Preparation Of G-C₃N₄ Heterojunction And Its Photocatalytic Performance Under Visible Light

At present, a new oxidation technology is widely used because it can react in a mild condition and it is also pollution-free. Besides, it can also degrades pollutants by utilizing solar power. However, with relatively broad forbidden bands, photo-catalysts used now can only provide a extremely low use factor, which greatly influences degradation efficiency of pollutants. Therefore, the research on how to improve the effect of photo-catalysis through modifying catalysts is imperative. In recent years, g-C3N4 has received extensive attention. Researchers began trying to improve the activity of photocatalysis by changing morphology, structure and performance through building heterojunction. The two main point will be discussed in this thesis are as follows:(1) Prepare g-C3N4 with melamine which was prepared by high temperature calcined, BiVO4 was prepared with ammonium metavanadate through hydrothermal. Then prepare g-C3N4/BiVO4 multiplex photo-catalyst with ultrasonic stirring method. It turns out that g-C3N4 and BiVO4 were distributed in different shapes. Fluorescence spectrum shows construction of heterojunction with large contact area can effectively promote the separation of photogenerated holes and electrons. g-C3N4/BiVO4 composite photocatalyst has excellent photocatalytice ability in the removation of RhB under the sunlight. The prominent enhancement is induced by the large contact area between C3N4 and mesoporus BiVO4 which can further restrain the recombination of photogenerated carriers. Under the irradiation of sunlight, the degradation efficiency is highest when the mass ratio of g-C3N4 and BiVO4 is 3:2.(2) Prepare g-C3N4/TiO2 photocatalyst with melamine and TiO2 through high-temperature calcination. It turns out that the TiO2 powders were distributed onto the surface of g-C3N4. After fluorescence spectrum analysis, the compound has the lowest intensity. It is because that there generates a electric field which promote the speed of the photongenerated. We degrade the target pollution RhB under the irradiation of visible light, we can find that because of the more photongenerated carriers join in the reaction with the recombination of g-C3N4 and TiO2, which greatly improves the degradation efficiency of the photocatalyst. the degradation efficiency is highest when the mass ratio of melamine and TiO2 is 4:1.