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半导体光催化技术已经引起了很大的关注[1-3],尤其是卤化氧铋因其独特的性质,在污水处理、分解水、太阳能用于二氧化碳转化等领域得到了广泛的应用[4–6]。卤化氧铋的特点是[Bi2O2]2+层与2个卤素原子层通过静电作用交错形成,这种特殊的层状结构有利于光生电子空穴对的分离,从而在光催化过程中表现出良好的光催化性能[7-8]。同时,它们的性能还受其形状、尺寸、物相和暴露的晶面等因素的影响。例如,Contreras等制备了(110)和(001)晶面择优生长的碘化氧铋,显示出对环己醇有更高的选择性,环己醇的产率和峰强度(110)/(001)的比值之间具有线性依赖关系[9]。Liu等在生物质溶剂CMC-Na的辅助下合成了(010)晶面择优生长的2D纳米片组装成的3D BiOX,其对盐酸四环素的光催化活性高于(001)晶面择优生长的2D纳米片组装成的BiOX[10]。Aleksandra等采用溶剂热法在甘油中制备了BiOX半导体,这种方法可以影响BiOX的形貌、表面性质和光催化活性,系统的研究了不同离子作为卤素源和模板合成的BiOX的光催化活性[11]。Zhao等通过醋酸辅助水解获得了具有高效可见光催化活性的三维玫瑰状BiOBrxI1-x光催化剂,结果表明BET比表面积越大,3D玫瑰状形貌良好和(110)晶面择优生长对BiOBr0.8I0.2降解双酚A、罗丹明B和甲基橙有积极影响[12]。Mi等通过简单的一步水解法合成了带状分级结构的Bi4O5Br2,可见光照射下,(010)晶面高度暴露的带状Bi4O5Br2在降解水杨酸和间二苯酚方面比(101)晶面高度暴露的片状Bi4O5Br2表现出更高的光催化活性[13]。因此,对光催化剂的形貌、物相和暴露的晶面进行调控是非常重要的。
与BiOX相比,具有不同化学计量比的卤化氧铋,如Bi5O7I[14]、Bi24O31Br10[15]、Bi4O5Br2[16]和Bi12O17Cl2[17]等材料在光催化领域得到了广泛的研究。为了充分利用太阳能,有必要探索具有较高可见光吸收效率和光诱导电荷分离能力的光催化材料。在这一系列材料中,黄色的Bi12O17Cl2在降解污染物和去除NO方面表现出优异的可见光光催化活性[18–21]。Du等在不同的表面活性剂的条件下,通过简单的水热法成功合成了沿[200]方向择优生长的Bi12O17Cl2纳米片,它在光降解RhB和2-氯苯酚方面表现出比其他样品优越的光催化性能[22]。Xia等得到了Bi12O17Cl2超细纳米管,外层的管壁通过结构畸变产生表面氧缺陷,从而加速载流子迁移和促进CO2活化,其选择性催化CO转化效率是块状Bi12O17Cl2的16.8倍,即使在试验12 h后仍保持很好的稳定性[23]。Chang等在不同的煅烧温度下制备了一系列富氧Bi12O17Cl2样品,结果表明煅烧温度会极大的影响样品的微观结构和能带结构,进而影响对RhB的声催化降解效率[24]。因此,半导体的形貌和特殊结构是影响其光催化活性的重要因素。
本项工作中,通过简单的溶液法,在70 oC条件下合成了纳米片组装成的Bi12O17Cl2微米花。乙二醇在成功制备沿着[200]方向择优生长的Bi12O17Cl2过程中发挥了关键作用。与没有择优取向的Bi12O17Cl2纳米片相比,具有择优取向的Bi12O17Cl2纳米片对罗丹明B和亚甲基蓝的降解表现出优越的可见光催化活性,结果显示样品的形貌和暴露的晶面对其性能影响很大。通过捕获实验发现˙O2–和h+在光催化降解有机污染物过程中起主导作用。
乙二醇诱导Bi12O17Cl2晶面择优生长的合成及其光催化性能
Ethylene glycol induced synthesis of Bi12O17Cl2 crystals with preferred orientation and their photocatalytic study
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摘要: 通过液相沉淀法,利用乙二醇(EG)诱导成功地制备了沿[200]方向择优生长的Bi12O17Cl2微米花。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)、紫外-可见漫反射光谱(UV-vis DRS)和荧光光谱仪(PL)研究了所制备的光催化剂的相结构、形貌和光学性质。在可见光(350 W氙灯,λ>420 nm)照射下,考察了Bi12O17Cl2样品对罗丹明B(RhB)、亚甲基蓝(MB)的光催化降解性能。结果表明,沿着[200]方向择优生长的Bi12O17Cl2具有更优异的光催化活性,见光300 min后,对RhB的降解效率为77.56%,主要是由于它特殊的形貌和结构提高了光生电荷分离效率,同时,通过捕获实验研究了Bi12O17Cl2的光降解机理。
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关键词:
- 乙二醇 /
- Bi12O17Cl2微米花 /
- 择优生长 /
- 光催化
Abstract: Bi12O17Cl2 microflowers with preferentially oriented growth along [200] were successfully prepared by ethylene glycol (EG) induced through a liquid phase precipitation method. Powder X–ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM), X–ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence spectrometer (PL) were employed to study the phase structures, morphologies and optical properties of the fabricated photocatalysts. The photocatalytic degradation performance of Bi12O17Cl2 samples on rhodamine B (RhB), methylene blue (MB) were evaluated under visible light irradiation (350 W Xe lamp, λ>420 nm). The results showed that Bi12O17Cl2 sample grown along the [200] direction has better photocatalytic activity. After 300 min of light exposure, the degradation efficiency of RhB is 77.56%. Due to its special morphology and structure, which improves the efficiency of photogenerated charge separation. Trapping experiments were performed to reveal the photodegradation mechanism of dyes over Bi12O17Cl2 samples.-
Key words:
- ethylene glycol /
- Bi12O17Cl2 microflowers /
- preferred orientation /
- photocatalysis
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图 1 不同量的乙二醇制备的样品SEM图和XRD谱图(a) S1 (0 mL), (b) S2 (10 mL), (c) S3 (15 mL), (d) S4 (20 mL),(e) S5 (25 mL), (f) 相应的XRD 谱图
Figure 1. SEM images of five samples with different volumes of ethylene glycol (a) S1 (0 mL), (b) S2 (10 mL), (c) S3 (15 mL), (d) S4 (20 mL), (e) S5 (25 mL), (f) Corresponding XRD patterns of the five samples
表 1 样品的比表面积,孔体积和孔径。
Table 1. BET surface areas, pore volume, and pore size of the samples.
样品
Samples表面积/(m2·g−1)
Surface area孔体积(×10−2)/(cm3·g−1)
Pore volume孔径/nm
Pore sizeS3 30.3566 7.5729 9.9786 S5 24.4243 4.8968 8.0196 -
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