Preparation of graphitic carbon nitride with nitrogen-defects and its photocatalytic performance in the degradation of organic pollutants under visible light
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摘要: 通过在三聚氰胺热分解过程中加入NaHCO3制备出具有氮缺陷的石墨相氮化碳（g-C3N4），利用X射线衍射（XRD）、傅里叶变换红外光谱（FT-IR）、N2吸附-脱附、X射线光电子能谱（XPS）、紫外-可见漫反射光谱（UV-vis DRS）和固体荧光光谱（PL）等方法对其进行表征，并在可见光（λ > 420nm）照射下，以水相中罗丹明B（RhB）的降解为模型反应，研究了该氮缺陷g-C3N4对有机污染物降解的光催化活性。结果表明，引入氮缺陷可以提高g-C3N4对可见光的吸收以及电子-空穴对的分离效率，进而提高g-C3N4的可见光催化活性。催化剂CNK0.005、CNK0.01和CNK0.05在30min内对RhB的降解率分别为79.8%、100.0%和87.6%；而在相同条件下，没有氮缺陷的g-C3N4对RhB的降解率仅为59.8%。Abstract: Various graphitic carbon nitride (g-C3N4) materials having nitrogen defects were synthesized by adding NaHCO3 during the thermal polymerization of melamine. The as-prepared g-C3N4 samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), nitrogen adsorption-desorption, X-ray photoelectron spectroscopy (XPS), UV-visual diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence spectroscopy (PL); their photocatalytic activity in the degradation of Rhodamine B (RhB) under visible light irradiation was investigated. The results demonstrated that the unique nitrogen defects in g-C3N4 play an important role in broadening the absorption of visible light and enhancing the separation of electron-hole pairs. The photocatalytic activity of g-C3N4 with nitrogen defects is enhanced greatly; the RhB removal rates over the CNK0.005, CNK0.01, and CNK0.05 photocatalysts in 30 min reach 79.8%, 100.0% and 87.6%, respectively. In contrast, the pristine g-C3N4 free of nitrogen defects only gives an RhB degration rate of 59.8% under the same reaction conditions.
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Key words:
- g-C3N4 /
- nitrogen defects /
- visible light /
- organic pollutants /
- degradation
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Figure 1 Schematic procedures for the synthesis of g-C3N4 materials with nitrogen defects
Figure 5 Nitrogen adsorption-desorption isotherms and BJH pore size distribution of CNK0.01 and pristine g-C3N4
Figure 6 (a) UV-vis diffusive reflectance spectra of various g-C3N4 samples; (b) energy gap calculated by plotting (αhv)1/2 versus photon energy (Eg)
Figure 10 Kinetic curves for the RhB degradation over v arious g-C3N4 catalysts (linear correlation of ln(C/C0)vs.t)
Figure 12 Degradation of RhB over CNK0.01 in the presence of different radical scavengers
Table 1 First-order reaction kinetic parameters of various g-C3N4 samples
Sample Pristine g-C3N4 CNK0.005 CNK0.01 CNK0.05 k/min-1 0.029 0.055 0.145 0.076 R2 0.994 0.994 0.967 0.982 
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