Preparation And Photocatalysic Performance Characterization Of Noble Metal Modified Cardon Nitride Nanorods

Environmental problems associated with organic pollutants and heavy metal ions in water have severe threat to human health.Semiconductor photocatalysis technology as an efficient and green method can effectively solve this problem.The research of photocatalytic technology focus on developing photocatalyst with visible-light-response and high electron efficiency.In recent years,carbon nitride as an organic polymer has attracted a great deal of attention due to its good visible light response,excellent photocatalytic stability and non-toxicity.To prepare carbon nitride,two methods have been chiefly developed.One is the thermal polymerization of N-containing organic compound at high temperature to prepare traditional graphite-carbon nitride(g-C3N4)bulk.However,g-C3N4 bulk exhibits low surface area and narrow visible-light absorption range(edge: ~460 nm)resulting from high degree of polycondensation of monomers.The other one is the use of solvothermal method to prepare graphite-carbon nitride(CN)nanorods.Compared with traditional g-C3N4 bulk,CN nanorods exhibit a large surface,red-shifted visible-light absorption range(edge: ~715 nm)and the greatly improved photocatalytic activity for degrading organic pollutant.However,the photocatalytic activity of CN nanorods are still limited due to the unsatisfactory photogenerated electron-hole separation efficiency and photoabsorption range.It is well knonw that the modification of semiconductor photocatalysts by noble metals(such as Au or Ag)is one of the most promising methods to overcome the low efficiency of semiconductor photocatalysis.To solove the above problems,we combine CN nanorods with noble metals nanomaterials to broaden their light response range and inhibit their photoinduced carrier recombination.The main work contents are as follows:Part 1: Firstly,the CN nanorods were prepared by solvothermal method,and then the surface of CN nanorods was decorated by Au nanoparticles(Au NPs).CN nanorods(diameters: 20-30 nm;lengths: 0.5-1 ?m)were prepared by solvothermally treating cyanuric chloride and melamine in acetonitrile solution at 180 °C for 96 h.The absorption edge of CN nanorods is about 715 nm.The surface decoration of CN nanorods by Au NPs(diameter: ~13 nm)was carried out by hydrothermally treating CN nanorods in aqueous solution of HAu Cl4 and glucose at 120 °C for 12 h.The precursor mole ratio of Au and CN nanorods are respectively 0.5:100,1:100 and 2:100,which can be recorded 0.5%Au-CN,1%Au-CN and 2%Au-CN.Compared with that of pure CN nanorods(~712 nm),the optical absorption edge of Au-CN nanorods(~790 nm)is obviously red-shifted.Under the visible light irradiation(? > 400 nm)in 120 min,all of 0.5%Au-CN,1%Au-CN and 2%Au-CN show improvement photocatalytic activity for organic pollutant degradation than pure CN nanorods.Among those,1%Au-CN exhibit the highest photocatalytic activity,it can degrade 98.2% rhodamine B,77.2% 4-chlorophenol,83.9% tetracycline and reduce 43.6% hexavalent chromium.Furthermore,the recycling tests demonstrate that Au-CN nanorods have excellent stability and cyclicity.Part 2: CN nanorods were used as substrates and different ratios of Ag/Ag Cl-CN heterojuctions were prepared by precipitation method.The precursor mole ratio of Ag/Ag Cl and CN nanorods are respectively 30:100,50:100 and 70:100,which can be recorded 30%Ag/Ag Cl-CN,50%Ag/Ag Cl-CN and 70%Ag/Ag Cl-CN.Optical properties show that the optical absorption of Ag/Ag Cl-CN heterostructure is obviously enhanced compared with that of pure Ag/Ag Cl at 400-600 nm.Under the visible light irradiation(? > 400 nm)in 100 min,all of 30%Ag/Ag Cl-CN,50%Ag/Ag Cl-CN and 70%Ag/Ag Cl-CN nanorods have enhanced of photocatalytic activity for organic pollutant degradation than pure Ag/Ag Cl.Among those,50%Ag/Ag Cl-CN heterojuctions show highest photocatalytic activity,and the degradation efficiency of rhodamine B can reach 98.5% and reduction efficiency of hexavalent chromium is 39.5%.Furthermore,Ag/Ag Cl-CN nanorods still maintain high photocatalytic activity after four cycles of degradation Rh B,indicating that Ag/Ag Cl-CN heterojunction has good stability and cyclicity.