Preparation and photocatalytic properties of WO3-Ag/graphitic C3N4 Z-scheme composite photocatalyst
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摘要: 采用水热法合成WO3纳米棒，并通过简单的溶剂蒸发法及光沉积法实现WO3-Ag/石墨相C3N4(g-C3N4)复合光催化剂的合成。采用XRD、SEM、TEM等对材料进行全面表征。结果表明，由于成功构建了Z型异质结，WO3-Ag/g-C3N4复合光催化剂能够拓展可见光响应，有效抑制光生电子与空穴复合。最佳工艺条件下所得WO3-Ag/g-C3N4复合光催化剂在100 min时光催化降解罗丹明B (RhB)的效率可达96.8%，且WO3-Ag/g-C3N4复合光催化剂具有优异的稳定性。光催化机制表明，光催化实验中真正的活性物质为羟基自由基与超氧自由基。Abstract: WO3 nanorods were synthesized by hydrothermal method and WO3-Ag/graphitic C3N4 (g-C3N4) composite photocatalysts were synthesized by simple solvent evaporation and light deposition. The materials were characterized by XRD, SEM and TEM, et al. The results show that the WO3-Ag/g-C3N4 composite photocatalysts can expand the visible light response and effectively inhibit the photogenic electron and hole recombination due to the successful construction of Z-scheme heterojunction. Under the optimal conditions, the catalytic degradation efficiency of Rhodamine B (RhB) in 100 min is up to 96.8%, and the WO3-Ag/g-C3N4 composite photocatalysts have excellent stability. The photocatalytic mechanism indicates that the real active substances in photocatalytic experiments are hydroxyl radical and superoxide radical.
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Key words:
- C3N4 /
- WO3 /
- Ag /
- nanoparticles /
- composite /
- photocatalysts
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图 2 不同WO3质量分数的WO3/g-C3N4复合光催化剂的XRD图谱
Figure 2. XRD patterns of WO3/g-C3N4 composite photocatalysts with different mass fractions of WO3
图 3 不同Ag质量分数的WO3-Ag/g-C3N4复合光催剂的XRD图谱
Figure 3. XRD patterns of WO3-Ag/g-C3N4 composite photocatalysts with different mass fractions of Ag
图 4 不同水热时间的WO3的SEM图像
Figure 4. SEM images of WO3 with different hydrothermal times ((a)6 h; (b)8 h; (c)10 h; (d)12 h; (e)12 h)
图 5 WO3-Ag/g-C3N4复合光催化剂的TEM图像(a)和HRTEM图像(b)
Figure 5. TEM (a) and HRTEM (b) images of WO3-Ag/g-C3N4 composite photocatalysts
图 6 WO3、WO3/g-C3N4和WO3-Ag/g-C3N4复合光催化剂的UV-Vis漫反射图谱(a)和禁带宽度图谱(b)
Figure 6. UV-Vis diffuse reflectance spectra (a) and band gap spectra (b) of WO3, WO3/g-C3N4 and WO3-Ag/g-C3N4 composite photocatalysts
图 7 WO3/g-C3N4和WO3-Ag/g-C3N4复合光催化剂的荧光光谱
Figure 7. Fluorescence spectra of WO3/g-C3N4 and WO3-Ag/g-C3N4 composite photocatalysts
图 8 纯g-C3N4及WO3/g-C3N4复合光催化剂的N2脱附-吸附曲线
Figure 8. N2 desorption-adsorption curves of pure g-C3N4 and WO3/g-C3N4 composite photocatalyst
图 9 WO3-Ag/g-C3N4复合光催化剂的XPS图谱: (a) Survey; (b) C 1s; (c) N 1s; (d) O 1s; (e) W 4f; (f) Ag 3d
Figure 9. XPS spectra of WO3-Ag/g-C3N4 composite photocatalyst: (a) Survey; (b) C 1s; (c) N 1s; (d) O 1s; (e) W 4f; (f) Ag 3d
图 10 WO3/g-C3N4和WO3-Ag/g-C3N4复合光催化剂可见光降解RhB曲线((a), (b))及其反应动力学拟合((c), (d))
Figure 10. Visible light degradation curves ((a), (b)) and reaction kinetics fitting ((c), (d)) of RhB by WO3/g-C3N4 and WO3-Ag/g-C3N4 composite photocatalysts
图 11 WO3-Ag/g-C3N4复合光催化剂降解RhB溶液的UV-Vis漫反射图谱
Figure 11. UV-Vis diffuse reflectance spectra of WO3-Ag/g-C3N4 composite photocatalyst degradating RhB solution
图 12 WO3-Ag/g-C3N4复合光催化剂4次循环降解RhB染料的结果
Figure 12. Degradation results of RhB for four times with existence of WO3-Ag/g-C3N4 composite photocatalyst
图 13 WO3-Ag/g-C3N4复合光催化剂在循环光催化实验前后的XRD图谱
Figure 13. XRD patterns of WO3-Ag/g-C3N4 composite photocatalyst before and after cyclic photocatalytic experiment
图 14 WO3-Ag/g-C3N4复合光催化剂添加不同捕获剂的RhB降解曲线
Figure 14. RhB degradation curves of WO3-Ag/g-C3N4 composite photocatalyst with different trapping agents
图 15 WO3-Ag/g-C3N4复合光催化剂的光催化机制
Figure 15. Photocatalytic mechanism of WO3-Ag/g-C3N4 composite photocatalyst
VB—Valence band; CB—Conduction band
表 1 WO3/石墨相C3N4 (g-C3N4)和WO3-Ag/g-C3N4复合光催化剂成分配比
Table 1. Compositions of WO3/graphitic C3N4 (g-C3N4) and WO3-Ag/g-C3N4 composite photocatalysts
Sample WO3/wt% Ag/wt% 5WO3/g-C3N4 5 — 10WO3/g-C3N4 10 — 15WO3/g-C3N4 15 — 20WO3/g-C3N4 20 — 15WO3-Ag/g-C3N4 15 1 15WO3-2Ag/g-C3N4 15 2 15WO3-3Ag/g-C3N4 15 3 
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