Preparation And Photocatalytic Properties Of G-C₃N₄ Based Ternary Composites

Photocatalytic technology has good application prospects in dealing with fossil energy consumption and ecological environmental protection.Graphite carbon nitride as a photocatalyst shows good performance in photocatalytic degradation of pollutants,photocatalytic hydrogen production,etc.However,g-C₃N₄ also has defects such as small specific surface area and low quantum yield,which limits its practical application.In order to improve the photocatalytic performance of g-C₃N₄,it is a very effective method to combine it with other semiconductor materials to form composite materials.In this paper,the g-C₃N₄ used as a matrix,which combined with zinc oxide（ZnO）,silver chloride（AgCl）,silver sulfide（Ag₂S）,and bismuth ferrite(BiFeO₃)to form a series of ternary composite materials.X-ray powder diffraction（XRD）,scanning electron microscope（SEM）,transmission electron microscope（TEM）,X-ray photoelectron spectroscopy（XPS）,fluorescence spectrum（PL）,ultraviolet-visible diffuse reflection spectrum（UV-Vis DRS）,photoelectric Chemical test（PEC）and N₂adsorption desorption（BET）characterize the prepared ternary composite material.The photocatalytic performances of the samples were evaluated by degrading RhodamineB（RhB）,Acid OrangeⅡ（AOⅡ）under visible light irradiation.The main research contents are as follows:（1）.The ternary composite material x-AgCl/g-C₃N₄/ZnO were synthesized by reflux stirring（x=4.3,8.3,12,15.3 wt%,x:mass percentage of AgCl）.XRD,SEM and TEM analysis impied that:the microscopic morphology of x-AgCl/g-C₃N₄/ZnO showed the irregular aggregation of nanoparticles and the intergranular pores.We can see materials have clear crystal stripe that indicate good crystallinity.XPS analysis further confirmed that Zn was+2 valence,Ag was+1 valence,Cl was-1 valence,C1s analysis shows that there are C-N bond and N=C-N bond.UV-vis DRS absorption spectrum analysis showed that with the increase of x-AgCl mass ratio,the absorption edge of x-AgCl/g-C₃N₄/ZnO gradually shifted red.After 230 min of visible light irradiation,the degradation rates of x-AgCl/g-C₃N₄/ZnO degraded rhodamine b（RhB）were exceeds90%.Based on the analysis results of PL,PEC,and BET,it can be seen that the x-AgCl/g-C₃N₄/ZnO composite has a lower photogenerated electron（e^-）-hole（h⁺）recombination rate and a larger specific surface area,making it photocatalytic degradation activity better.The effects of the preparation parameters,such as reflux stirring time and temperature,on the photocatalytic properties of the synthesized catalyst were investigated.Finally,the quenching experiment revealed that the main active free radical components involved in the photodegradation process of x-AgCl/g-C₃N₄/ZnO are（h⁺）and·O^2-,which explains the photocatalytic mechanism of the process（2）.The x-Ag₂S/g-C₃N₄（x=10,20,30,40 wt%,x:mass percentage of Ag₂S）nanoparticles were synthesized by ultrasonic deposition-precipitation.x-Ag₂S/g-C₃N₄/ZnO ternary composite catalyst synthesized by mechanical stirring.XRD,SEM and TEM analysis implied that:the microscopic morphology of x-Ag₂S/g-C₃N₄/ZnO showed that the nanoblocks of nanoparticles and the intergranular pores.In addition,clear lattice stripes were been observed,and the surface material has high crystallinity.XPS analysis further confirmed that Zn was+2 valence,Ag was+1 valence,Based on the analysis results of PL,PEC,it can be seen that the x-Ag₂S/g-C₃N₄/ZnO composite has a lower photogenerated electron（e^-）-hole（h⁺）recombination rate,that can improve its photocatalytic performance.As the percentage of x increased,the photocatalytic efficiency of visible light gradually increased.The degradation rates of 40 wt%Ag₂S/g-C₃N₄/ZnO degraded RhB solution was 98%.（3）.A high efficient bina composite catalytic material 20 wt%Ag₂S/BiFeO₃ was prepared.Subsequently,it is combined with g-C₃N₄ of different qualities to form x-g-C₃N₄/20 wt%Ag₂S/BiFeO₃（x=0.15,0.2,0.25,0.3g,x:mass of g-C₃N₄）photocatalyst.XRD and SEM analysis showed that as the mass of g-C₃N₄ increased,the intensity of the diffraction peak corresponding to g-C₃N₄ in the composite material gradually increased.The microscopic morphology of x-g-C₃N₄/20 wt%Ag₂S/BiFeO₃ showed that nanoblocks of nanoparticles and obvious slits.That can refract light more times to improve light utilization.In the photocatalytic performance test experiment,the degradation activity of the x-g-C₃N₄/20 wt%Ag₂S/BiFeO₃ composite for RhB first increased and decreased as the mass of g-C₃N₄ increased.The reason may related to the doping amount of g-C₃N₄,which causes the specific surface area of the material to increase first and then decrease.