Preparation of H4SiW12O40/Bi2WO6 nano-photocatalyst by supercritical hydrothermal synthesis and its photocatalysis denitrification performance
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摘要: 采用超临界水热合成方式极速合成一种H4SiW12O40/Bi2WO6光催化剂，通过X射线衍射（XRD）、场发射扫描电子显微镜（SEM）、透射电子显微镜（TEM）、比表面积及孔隙度（BET）测定对所合成催化剂的结构和性质进行了考察，并以吡啶含量为15 mg/g的模拟油对光催化剂的脱氮效果进行评价。结果表明，该光催化剂为二维纳米片自组装成的三维球状结构，其中，H4SiW12O40与Bi2WO6不是简单的固载关系而是在超临界水热条件下生成一种新的晶相，正是由于这种晶相的存在，使得H4SiW12O40牢固固载在Bi2WO6光催化剂本体上的同时，对光生载流子进行了有效疏导，提升了H4SiW12O40/Bi2WO6光催化剂的使用寿命和光催化活性。本研究针对光催化剂制备周期与晶形发育的矛盾，将超临界水热技术与光催化剂模板导向合成技术有机结合，在获得良好晶形异质结构H4SiW12O40/Bi2WO6光催化剂的同时明显缩短了光催化剂的制备周期，从而降低了催化剂的制备成本，攻克了光催化剂工业化应用的主要矛盾，所制备的H4SiW12O40/Bi2WO6光催化剂轻质油脱氮效率达97%以上。Abstract: An immobilized nano-photocatalyst H4SiW12O40/Bi2WO6 was quickly prepared by the supercritical hydrothermal synthesis method. The properties, morphology and structure of the prepared catalysts were investigated and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), and transmission electron microscope (TEM) and BET, respectively. The photocatalytic denitrification properties were evaluated by using the model oil with 15 mg/g pyridine. The results show that the photocatalyst is the self-assembly three-dimensional spherical structure by two-dimensional nano-flakes, and the relationship between Bi2WO6 and H4SiW12O40 is not a simple solid loading, but is a new crystal under the condition of supercritical water. It is because the existence of this kind of crystal that the H4SiW12O40 is firmly fixed on the Bi2WO6 photocatalyst and the photocatalytic activity and service life of H4SiW12O40/Bi2WO6 photocatalyst are improved. In view of the contradiction between the preparation period of photocatalyst and the crystal development, the supercritical hydrothermal technology and the photocatalyst template-oriented synthesis technology are organically combined to obtain the H4SiW12O40/Bi2WO6 photocatalyst with good crystal heterostructure and greatly shorten the preparation period of the photocatalyst, greatly reduce the preparation cost of the catalyst and overcome the main contradiction of the industrialized application of the photocatalyst. The nitrogen removal efficiency of the prepared H4SiW12O40/Bi2WO6 photocatalyst for light oil is as high as 97%.
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Key words:
- supercritical hydrothermal synthesis /
- H4SiW12O40 /
- Bi2WO6 /
- photocatalysis /
- denitrification
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图 1 采用超临界水热法制备的固载不同含量H4SiW12O40的H4SiW12O40/Bi2WO6光催化剂的XRD谱图
Figure 1 XRD patterns of H4SiW12O40/Bi2WO6 with different H4SiW12O40 loadings prepared by supercritical hydrothermal synthesis
w(H4SiW12O40): a: 10%; b: 15%; c: 20%; d: 25%; e: 30%
◆: Bi2WO6; ●: Bi2SiWO2
图 2 采用超临界水热法制备的H4SiW12O40固载量(w=20%)的H4SiW12O40/Bi2WO6光催化剂的扫描电镜照片
Figure 2 SEM images of H4SiW12O40/Bi2WO6 (H4SiW12O40 w=20%)prepared by supercritical hydrothermal synthesis
图 3 采用超临界水热法制备的H4SiW12O40固载量(w=20%)的H4SiW12O40/Bi2WO6光催化剂的透射电镜照片
Figure 3 TEM images of H4SiW12O40/Bi2WO6 (H4SiW12O40 w=20%) prepared by supercritical hydrothermal synthesis
图 4 不同方法制备的催化剂的紫外可见漫反射光谱谱图
Figure 4 UV-vis diffuse reflectance of catalysts
a: H4SiW12O40/Bi2WO6 (H4SiW12O40 w=20%)prepared by supercritical hydrothermal synthesis;
b: H4SiW12O40/Bi2WO6 (H4SiW12O40 w=20%) prepared by traditional liquid phase synthesiss; c: Bi2WO6
图 6 传统水热法(a)和超临界水热法(b)制备的催化剂的氮气吸附-脱附等温线
Figure 6 N2 adsorption-desorption isotherms for (a) the catalyst prepared by traditional liquid phase synthesis and (b) the catalyst prepared by supercritical hydrothermal synthesis
图 7 传统水热法(a)和超临界水热法(b)制备的催化剂的孔径分布
Figure 7 BJH pore size distribution curves of (a) the catalyst prepared by traditional liquid phase synthesis and (b) the catalyst prepared by supercritical hydrothermal synthesis
图 8 采用超临界水热制备条件下H4SiW12O40固载量对H4SiW12O40/Bi2WO6光催化剂脱氮性能的影响
Figure 8 Denitrification performance of H4SiW12O40/Bi2WO6 with different H4SiW12O40 loadings prepared by supercritical hydrothermal synthesis
图 9 不同方法制备的催化剂脱氮性能对比
Figure 9 Denitrification performance of catalystsprepared by different methods
: supercritical-H4SiW12O40/Bi2WO6; : traditional-H4SiW12O40/Bi2WO6; : Bi2WO6
表 1 传统水热法(a)和超临界水热法(b)制备的催化剂比表面积及平均孔径
Table 1 Specific surface area of the catalysts
Specific surface
area A/(m2·g-1)Average pore
size d/nma 24.87 4.89 b 30.15 3.92 
下载: 导出CSV
表 2 不同方法制备周期对比
Table 2 Preparation period of the catalyst
Traditional
phase
synthesisMicrowave-
assisted liquid
phase synthesisSupercritical
hydrothermal
synthesis12h 6h 10s
下载: 导出CSV
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