【作者】 石睿；

【导师】 朱永法；

【作者基本信息】 清华大学 ， 化学， 2011， 博士

【摘要】 开发具有高能效及高活性的新型光催化剂是光催化研究领域的重要方向，本论文主要是通过两种手段来提高这两方面的性能：①复合氧化物纳米粒子的调控合成；②阴离子取代复合氧化物。纳米形貌调控在很大程度上可以改变化合物的物理化学性能，而具有纳米尺寸的光催化剂一般具有特殊的形态，高的比表面积和高效的电子-空穴分离率，因此通常具有很高的光催化活性；而对于阴离子取代的复合氧化物光催化剂来说，阴离子取代可以使其光响应范围大幅度红移，以便充分利用可见光，因此可以提高其光催化能效。在本论文工作中，通过无模板的水热合成路线，可以制备不同形貌的Zn₃V₂O₇（OH）₂（H₂O）₂纳米粒子，并且首次评价了其光催化活性，结果证明在低温合成的自主装纳米花球状晶体其催化活性最好，在紫外光照射80分钟内可以将亚甲基蓝降解完全。通过适当煅烧Zn₃V₂O₇（OH）₂（H₂O）₂使其脱水，可以制备可见光型Zn₃V₂O₈自组装孔状纳米花球光催化剂，通过活性评价证明此样品对亚甲基蓝的降解速率常数是传统高温固相所合成Zn₃V₂O₈的3倍。采用相同的水热合成方法，可以制备不同形貌的ZnWO4纳米粒子，光催化评价结果显示不同形貌的ZnWO₄具有不同的光催化活性，其中长径比值最大的ZnWO4纳米棒的催化活性最优，在紫外光照射50分钟内可以将亚甲基蓝降解完全。表征结果显示此纳米棒沿[100]方向生长，并且沿[100]方向平行生长的两个晶面—（010）和（011）面是光催化的活性面。通过加热回流方法可以成功制备氟离子取代Bi₂WO₆（Bi-2WO——6-XFX）光催化剂。氟离子取代改变了原有Bi₂WO₆中W和Bi原子的配位环境，并且与Bi2WO6相比，在可见光照射下对亚甲基蓝的降解活性增加了1.5倍。理论计算和实验数据证明Bi₂WO₆-XFX的高活性来源于其能带结构特征以及具有更强氧化性的光生空穴。同样采用加热回流的方法可以制备硫离子取代的Bi₂MoO₆（Bi₂MoS₂O₄）光催化剂。同Bi₂MoO₆相比，Bi₂MoS₂O₄对可见光的响应范围由原来的470nm扩展到630nm，并且在很大范围的可见光内都具有优良的光催化降解能力。Bi₂MoS2O₄的高能效特点是由于S3p轨道参与了价带的构成，从而减小了原有的能带间隙。并且这种加热回流的合成方法可以为我们以后设计和制备其他阴离子取代化合物提供一种思路。更多还原

【Abstract】 Developing novel photocatalysts with high energy efficiency and high activity isvery important for photocatalytic research. In our work, composite metal oxidenanocrystals with tailored shape and composite metal oxide by anion substitution wereadopted to realize this aim. Nanostructured photocatalysts usually have highphotocatalytic activities because of their special morphologies, high surface areas andhigh efficiency of electron-hole separation. And from the viewpoint of solar energyutilization, one effective way to narrow the band gap of photocatalyst is to elevate thevalence band of photocatalysts into a more negative position by anion substitution.Zn₃V₂O₇（OH）₂（H₂O）₂nanocrystals with various morphologies were successfullysynthesized by a template-free hydrothermal route. Significantly, this is the first timethat Zn₃V₂O₇（OH）₂（H₂O）₂was used as a photocatalyst for organic pollutant degradationunder UV light irradiation. It was found methylene blue could be fully degraded byfloriated like nanostructures of Zn₃V₂O₇（OH）₂（H₂O）₂less than80min. Moreover,Zn3V2O8with porous floriated like nanostructures could be formed via calcination ofthe corresponding Zn₃V₂O₇（OH）₂（H₂O）₂. The reaction constant of the best qualityZn3V2O8nanostructure was three time that of the sample prepared by solid-statereaction under visible-light irradiation.ZnWO₄photocatalysts with various morphologies could also be successfullysynthesized by a template-free hydrothermal route. The morphologies had a significantinfluence on the photocatalytic activity. ZnWO₄nanorods with maximal aspect ratioexhibited the highest photocatalytic activity among all the samples, methylene bluecould be degraded less than50min under UV light irradiation. This ZnWO₄nanorodsgrew preferentially along the [100] direction, and the two planes along the [100]direction—（010） and （011） planes could be speculate to be more active forphotodegradation.F^-substituted Bi₂WO₆（Bi₂WO₆-XFX） photocatalysts with high activity could besynthesized by reflux method. F-substitution could change the original coordinationaround the W and Bi atoms. Comparing with Bi₂WO₆, the photocatalytic activity ofBi₂WO₆-XFXincreased about1.5times for degradation of MB under visible-light irradiation. Density functional calculations and experiment revealed that the highactivities of Bi₂WO₆-XFXphotocatalysts come from its special band structure whichincrease the mobility of photoexcited charge carriers and possess a stronger oxidationpower.S^2-substituted Bi2MoO6（Bi2MoS2O4） photocatalysts with high energy efficiencycould be synthesized by reflux method. The visible-light response of Bi₂MoS₂O₄couldextend from470to630nm compared with Bi₂MoO₆. Moreover, Bi₂MoS₂O₄possessexcellent photocatalytic activities in the broad range under visible light. Densityfunctional calculation revealed that Bi₂MoS₂O₄had narrower band gap compared withBi2MoO6because S3p orbital contributed to the valence band formation. Furthermore,this reflux method could afford guidance for designing and synthesizing the other anionsubstitution photocatalysts.更多还原