Composite Modification And Enhanced Photocatalytic Degradation Properties Of Graphite Phase Carbon Nitride （g-C₃N₄）

The graphite phase carbon nitride (g-C3N4) is receiving more and more attentions in the field of photocatalysis, as a novel semiconductor photocatalyst which can response to visible light effectively. However, there are also some disadvantages for g-C3N4 powder, such as narrow visible light response, small specific surface area, easy agglomeration and difficult recovery. In this paper, HNTs/g-C3N4, Fe2O3/g-C3N4 and g-C3N4/C nanofibers composite materials were synthesized to eliminate defects of g-C3N4 powder. These resulting materials were characterized by XRD, FTIR, TG, SEM, UV-VIS DRS, microscope, contact angle measurement and photocatalytic activity test, the relationship between the structure and the photocatalytic activities of these potocatalysts were also discussed. The main content and conclusions are summarized as follows:(1) The g-C3N4 powder was synthesized by the condensation method with urea, cyanamide, dicyandiamide, melamine as raw material. The product yield and photocatalytic activity of g-C3N4 powder synthesized with different raw materials were discussed. And then the effect of temperature on g-C3N4 crystal structure was also investigated. The results show that melamine is the most suitable raw material to synthesize g-C3N4, in comprehensive consideration of the product yield and photocatalytic activity. The sample calcined melane at 550℃ has the highest photocatalytic activity.(2) HNTs/g-C3N4 photocatalyst was synthesized by calcining the composite of melane and HNTs directly. The effects of different addition amount of HNTs on structure, morphology and photocatalytic activity of HNTs/g-C3N4 samples were investigated, and their stability was also evaluated. It is found that the HNTs/g-C3N4 samples can effectively broaden the scope of visible response, the 8% addition amount of HNTs can play the biggest role. The stability of HNTs/g-C3N4 samples is higher than that of g-C3N4 powder.(3) g-C3N4 nanosheets, signed as g-C3N4(S), were obtained by sintering of g-C3N4 powder and then ultrasonicating in liquid phase for some time.Fe (OH)3/g-C3N4(S) samples were synthesized through the reaction of ferric nitrate with ammonia upon g-C3N4 nanoheet layer followed by heat treatment. The results show that the sample doped with 5-8% Fe2O3 has higher photocatalytic activity than that of g-C3N4 powder.(4) g-C3N4(S)/PAN nanofibers were obtained by electrospinning. The impact of g-C3N4(S) addition on the electrospinning ability was discussed under the optimum electrospinning conditions. g-C3N4(S)/C nanofibers were obtained from g-C3N4(S)/PAN precursor through pre-oxidation and carbonization The results reveal that the photocatalytic activity and stability of g-C3N4(S)/C nanofibers were higher than that of g-C3N4 powder.