【作者】 赵阳；

【导师】 谭欣；

【作者基本信息】 天津大学 ， 化学工程， 2016， 博士

【摘要】 高性能光催化材料的开发一直是光催化技术发展的核心问题。而现有的光催化材料普遍存在太阳能利用率低和量子效率低两大问题,成为光催化技术发展的瓶颈。在光催化新材料中,BiOX（X=Cl,Br,I）以其特有的晶体结构和电子结构、优良的可见光吸收能力、较高的稳定性和低毒性成为研究的热点之一。本文选择BiOBr为研究对象,通过形貌控制、晶面调控和构造异质结,旨在进一步提高BiOBr的光催化活性和拓宽其应用范围,取得的原创性成果归纳如下:（1）采用溶剂热法,在体系中加入阴离子表面活性剂十二烷基硫酸钠（SDS）,在较低的反应温度下得到了BiOBr三维球形层状结构,这是阴离子表面活性剂在BiOX合成中的首次使用。SEM和TEM表明,SDS的加入使构成三维结构的二维纳米片厚度由160 nm降至约25 nm,而且构成纳米片的晶粒粒径有所减小。XPS结果显示,添加SDS后所得产物的表面氧缺陷有所增加。可见光下（λ≥420nm）降解RhB的测试表明,添加SDS所得的产物光催化活性更高,这归因于更多的表面氧缺陷为染料的吸附和降解提供了更多的活性位。（2）在上一个工作的基础上,通过调节前驱物Bi（NO₃）₃·5H₂O和KBr的浓度,得到BiOBr三维花形结构,该花形结构由部分暴露{111}晶面的二维纳米片自组装而成。这是关于BiOX{111}晶面的首次研究报道。SDS在{111}晶面的暴露中起到了重要作用。与BiOX自然暴露的{001}晶面相比,{111}晶面氧密度较低,同时具有更多的开放性孔道。阳离子染料RhB和阴离子染料MO的吸附实验进一步证实了{111}晶面的原子结构特征。由UV-vis光谱结合Mott-Schottky曲线得到BiOBr-111和BiOBr-001的能带结构。与BiOBr-001相比,BiOBr-111的禁带宽度更窄,而且导带底和价带顶均上移,这有利于光的吸收以及光生电子和空穴的有效分离。可见光下降解染料和气态丙酮实验,以及光电性能测试均表明BiOBr-111具有比BiOBr-001更优异的光催化和光电催化性能。（3）为了进一步提高BiOBr的量子效率,拓宽其应用范围,我们通过水热法结合化学沉淀法得到BiOBr纳米片@TiO₂纳米带异质结。Mott-Schottky曲线证实在BiOBr和TiO₂接触面上形成了p-n结。可见光照射下,BiOBr@TiO₂ p-n结可以还原水生成H2。光解水和光降解RhB的实验表明,BiOBr@TiO₂ p-n结比纯BiOBr和纯TiO₂具有更高的光催化活性。更多还原

【Abstract】 The development of high-efficiency photocatalysts is a core part in the photocatalysis.However,there are two bottlenecks hindering the application of photocatalytic technology.One is the high recombination rate of the photo-induced electron-hole pairs;the other is the low utilization of solar energy.As alternative photocatalysts,BiOX（X=Cl,Br,I）have attracted considerable attention owing to their special crystal structure and electronic structure,strong visible-light absorption,low toxicity as well as high stability.In this study,the photocatalytic activity of BiOBr was optimized by tailoring morphology,facet-controlled fabrication and semiconductor coupling.The main research results can be summarized as follows.（1）Hierarchical BiOBr microspheres were synthesized via a facile solvothermal route in the presence of anionic surfactant sodium dodecyl sulfate（SDS）.To the best of our knowledge,it is for the first time to prepare BiOX with the assistance of anionic surfactant.SEM and TEM results showed that the 2D nanosheets,which were self-assembled to form the 3D structures,were achieved with the thickness decreasing from average 160 nm to 25 nm,and that the size of crystal particles was smaller in the presence of SDS.XPS results showed that the BiOBr products with the assistance of SDS had more O-vacancy.Photocatalytic activity of the as-prepared BiOBr samples was evaluated by the photocatalytic degradation of RhodamineB（RhB）under visible light irradiation.The BiOBr in the presence of SDS exhibited higher photocatalytic activity than that in the absence of SDS.（2）Based on the above studies,we obtained 3D flower-like BiOBr nanostructures by changing the concentration of Bi（NO₃）₃·5H₂O and KBr.The as-prepared BiOBr was self-assembled by 2D nanosheets which were partially enclosed by {111} facets due to the effect of SDS.To the best of our knowledge,it is the first report about {111} facets of BiOX.Compared with {001} facets of BiOBr,{111} facets exhibited open channel feature and had lower density of oxygen atoms,which was further confirmed by the adsorption of cationic dye RhB and anionic dye MO.UV-vis diffuse reflectance spectroscopy and Mott-Schottky curves showed that the band gap of BiOBr-111 was narrower than that of BiOBr-001,and both the CB and VB of BiOBr-111 up-shifted,which was beneficial to the separation of photo-induced electron-hole pairs.The as-prepared BiOBr with {111} facets exhibited excellent electrochemical behavior and photocatalytic activity under both visible light（λ≥420 nm）and monochromatic light（λ=420 nm）irradiation.（3）In order to improve the quantum efficiency of BiOBr and widen its application,BiOBr nanosheet@TiO₂ nanobelt p-n junction photocatalysts were prepared by assembling BiOBr nanosheets on the surface of TiO₂ nanobelts via a hydrothermal route followed by a co-precipitation process.Mott-Schottky plots confirmed the formation of p-n junctions in the interface of BiOBr and TiO₂.BiOBr@TiO₂ p-n junction photocatalysts exhibited enhanced photocatalytic activity in photocatalytic H2 production over water splitting and the photodegradation of RhB under visible light irradiation.This work showed a potential application of low cost BiOBr as a substitute for noble metals in photocatalytic H2 production under visible light irradiation.更多还原