Preparation And Photocatalytic Properties Of Graphitic Carbon Nitride

Currently, environmental pollution and energy shortage are becoming serious problems. Searching for renewable energy has become a research hotspot and has attracted great attention. Graphitic carbon nitride(g-C3N4) with a lot of advantages such as hydrothermal and chemical stability, visible light response, non-poisonous, cheap raw material and so on, has attracted great attention. However, as a photocatalyst, it still remains some problems, such as the high recombination rate of photogenerated electron-hole pairs, the relatively low quantum efficiency, and narrow absorptionj, leading to the low sunlight utilization efficiency. Meanwhile, the photocatalytic activity of g-C3N4 is low due to its small specific surface area and low quantum yield. In this thesis, we prepared new type g-C3N4 with high specific surface area and high catalytic activity by hydrothermal method. The photocatalytic behaviors of the as-prepared samples were investigated by XRD, FTIR, XPS, SEM, TEM, BET, DRS, TG and Rh.B degradation.The main research contents and results are as follows:(1) In order to investigate the mechanism of g-C3N4, we prepared g-C3N4 through polycondensation method and use melamine, urea and thiourea as precursors. The experimental results show that the product yield of the g-C3N4 who was prepared by melamine was the highest, and the g-C3N4 with the highest efficiency was prepared by urea.(2) g-C3N4 derivatives was treated by hydrothermal method. Photocatalytic degradation results show that the CN-6 presents the highest photodegration activity. To study the mechanism of the g-C3N4 derivatives, we added capture agent in photocatalytic degradation experiment. Results show that the photocavity plays a main role in the process of photodegration, meanwhile ·O2-and ·OH play a supporting role.(3) High-efficiency g-C3N4 sample was prepared by calcination method use g-C3N4 derivatives as precursor. Photocatalytic degradation results show that the CN-6-500 presents the highest photodegration activity. To study the mechanism of high-efficiency g-C3N4, we added capture agent in photocatalytic degradation experiment. Results show that the ·O2- and ·OH play a main role in the process of photodegration, meanwhile photocavity plays a supporting role.Finally, the CN-6-500 sample exhibits higher photocatalytic activity, indicating that both hydro-thermal treatment and recalcination process are necessary for modifying the g-C3N4 photocatalytic property.