Flower Spherical BiOI Photocatalyst Prepared by Nanosheets
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摘要: 以硝酸铋和碘化钾为原料，水和乙二醇单甲醚的混合液为溶剂，通过水-溶剂热反应制备BiOI可见光光催化剂。采用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、紫外-可见-漫反射吸收光谱（UV-Vis-DRS）和Brunauer-Emmett-Teller（BET）等方法对样品进行了测试和表征。以甲基橙作为模型污染物，测试了BiOI在可见光下的光催化活性，并探讨了其在可见光下的光催化机理。结果表明：乙二醇单甲醚在混合溶剂中的比例对于BiOI光催化剂的形貌和性能有显著影响，乙二醇单甲醚的体积分数为50%时降解效果最佳，降解率达到77.9%，约为纳米片状BiOI光催化剂的14倍。Abstract: BiOI is considered as one of the most promising visible light photocatalysts because of its narrow band gap and layered structure. BiOI photocatalyst was synthesized by hydro-solvo-thermal process using bismuth nitrate and potassium iodide as the raw materials, and a mixed solution of water and 2-methoxyethanol was used as the solvent. The crystal structure, micro-morphology, light absorption performance and specific surface area of the samples were characterized by XRD, SEM, UV-Vis-DRS and BET, respectively. The photocatalytic activities of BiOI samples under visible-light irradiation were evaluated by the degradation of methyl orange. The results showed that the volume ratio of 2-methoxyethanol in the mixture solvent had a significant influence on the morphology and performance of the BiOI. The morphology of the BiOI photocatalyst prepared at 50% volume ratio of 2-methoxyethanol in the mixture solvent was a flower microsphere. The BiOI microspheres were fabricated by nanosheets with the characteristics of mesoporous structure. Because of the addition of 2-methoxyethanol, the crystal growth of BiOI was strongly restrained, and the dominant growth along (110) plane was very obvious. The photocatalytic activity of BiOI had been significantly improved because of the larger specific surface area and the flower spherical structure. After 150 min of visible light irradiation, 77.9% methyl orange were degraded, and the degradation rate was 14 times that of the nanosheet BiOI photocatalyst. The photocatalytic mechanism of BiOI under visible light was proposed. The photoinduced holes(h+) and ∙O2− are the active species in the process of photocatalytic degradation of MO. Furthermore, the photo-generated holes (h+) were the most important photocatalytic active species.
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Key words:
- BiOI /
- photocatalyst /
- hydro-solvo-thermal procedure /
- 2-methoxyethanol /
- flower spherical /
- photocatalytic mechanism
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图 1 不同溶剂体积比下制备的BiOI样品的XRD谱图
Figure 1. XRD pattern of BiOI samples prepared under different solvent volume ratios
图 2 不同溶剂体积比下合成的BiOI的SEM图
Figure 2. SEM image of BiOI synthesized under different solvent volume ratios
图 3 BiOI样品的氮气吸附-脱附等温线及孔径分布曲线(插图)
Figure 3. Nitrogen adsorption-desorption isotherms and the corresponding pore size distribution curve (inset) of BiOI samples
图 4 BiOI样品的紫外-可见-漫反射吸收光谱(a)；(αhν)1/2和hν的关系图(b)
Figure 4. UV-Vis-DRS of BiOI samples (a)；Plots of (αhν)1/2 vs hν of BiOI samples (b)
图 5 甲基橙的光催化降解曲线(a)；一阶动力学拟合图(b)
Figure 5. Photocatalytic degradation curve of MO (a); Fitting plots of pseudo-first-order kinetics (b)
图 6 捕捉剂对BiOI-50光降解MO过程的影响
Figure 6. Effect of scavenger on the photodegradation process of MO by BiOI-50
表 1 溶剂体积比对BiOI样品晶相结构的影响
Table 1. Effects of solvent volume ratio on the crystallite structure of BiOI samples
Sample L /nm I(102)∶I(110) BiOI-0 80.9 2.78 BiOI-25 27.9 0.99 BiOI-50 26.2 0.81 BiOI-75 18.2 1.03 
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表 2 溶剂体积比对BiOI样品比表面积、禁带宽度和反应速率常数 (k) 的影响
Table 2. Effects of solvent volume ratios on the specific surface area, band gap and reaction rate constant (k) of BiOI samples
Sample SBET/(m2·g−1) Eg/eV k/(10−3·min−1) BiOI-0 1.96 1.63 0.56 BiOI-25 23.14 1.66 4.64 BiOI-50 37.36 1.75 7.83 BiOI-75 33.76 1.67 5.41
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