【作者】 王媛；

【导师】 陈胜利； 王爱军；

【作者基本信息】 中国石油大学(北京) ， 化学工程与技术， 2016， 硕士

【摘要】 半导体TiO₂作为一种重要的半导体光催化材料,由于其光催化活性高、化学稳定、安全无毒以及成本低廉等优点,在污染物的降解、太阳能电池和光化学合成等领域得到广泛的关注。但TiO₂作为光催化剂有两个缺点:其一是被光激发的电子和空缺容易复合,即量子产率低;其二是禁带宽度大造成的太阳光能量利用率低。为此,本论文创新性的提出双重带隙光子晶体光局域效应和纳米量子点效应协同提高TiO₂光催化性能的研究课题,研究内容与结果如下:首先利用化学浴沉积法（CBD）进行CdS量子点（QDs）敏化nc-TiO₂膜,以光催化降解乙醛为探针反应,研究膜催化剂在可见光下的光催化活性,结果表明:CdS QDs敏化明显提高nc-TiO₂膜的光催化性能,其乙醛反应动力学常数是nc-TiO₂膜的2.82倍。究其原因,一方面是因为CdS量子点的敏化使得nc-TiO₂的吸收向可见光区域延伸,从而提高了光催化活性。另一方面是因为CdS与TiO₂之间形成的异质结促进光生电子的转移,抑制光生电子-空穴再复合,从而提高了量子效率和光催化活性。其次,通过旋涂法在SiO₂ opal光子晶体上担载一层nc-TiO₂制备得到nc-TiO₂/SiO₂ opal光子晶体复合膜,以光催化降解乙醛为探针反应。结果表明:相对于nc-TiO₂/SiO₂-dis复合膜,TiO₂/SiO₂ opal光子晶体复合膜的光催化性能增强因子达到1.57,归因于当光子晶体的光子禁带（PBG）位置与nc-TiO₂膜吸收边吻合时,利用光子晶体的光局域效应提高nc-TiO₂膜紫外区域的光吸收利用率,进而提高光催化活性。再次,将SiO₂ opal光子晶体耦合到CdS QDs敏化nc-TiO₂膜制备CdS QDs敏化TiO₂/SiO₂ opal光子晶体复合膜,光子晶体的光子禁带设计在CdS QDs的电子带隙（即UV-Vis吸收边）,以光催化降解乙醛为探针反应。结果表明:CdS QDs/TiO₂/SiO₂ opal复合膜的光催化性能是单独nc-TiO₂膜的3.94倍。意味着利用光子晶体在光子禁带处反射效应和光局域效应可以提高CdS QDs敏化nc-TiO₂膜在可见光区域的光吸收利用率,从而增强nc-TiO₂膜的光催化活性。最后,利用垂直沉积法、室温漂浮法制备双重带隙光子晶体,将其与CdS QDs敏化nc-TiO₂膜复合制备复合型催化剂。并将SiO₂光子晶体的一个PBG频带设计在nc-TiO₂的UV-Vis吸收边处（³87 nm）,另一个PBG频带设计在CdS QDs的UV-Vis吸收边处（400⁵00 nm）。以光催化降解乙醛为探针反应,研究复合膜催化剂全光下光催化活性。结果表明:以CdS QDs/TiO₂/SiO₂-dis复合膜为参比,CdS QDs/TiO₂/SiO₂-380,CdS QDs/TiO₂/SiO₂-460的增强因子分别为1.27、1.75,CdS QDs/TiO₂/双带隙Si O2 opal复合膜增强因子达到2.07。究其原因,一方面光子晶体层的带隙频带与CdS QDs电子带隙的耦合作用提高了CdS QDs敏化nc-TiO₂在可见光区域的光吸收利用率;另一方面双带隙光子晶体和CdS QDs的协同效应进一步显著提高TiO₂的光催化性能。更多还原

【Abstract】 Titanium oxide（TiO₂）,as an important semiconductor photocatalytic material,has been attracting worldwide attention in environmental cleanup,solar cells and photolysis of water,owing to its good photocatalytic performance,high chemical stability,low toxicity,availability and low price,etc.However,TiO₂ as a photocatalytic material has two shortcomings: one is its quick recombination of ultraviole-light-excited electron-hole pairs,the other is the low light absorption rate caused its large electronic bandgap（EBG）.Therefore,in this paper,we put forward the research topic that TiO₂ activity enhancement through the synergistic effect of photons localization of photonic crystals（PCs）with double PBGs and the CdS quantum dots（QDs）effect,the research content and results are as follows:To begin with,CdS QDs sensitized TiO₂ membrane was synthesized through doping the TiO₂ membrane with CdS QDs by chemical bath deposition method（CBD）.The photodegradation of gaseous CH3CHO（acetaldehyde）was used as probe reaction to test the photocatalytic activity of the prepared membranes under visible light irradiation,and the results showed that the CdS QDs sensitization can enhance the photocatalytic activity of TiO₂ membrane,with the acetaldehyde degradation rate constant（k）on CdS QDs/TiO₂ membranes being 2.82 times of that on plain TiO₂ membranes.Firstly,CdS QDs extended the light absorption to the visible region,thus enhancing the photocatalytic activity.Secondly,the heterojunction between CdS and TiO₂ promoted the transfer of photo-generated electrons,which inhibited the recombination of photogenerated carriers,thus improving the quantum efficiency and photocatalytic activity.Secondly,TiO₂/SiO₂ opal composite membranes were fabcricated by spin-coating a layer of nc-TiO₂ onto the SiO₂ opal layer,and the photodegradation of acetaldehyde was used as probe reaction.The results showed that the enhancement factors for TiO₂/SiO₂-380 membranes was 1.57 compared with nc-TiO₂/SiO₂-dis,which benefited from the photons localization of PCs when the PBG of the SiO₂ PCs overlapping with the absorption edge of TiO₂.Once again CdS QDs/TiO₂/SiO₂ opal composite membrane was prepared by coupling SiO₂ opal layer onto the CdS QDs/TiO₂ membrane,and the PBG of the SiO₂ opal PCs layer was designed at the EBG of the CdS QDs.The photodegradation of gaseous CH3 CHO was used as probe reaction.The results showed that acetaldehyde degradation rate constant on CdS QDs/TiO₂/SiO₂ opal composite membrane reached four times of that on plain TiO₂ membrane.The light harvesting efficiency of CdS QDs sensitized TiO₂ membrane in the visible light region can be improved through the light reflection effect and photons localization at the PBG of photonic crystal,thus improving the photocatalytic activity.Finally,we prepared the PCs with double PBGs through room temperature floating self-assembly and the vertical deposition technique.Then coupling a photonic crystal with double-PBGs onto a CdS quantum dots sensitized TiO₂ layer to prepare a composite membrane.One of the PBGs was designed at the age of the EBG of TiO₂,and the another PBG designed at the age of the EBG of the CdS QDs.The gaseous CH3 CHO was used as probe reaction to evaluate the photocatalytic activity of the composite membranes under the while light irradiation.The results showed that enhancement factors for CdS QDs/TiO₂/SiO₂-380,CdS QDs/TiO₂/SiO₂-460 and CdS QDs/TiO₂/SiO₂ opals with double PBGs were 1.27,1.75 and 2.07 in comparison with the control of CdS QDs/TiO₂/SiO₂-dis.To find out its cause,on the one hand the coupling effect of the PBG of PC and the EBG of CdS QDs improved the light harvesting efficiency of CdS QDs/TiO₂ in the visible light region,on the other hand the synergistic effect of PCs with double PBGs and CdS QDs significantly improved the photocatalytic activity of TiO₂.更多还原