Studied On Preparation And Optical Properties Of G-C₃N₄ Modified Materials

Based on bulk g-C3N4 material,in order to overcome the shortcomings of bulk g-C3N4 material,the composite of bulk g-C3N4 and ZnO NRs was prepared with calcination and hydrothermal methods.In order to increase the specific surface area of the bulk g-C3N4,the morphology of g-C3N4 nanotubes(g-C3N4 NTs)were synthesized by hydrothermal and calcination methods.In order to improve the physical properties and modify the band structure of g-C3N4,Na doped g-C3N4 NTs were prepared via heat treatment method.The optical properties of g-C3N4 can be improved by these modification methods.The researches of this thesis include the following contents:1.The effect of ZnO NRs composite on the structure and photocatalytic properties of bulk g-C3N4:the XRD measurement results show that the intensity of the ZnO characteristic peak decreases first and then increases with the increase of the hydrothermal time,which is due to the gradual dissolution of ZnO seed particles and the growth of ZnO nanorods during the hydrothermal process.The photocatalytic properties of the samples were examined with the degradation of methyl orange(MO)solution at room temperature.The composite of g-C3N4/ZnO NRs greatly improves the photocatalytic properties of g-C3N4 by the separation of photo-generated electron-hole pairs.Furthermore,the morphology of ZnO nanorods regulated by hydrothermal time has a significant effect on their photocatalytic performance,and the composite with ZnO nanorods grown for 3 h shows the best photocatalytic performance.2.The supramolecular precursor of melamine and cyanuric acid was constructed by hydrothermal method.The effects of hydrothermal reaction temperature and time on the morphology and optical properties of g-C3N4 NTs were studied:according to the SEM measurements,with the increase of the hydrothermal reaction temperature of precursor,the formed g-C3N4 NTs are smooth and uniform,and the diameter becomes larger,and the specific surface area of the corresponding nanotubes decreases.Similarly,with the increase of hydrothermal reaction time of precursor,the formed g-C3N4 NTs are smooth and uniform.The specific surface area test results show that when the hydrothermal condition is at 150? for 20 h,the specific surface area of g-C3N4 NTs is the largest.The UV-Vis DRS and PL results show that the synthesis of nano-scale g-C3N4 NTs results in a blue shift of its absorption edge,and the formation of tubular structure slightly improves the absorption intensity.3.As the performance of the prepared g-C3N4 NTs is still low,the effect of Na doping on the structure and optical properties of g-C3N4 NTs was studied:Na doping changes the crystal quality of g-C3N4 NTs that the crystal quality first increases and then decreases with the increase of Na doping concentration.And according to the FTIR test results,Na doping introduces some defects in g-C3N4 NTs,which is conducive to the improvement of photocatalytic performance.In addition,the impurity energy level formed by Na doping increases the electron concentration,changes the energy band structure,results in a red shift of the intrinsic absorption edge of g-C3N4 NTs,and the recombination of photo-generated electron-hole pairs is inhibited,then the lifetime of carriers is prolonged.Therefore,the photocatalytic performance of Na doped g-C3N4 NTs is greatly improved.