Preparation And Photocatalytic Performance Of G-C₃N₄ Based Composite Photocatalysts

Energy and environment are two major problems of nowadays society. Therefore, a kind of renewable energy and environmentally friendly technology is desirable. In recent years, photocatalysis technology, as a new technology, is applied to energy and environmental and it can effectively solve the severe problem. In the field of photocatalytic, TiO₂ has become the most widely used semiconductor material due to its unique advantages. However, its wide band gap （>3.2eV） results in not absorbing visible light of solar spectrum. So, in order to improve its photocatalytic activity, many methods was studied to modify TiO₂, such as ion doping, morphology modification and semiconductor compound. Moreover, developing the new visible-light-responsive photocatalysts is an effective way to solve this problem. g-C₃N₄ is a non-metallic semiconductor material, which can absorb visible light resulting the effective use of solar energy spectrum. But the traditional g-C₃N₄ has usually small specific surface area and low quantum efficiency, and thus the modification of g-C₃N₄ is required to effectively overcome the shortcomings. Therefore, in this paper two different g-C₃N₄-based composite catalysts were synthesized, and characterized. At the same time, their photocatalytic activity and reaction mechanism were investigated.1. Ag₃VO₄/g-C₃N₄ composite photocatalyst was prepared using a facile method and the structure and optical properties of samples were investigated in detail. In addition, the effect of Ag₃VO₄ amount in photocatalytic activity was also investigated. XRD, FT-IR and XPS were applied to investigate the structure of the catalyst. The results showed that loading of Ag₃VO₄ did not change the structure of g-C₃N₄. The result of UV-vis DRS showed that the absorption wavelength of Ag₃VO₄/g-C₃N₄ was obvious red shifted. Because of the forming of Ag₃VO₄/g-C₃N₄ composite photocatalyst, the recombination of the photogenerated carrier was obviously decreased.2. A series of Ag₂O/Ag/g-C₃N₄ NS visible-light responsive plasmonic heterojunction photocatalysts were prepared by a simple photodeposition method and the photocatalytic activities for the degradation of RhB was also investigated.TEM, AFM, XRD, XPS, FT-IR and UV-vis were applied to investigate the morphology, structure and optical properties of photocatalysts. The experimental results showed that the Ag（10.0）/g-C₃N₄ NS catalyst presents the best photocatalytic activity, which can degrade completely of 1.0×10-5 mol·L-1 RhB within 40 min. There is no significant decrease in photodegradation rate after five consecutive cycles, implying that the obtained Ag₂O/Ag/g-C₃N₄ NS heterojunction photocatalyst has high stability. Due to the surface plasmon resonance effect of Ag particles, the photocatalytic activity of Ag₂O/Ag/g-C₃N₄ NS heterojunction photocatalysts was obviously improved.