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In this paper, a synthesis of the based on polycondensation precursor pyrolysis g-C3N4 powder . Using different precursors , the temperature programmed prepared g-C3N4; transition metal doped samples prepared Mg-C3N4 (M = Ag, Fe, Cu, Co, Ni) ; prepared by different methods Ag-g-C3N4 . X-ray diffraction ( XRD ) , UV - visible spectroscopy ( UV -vis ) , Fourier transform infrared spectroscopy ( FT - IR) , elemental analysis and transmission electron microscopy (TEM) and other means were used to characterize the structure and performance of the catalyst and the use of light degradation of methylene blue experimental evaluation of its photocatalytic properties . The detailed analysis of the different reaction conditions on the structure of the product , the degree of polycondensation , the photocatalytic activity . Determine the precursor , calcination temperature , metal -doped g-C3N4 sample photocatalytic properties investigated . The main research content and results are as follows : ( 1) pyrolysis polycondensation to organics precursor , cyanamide , dicyandiamide , melamine carbonitride precursor calcined at different temperatures under preparation class graphite structure carbon nitride (g-C3N4). Light catalytic experimental results show that , at 520 ℃ calcination two cyanide diamine system was the sample having a higher catalytic activity , methylene blue initial concentration of 50mg / L , after the the 5h visible light irradiation , methylene blue degradation rate can reach 66% ; (2) using the doping method of the transition metal modified g-C3N4 , Ag, Fe, Cu, Co, Ni - doped g-C3N4 preparing a metal-doped Mg - C3N4 Film - (M = Ag , Fe , Cu, Co, Ni), the experimental evaluation of catalyst reactivity degradation of methylene blue , the experimental results show that , Ag-g-C3N4 has the highest photocatalytic activity ; (3) Compare light deposition method, an impregnation method, doped Preparation Ag-g-C3N4 the photocatalytic activity of the sample , the photocatalytic activity of doped Preparation of Ag-g-C3N4 significantly superior to the other two methods , and the optimum doping amount of Ag was 0.1 wt % , and its catalytic properties best . Ag in atomic form into a g-C3N4 lattice with N atoms bonded to change the band structure of the g-C3N4 , thereby expanding its visible light absorption range , and is conducive to the photo-generated electron transmission .
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