Photocatalytic performance of ZIF-8/g-C3N4 composite for deep oxidation of NO
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摘要: 采用热聚合法和原位沉积法分别制备g-C3N4、ZIF-8及不同质量比的ZIF-8/g-C3N4复合光催化材料,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)等表征手段对其结构性质进行表征。表征结果表明,合成的ZIF-8/g-C3N4复合材料没有破坏ZIF-8与g-C3N4原始的晶体结构与形貌,且ZIF-8与g-C3N4形成了异质结,ZIF-8/g-C3N4复合材料的BET比表面积比g-C3N4提高了30多倍。光催化氧化去除NO结果表明,12.5%-ZIF-8/g-C3N4的NO氧化去除效率最佳,且不生成有毒中间产物NO2,具有最优异的光催化活性,对于NO的氧化去除率可达55.1%。机理研究表明,基于g-C3N4的异质结构不仅抑制了光生载流子的复合,而且由于g-C3N4与ZIF-8之间的协同作用,促进了可见光的吸收以及反应物分子NO的吸附,从而提高了复合材料对NO的光催化氧化性能。Abstract: g-C3N4, ZIF-8 and ZIF-8/g-C3N4 composite photocatalysts with different mass ratios were prepared by thermal polymerization method and in-situ deposition method, respectively. The structural properties of prepared samples were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS), etc. The results showed that the ZIF-8/g-C3N4 composite did not destroy the original crystal structure and morphology of ZIF-8 and g-C3N4, and ZIF-8 formed a heterojunction with g-C3N4. The BET specific surface area of ZIF-8/g-C3N4 was improved more than 30 times compared with g-C3N4. The results of photocatalytic oxidation of NO showed that 12.5%-ZIF-8/g-C3N4 exhibited the best removal efficiency of NO and no toxic intermediate NO2 production, and it had the most excellent photocatalytic activity with the nitric oxide removal efficiency of 55.1%. The mechanism study showed that the formed heterostructure not only inhibited the recombination of photogenerated charge carriers, but also promoted the absorption of visible light and the adsorption of reactant molecular NO due to the synergy between ZIF-8 and g-C3N4, thus improving the photocatalytic oxidation performance of NO.
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Key words:
- photocatalysis /
- MOFs /
- composite photocatalyst /
- NO
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图 5 g-C3N4和ZIF-8/g-C3N4的光催化活性:NO去除率((a),(c));NO2的生成量(b);ZIF-8/g-C3N4光催化去除NO的循环活性图(d)
Figure 5 ((a), (c)) Photocatalytic performance of different photocatalyst samples for removal of NO under visible light irradiation; (b) Corresponding amount of NO2 generated over different photocatalyst samples; (d) Cyclic experiment of ZIF-8/g-C3N4 photocatalytic removal of NO
图 6 g-C3N4((a), (e))、ZIF-8((b), (f))、12.5%-ZIF-8/g-C3N4((c), (g))和PM-12.5%-ZIF-8/g-C3N4((d), (h))的SEM图像((a)−(d))与TEM图像((e)−(h))和12.5%-ZIF-8/g-C3N4的EDS元素分布图((i)−(l))
Figure 6 SEM ((a)−(d)) and TEM ((e)−(h)) images of g-C3N4((a), (e)), ZIF-8((b), (f)), 12.5%-ZIF-8/g-C3N4((c), (g)) and PM-12.5%-ZIF-8/g-C3N4((d), (h)); Elements mappings ((i)−(l)) of 12.5%-ZIF-8/g-C3N4
表 1 制备ZIF-8/g-C3N4纳米复合材料的原料配比
Table 1 Raw material ratio for preparing ZIF-8/g-C3N4 nanocomposite
Zinc acetate 2-methylimidazole Name 0.5 mmol 2 mmol 6.25%-ZIF-8/g-C3N4 1 mmol 4 mmol 12.5%-ZIF-8/g-C3N4 2 mmol 8 mmol 25%-ZIF-8/g-C3N4 3 mmol 12 mmol 37.5%-ZIF-8/g-C3N4 4 mmol 16 mmol 50%-ZIF-8/g-C3N4 表 2 ZIF-8-g-C3N4和12.5%-ZIF-8/g-C3N4纳米复合材料的比表面积、孔体积和孔径
Table 2 Specific surface areas, pore volumes and pore sizes of g-C3N4, ZIF-8 and 12.5%-g-C3N4/ZIF-8
Sample BET specific surface area
/(m2·g−1)Pore volume
/(cm3·g−1)Pore size
/nmZIF-8 1244.20 0.0573 2.301 g-C3N4 8.07 0.0479 28.8231 ZIF-8/g-C3N4 260.25 0.0488 2.7986 -
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