Synthesis And Photocatalytic Performance Of Graphene-like Carbon Nitride-Based Modified Meterials

The energy crisis and water pollution are two critical problems to be solved in China,even the world.Photocatalysis technology,a new advanced oxidation technology,can utilize the internal photoelectric effect of the semiconductor to be used in the degradation reaction of macromolecular organic pollutants,by converting light energy into chemical energy.The g-C₃N₄ material,a non-metallic polymer semiconductor,has a unique band structure and good visible light response performance,which is highly concerned by researchers.In this paper,the research was carried out to investigate the effects of preparation conditions and modification methods on the photocatalytic properties of the samples.The characteristics of the prepared samples,just like crystal structure,morphology,surface area,were obtained by by XRD,SEM,FT-IR,XPS,UV-Vis DRS and other characterization methods.The photocatalytic performance of the samples were investigated by the degradation efficiency of Rhodamine B.The key contents of this study are as the following:Ⅰ.The bulk phase g-C₃N₄ were prepared by thermal polymerization with melamine as precursor.The effect of synthesis temperature on the performance of the sample was investigated.The optimum temperature was determined to be 600°C.Further,600B-g-C₃N₄ was subjected to delamination treatment,and samples of 600P1-g-C₃N₄ and 600P2-g-C₃N₄ were obtained by ultrasonic chemical peeling and thermal oxidative stripping.The results showed that 600P2-g-C₃N₄ exhibits a thin nanosheet structure with a large specific surface area（39.211 m²/g）,and increased utilization of light energy（2.76 eV）.The degradation efficiency of Rhodamine B was67.57%within 150 min.Ⅱ.The Bi₂WO₆/600P2-g-C₃N₄ composite samples were prepared by one-step hydrothermal method.The factors,such as the mass ratio,hydrothermal reaction time and pH values,were studied by experiments and characterization.It is found that,when the mass ratio of Bi₂WO₆and 600P2-g-C₃N₄ was 4/1,the hydrothermal time was 24 h,and the precursor pH was 1,the samples could be a fluffy layered intercalated structure.The maximum absorption wavelength was extended to 480 nm.Moreover,the reaction rate and stability of Bi₂WO₆/600P2-g-C₃N₄were improved.Ⅲ.The process parameters of the degradation reaction system under Bi₂WO₆/600P2-g-C₃N₄composite samples were studied.The results indicated that,adding 0.1 g catalyst to 100mL 20mg/L Rhodamine B solution,the degradation efficiency reached 90.90%。Ⅳ.Based on the Langmuir-Hinshelwood model,the reaction kinetics were studied for the reaction process.It was proved by the reactive group capture experiment that·O₂^-was the most active species in the reaction process.The photocatalytic degradation mechanism of Bi₂WO₆/600P2-g-C₃N₄ was also described.