pollution is becoming more and more prominent.In water bodies,the most common pollutions are endocrine disrupting substances,antibiotics and various dyes,etc.At the same time,there are a large number of pathogenic bacteria in domestic sewage.To solve this problem,although a large number of sewage treatment technologies have been put forward at home and abroad,the existing sewage treatment technologies still have many disadvantages,such as high energy consumption,toxic disinfection by-products,high production cost,complicated working procedures and so on.Photocatalytic technology,as one of advanced oxidation technologies(AOP),has been paid more and more attention in recent years.In order to maximize photocatalytic efficiency,on the one hand,appropriate photocatalyst must be selected,and on the other hand,it can be combined with other AOP technologies.As a photocatalyst material,nonmetal-based semiconductors have more advantages than metal-based semiconductors,and have attracted extensive attention because of their high stability,non-toxicity,low price and easy availability.Among them,graphite carbon nitride(g-C₃N₄)is a typical nonmetallic photocatalyst,which not only has the advantages of the above-mentioned general nonmetallic photocatalyst,but also has the characteristics of special layered structure,suitable energy band structure and excellent visible light response.At present,it has become a hot spot in photocatalytic research.However,due to its own shortcomings,such as small specific surface area,low utilization rate of visible light and high recombination rate of photo-generated carriers,its application is greatly limited.To solve the inherent problems of g-C₃N₄ monomer,low layer graphite carbon nitride/graphite(u-g-C₃N₄/GDY)heterojunction and tubular graphite carbon nitride supported boron doped graphdiyne quantum dots(B-GDQDs/TCN)composite catalyst were constructed to make up for the shortcomings of g-C₃N₄ monomer.This method can effectively overcome the shortcomings of g-C₃N₄ and improve its catalytic performance.The main work of this paper is divided into the following three parts:1.Preparation and photoelectrocatalysis of two-dimensional fewer layers graphite carbon nitride/graphdiyne metal-free heterojunction:After a few layers of g-C₃N₄nanosheets(u-g-C₃N₄)were prepared by chemical stripping method,the ultra-thin two-dimensional heterostructure material u-g-C₃N₄/GDY was obtained by in-situ growth of graphdiyne(GDY),and the u-g-C₃N₄ was modified by GDY.Compared with g-C₃N₄,the electrochemical and optical properties of u-g-C₃N₄/GDY heterojunction materials have been greatly improved.Through photoelectrocatalysis of bisphenol A to explore its catalytic performance,the degradation rate of bisphenol A can reach 100%in one hour,which is more than double that of monomer g-C₃N₄.The principle is that the introduced GDY has narrow band gap and high hole mobility,which can effectively inhibit the recombination of carriers in u-g-C₃N₄ through rapid hole transfer.At the same time,potassium persulfate(PMS)is introduced as a cocatalyst to enhance the oxidation of pollutants.Based on the above advantages,u-g-C₃N₄/GDY photocatalyst showed excellent degradation efficiency.2.Preparation and photocatalytic performance of one-dimensional tubular graphite carbon nitride supported graphdiyne quantum dots:Hollow tubular graphite carbon nitride(TCN)was prepared by hydrothermal method,and then the metal-free TCN supported B-GDQDs(B-GDQDs/TCN)nanocomposites with one-dimensional tubular structure were obtained by simple ice-assisted ultrasonic method.The special structure of g-C₃N₄ hollow tube and the loading of boron-doped graphdiyne quantum dots can promote the electron migration and charge separation efficiency of the catalyst,reduce the recombination of charge carriers,and more carriers can be used to attack BPA.At the same time,potassium persulfate(PMS)is introduced as a cocatalyst to enhance the oxidation of BPA,and its photocatalytic efficiency is obviously improved.PMS/B-GDQDs/TCN/Vis system was constructed to degrade BPA organic pollutants to determine its photocatalytic efficiency.Thanks to the above advantages,the optimized catalyst(B-GDQDs/TCN)showed excellent performance.The apparent rate constant(K_app)of BGDQDs/TCN photocatalytic degradation of BPA is 0.06344 min^-1,which is 3.31 times that of CN(0.0129 min^-1)and2.46 times that of TCN(0.01735 min^-1).3.Practical application of carbon nitride/graphdiyne composite:In order to explore the effect of catalyst in practical application,a circulating degradation flow device was built in the laboratory to simulate the degradation process of industrial wastewater.At the same time,the catalytic efficiency of the above two catalysts for degradation of various dyes,antibiotics and pathogenic bacteria was explored,and their universality in practical application was judged.The experimental results show that the two antibiotics have good degradation effects on various dyes and antibiotics used in the experiment,which can generally reach more than 80%.At the same time,they have good antibacterial effects on pathogenic bacteria,and have great application potential in practical application.