Application of photocatalytic degradation of formaldehyde by g-C3N4-Ag/SiO2 heterostructure composites
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摘要: 将Ag、薄层石墨相氮化碳(g-C3N4)和硅铝胶球(SiO2)通过液相超声剥离-光化学沉积法-浸渍法合成复合光催化材料。设计甲醛降解密闭实验舱，探究g-C3N4、Ag-g-C3N4和g-C3N4-Ag/SiO2材料的光催化特性及其对甲醛的降解效果。结果表明，在可见光源条件下，对于g-C3N4-Ag/SiO2材料，降解甲醛的效率最高可达到65.6%。40%的相对湿度可有效提升降解效果。负载30 mg 4%Ag/g-C3N4的硅铝胶球循环使用16次时，甲醛降解效率仅下降9.71%。结合材料表征结果表明，通过超声剥离和Ag的引入，提升了材料可见光的吸收强度和吸收范围，并且有效促进了光生电子和空穴的分离，有效提升甲醛分子的降解效率。研究结果表明g-C3N4-Ag/SiO2材料具有优异的稳定性和良好的光催化性能，为实际有机污染物治理的应用提供了较好的科学基础。Abstract: Composite photocatalytic materials were synthesized by liquid-phase ultrasonic exfoliation-photochemical deposition method-impregnation method of monolithic Ag, thin layer of graphitic phase carbon nitride (g-C3N4) and silica-alumina colloidal spheres (SiO2). A formaldehyde degradation hermetic chamber was designed to investigate the photocatalytic properties of g-C3N4, Ag-g-C3N4 and g-C3N4-Ag/SiO2 materials and their degradation effects on formaldehyde. The results show that the efficiency of degradation of formaldehyde can reach up to 65.6% for SAG materials under visible light source conditions. 40% relative humidity can effectively enhance the degradation efficiency.The formaldehyde degradation efficiency decreases by only 9.71% when the silica-alumina spheres load with 30 mg 4%Ag/g-C3N4 are recycled for 16 times. The results of material characterization show that the visible light absorption intensity and absorption range of the material are enhanced by ultrasonic stripping and the introduction of Ag, and the separation of photogenerated electrons and holes are effectively promoted, which effectively enhance the degradation efficiency of formaldehyde molecules. The results show that the g-C3N4-Ag/SiO2 material has excellent stability and good photocatalytic performance, which provides a better scientific basis for the application of practical organic pollutant treatment.
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Key words:
- silica-alumina colloidal spheres /
- Ag /
- photocatalysis /
- graphitic phase carbon nitride /
- formaldehyde /
- degradation
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图 1 甲醛降解实验舱
Figure 1. Formaldehyde degradation chamber
1—Light source; 2, 7—Extraction sampling port; 3—Temperature and humidity meter; 4—Photocatalyst to be measured; 5—Formaldehyde volatile device; 6-Fan
图 2 块状石墨相氮化碳(g-C3N4)、g-C3N4-F、4%Ag-g-C3N4-F样品的XRD图谱
Figure 2. XRD patterns of bulk graphite phase carbon nitride (g-C3N4-B), g-C3N4-F and 4%Ag-g-C3N4-F
图 3 g-C3N4-B (a)、g-C3N4-F (b)、4%Ag-g-C3N4-F ((c)、(d)) 材料的SEM图像及4%Ag/g-C3N4-F ((e)、(f))的TEM图像
Figure 3. SEM images of g-C3N4-B (a), g-C3N4-F (b), 4%Ag-g-C3N4-F ((c), (d)) and TEM images of 4%Ag-g-C3N4-F ((e), (f))
图 4 SiO2 (a)和g-C3N4-Ag/SiO2-30 (b) 的SEM图像
Figure 4. SEM images of SiO2 (a) and g-C3N4-Ag/SiO2-30 (b)
图 5 g-C3N4-B、g-C3N4-F、4%Ag-g-C3N4-F紫外可见吸收光谱 (a) 及对应的Tauc曲线 (b)
Figure 5. UV-vis DRS (a) and corresponding Tauc’s plot (b) of g-C3N4-B, g-C3N4-F and 4%Ag-g-C3N4-F
图 6 g-C3N4-B、g-C3N4-F、4%Ag-g-C3N4-F的荧光图谱
Figure 6. Photoluminescence spectra of g-C3N4-B,g-C3N4-F and 4%Ag-g-C3N4-F
图 7 g-C3N4-B、g-C3N4-F、4%Ag-g-C3N4-F的瞬态光电流响应曲线 (a) 和电化学阻抗曲线 (b)
Figure 7. Transient photocurrent response curves (a) and EIS curves (b) of g-C3N4-B, g-C3N4-F and 4%Ag-g-C3N4-F
图 9 不同g-C3N4-Ag/SiO2样品降解甲醛的效果
Figure 9. Degradation efficiency of g-C3N4-Ag/SiO2 samples to formaldehyde
图 10 相对湿度对g-C3N4-Ag/SiO2-30降解甲醛效果的影响
Figure 10. Effect of relative humidity on formaldehyde degradation rate by g-C3N4-Ag/SiO2-30
图 11 g-C3N4-Ag/SiO2-30降解甲醛的循环稳定性实验
Figure 11. Cyclic stability experiment of g-C3N4-Ag/SiO2-30 for degradation of formaldehyde
图 12 g-C3N4-Ag/SiO2光催化降解机制
Figure 12. g-C3N4-Ag/SiO2 photocatalytic degradation mechanism
表 1 Ag-薄层石墨相氮化碳(g-C3N4-F)复合材料的命名
Table 1. Naming of Ag-thin layer graphite phase carbon nitride (g-C3N4-F) composites
Sample g-C3N4-F/mg Concentration of AgNO3/(mg·mL−1) AgNO3/mL Na2S/mL 0 500 0 5 2 1%Ag-g-C3N4-F 500 1 5 2 2%Ag-g-C3N4-F 500 2 5 2 4%Ag-g-C3N4-F 500 4 5 2 8%Ag-g-C3N4-F 500 8 5 2 12%Ag-g-C3N4-F 500 12 5 2 16%Ag-g-C3N4-F 500 16 5 2 
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表 2 石墨相氮化碳(g-C3N4)-Ag/SiO2复合材料的命名
Table 2. Naming of graphite phase carbon nitride (g-C3N4)-Ag/SiO2 composites
Sample Ag-g-C3N4-F/mg SiO2/g Ethyl alcohol/mL g-C3N4-Ag/SiO2-10 10 30 100 g-C3N4-Ag/SiO2-20 20 30 100 g-C3N4-Ag/SiO2-30 30 30 100 g-C3N4-Ag/SiO2-40 40 30 100 g-C3N4-Ag/SiO2-50 50 30 100
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