Modification Of Graphite-like Carbon Nitride Photocatalyst

Graphite-like carbon nitride is a new nonmetallic photocatalyst.It has good photoresponsiveness under visible light radiation and has a very good application prospect.However,its photocatalytic performance still cannot be used in mass production.At present,the research on graphite-like carbon nitride is mainly about how to improve the photocatalytic efficiency.The graphite-like carbon nitride prepared by common methods not only has a small specific surface area,but also has a low quantum efficiency due to the high recombination rate of photogenerated electrons and holes.In addition,its response range of visible light is relatively narrow,and it has the problem of insufficient absorption under sunlight irradiation.Modification of graphite-like carbon nitride can effectively change the electronic structure and morphological characteristics,thus broadening and adjusting its catalytic performance and application range.Among them,doping modification and composite modification are the main methods to modify graphite-like carbon nitride.In this paper,the photocatalytic properties of the modified graphite-like carbon nitride were studied through three methods of ytterbium metal doping modification,ytterbium metal and non-metallic phosphorus co-doping modification and carbon quantum dot composite modification.The photocatalytic properties of the highly active graphite-like carbon nitride prepared by the modified graphite-like carbon nitride were significantly improved.The specific contents of this paper are as follows:(1)With melamine and ytterbium chloride as raw material,the use of liquid in the Brownian motion to make melamine and ytterbium chloride heating miscibility,then under low pressure barometric treated precursor for drying,the samples in the tube furnace(nitrogen flow)further reaction,using liquid phase synthesis of the ytterbium doped method step ions doped graphite carbon nitride.After 30 minutes of xenon lamp irradiation,the degradation efficiency of rhodamine B increased from28.3% to 71.5%.By means of XRD,SEM,BET and PL spectroscopy,the reasons for the increase of photocatalytic activity were investigated.The characterization results showed that the photocatalytic efficiency of the graphitized carbon nitride doped byytterbium was improved by increasing the band gap width and effectively separating photogenerated electron-hole pairs.(2)Melamine,ytterbium chloride and phosphorus standard solution were used as raw materials.Metal ytterbium in section in the last chapter,on the basis of the optimal doping ratio,adding different amounts of phosphorus standard solution,using the same method as the section in the previous chapter step synthesized ytterbium metal,non-metallic phosphorus were doped graphite carbon nitride,the photocatalytic activity increased the concentration of the pollutants(rhodamine B)test and samples were doped with metal ytterbium doped best proportion of samples were compared.After 60 minutes of xenon lamp irradiation,the degradation rate of rhodamine B increased from 25.9% of ytterbium single doping to 54.1%.By means of XRD,XPS,SEM,BET and PL spectroscopy,it can be known that the co-doping of ytterbium and phosphorus affects the electronic structure of graphite-like carbon nitride,and also results in the effective separation of photogenerated electron-hole pairs,which further improves the photocatalytic activity.(3)A carbon quantum dot(CQDs)with different luminescence intensity and luminescence wavelength was selected,and the carbon quantum dot was used to construct a hetero junction with graphite-like carbon nitride.In this chapter,the photocatalytic activity of carbon quantum dots and graphite carbon nitride composites is discussed,and the effect of the luminescence intensity and wavelength of CQDs on the photocatalytic efficiency is preliminarily studied.After the photocatalytic activity test,the degradation efficiency of rhodamine B increased from 20.8% to 45.5% after80 minutes of light.Through the characterization of XRD,SEM,BET and PL spectra,it can be seen that the hetero structure formed by carbon quantum dots and graphite-like carbon nitride effectively inhibits the recombination of photogenerated electron-hole pairs and significantly improves the photocatalytic activity.