Preparation Of Graphite Phase Carbon Nitride-based Composites And Photocatalytic Activities

Due to the rapid consumption of limited fossil fuels and the subsequent environmental pollution problems,it is highly anticipated to address these problem and develop a sustainable society.Among those,graphite-phase polymer carbon nitride?g-C₃N₄?as a kind of excellent semiconductor material has drawn many attentions all over the world.It has many advantages,such as good thermal stability and chemical stability,suitable band structure,simple and inexpensive preparation process and controllable energy band structure,thus widely used in the field of photo catalysis.In this thesis,the preparation of homogeneous g-C₃N₄-basedcomposite by dissolving g-C₃N₄ in concentrated sulfuric acid is reported.Two aspects are discussed in this paper about the process of preparing g-C₃N₄/sulfur-mediatedg-C₃N₄ composites.The result showed that the photocatalytic hydrogen production of g-C₃N₄ can be improved effectively by forming a composite.The details are listed as follows:1.g-C₃N₄ and sulfur-mediated g-C₃N₄ were synthesized by using dicyandiamide and thiocyanuric acid as precursors after calcinations at high temperature.The two compounds were dissolved in concentrated sulfuric acid at high temperature and then precipitated by using a poor solvent,and the precipitated sample was calcined for the 2nd time at high temperature.However,the photocatalytic hydrogen production test showed the photocatalytic performance of the composites was not improved.After X-ray diffraction,FT-IR,fluorescence and other analysis,it was showed that the failure of composite materials was because the true heterojunction between the two compounds were not effectively formed.2.On the basis of the above work,the experimental scheme was modified.After dissolving graphite carbon nitride with concentrated sulfuric acid,it was directly mixed with thiocyanuric acid to form a paste,instead of mixed with sulfur-mediated graphite carbon nitride,and then precipitated together and calcined at high temperature.The photocatalytic hydrogen production of the composites was 32.6 times higher than that of bulk carbon nitride,and 2.3 times higher than that of the composites by physical mixing.The results of X-ray diffraction,FT-IR,UV-vis and fluorescent spectra showed that the performance of the composite was improved by the formation of the effective heterojunctionin the composite materials.