Structure Tuning of Bi2MoO6 and Their Enhanced Visible Light Photocatalytic Performances

Structure-tuning strategies for synthesis and modification of Bi₂MoO₆, a novel visible light photocatalyst, have progressed at a quick pace. The enhancement of photocatalytic performances has been obtained through several morphology controls including hierarchical structures and heterojunctional nanocomposites. In this article, various structure modifications and their structural advantages in photocatalysis will be reviewed. In the first section, the structures of Bi₂MoO₆ such as crystal structures, electronic structures, and band structures will be presented. In the second section, many controllable synthesis approaches for modification of Bi₂MoO₆, including solid-state reaction, co-precipitation, solvothermal, and hydrothermal methods will be introduced. In the last section, the enhancement of photocatalytic activity for Bi₂MoO₆ due to the structure tuning will be discussed. The comprehensive review will provide perspectives on the research of efficient photocatalysts under visible light irradiation.     

氮自由基化学新进展:光催化N-H键活化途径

氮自由基作为一种高活性的中间体,为新型化学反应的设计及含氮化合物的合成提供了新的机遇.光催化条件活化N-H键直接产生氮自由基具有绿色、高效、经济等优点,相关方法学的研究在近年来取得了重要进展.本综述就2016年至今报道的几例最新的研究成果进行亮点评述.     

Carbon nanotubes/TiO2 nanotubes composite photocatalysts for efficient degradation of methyl orange dye

A series of carbon nanotubes/TiO2 nanotubes （CNTs/TNTs） composite photocatalysts were successfully prepared by incorporation of CNTs in HNO3 washing process. These photocatalysts were characterized by XRD, N2 physical adsorption, UV-vis diffuse reflectance spectroscopy, TEM and Raman spectroscopy, respectively, and their photocatalytic activities were tested by using methyl orange （MO） as a model compound. Also, the effects of amount of CNTs incorporated, calcination temperature and amount of catalyst on the photocatalytic activity of the composite photocatalyst were systematically investigated. The results show that the CNTs/TNTs composite exhibits much higher photocatalytic activity than that of the TNTs or CNTs alone.     

Visible light photodegradation of methylene blue by AgBr-TiO2/SiO2@Fe3O4 magnetic photocatalysts

Visible photoactive AgBr/TiO2 was immobilized on a SiO2@Fe3O4 magnetic support by solvother- rnal and sol-gel methods to form a AgBr-TiO2/SiO2@Fe3O4 magnetic photocatalyst. Samples were characterized by X-ray diffraction, high-resolution transmission electron microscopy and magne- tometry. Hereto-structured AgBr/TiO2 was well seeded on the shell-core SiO2@Fe3O4 structure. The AgBr-TiO2/SiO2@Fe3O4 magnetic photocatalyst exhibited high photocatalytic activity in the degrada- tion of methylene blue under visible light. The photocatalyst was superparamagnetic, which is beneficial for facile magnetic separation.     

在一种新的溶剂体系中通过静电纺丝制备TiO2纳米纤维

以钛酸四丁酯为前驱体, 醋酸纤维素为模板纤维, 丙酮/N,N-二甲基乙酰胺为溶剂, 通过静电纺丝, 水解和450 ℃煅烧制备了直径约为80 nm的锐钛矿型TiO₂纳米纤维. 通过扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)和N₂吸脱附法表征了TiO₂纳米纤维的形貌、直径大小、晶态、比表面积、孔结构及分布. 研究表明该纳米纤维由大小为9.2 nm的颗粒组成, 纤维内含有大量直径为1.7～21 nm的介孔. 它具有与直径为25 nm的商业化Degussa P25相似的高比表面积, 约为50 m²/g. 研究了TiO₂纳米纤维对有机小分子化合物罗丹明B (RhB)和苯酚的光催化降解. 结果表明: 以6 mg/L的RhB和10 mg/L的苯酚水溶液为母液, 以质量分数为0.05%的TiO₂纳米纤维膜为催化剂, 在500 W的紫外灯照射下, 2 h内约90%的RhB和75%的苯酚能被光催化降解.     

高分子模板对CdS量子点制备及其光催化性能的影响

分别以球形聚酰胺-胺(PAMAM)树形分子和线形聚乙烯吡咯烷酮(PVP)两种结构不同的高分子为模板, 原位制备了分散良好的CdS量子点(CdS QDs), 并以甲基橙为降解对象, 研究了高分子模板结构对CdS量子点的制备和光催化性能的影响. 结果表明, 以PAMAM 树形分子为模板制备的CdS量子点(CdS QDs/PAMAM)比以PVP为模板制备的CdS量子点(CdS QDs/PVP)的尺寸分布更窄, 激子吸收峰更明显, 光致发光(PL)强度更高|并且在量子点尺寸接近的情况下, CdS QDs/PAMAM的催化效率明显高于CdS QDs/PVP. 这是由于PAMAM树形分子独特的结构有利于生成尺寸均匀的CdS量子点, 且不易钝化量子点表面的活性位点|而线性的PVP分子量分布较宽, 使制备的量子点的尺寸分布较宽, 且PVP分子链缠绕在CdS量子点表面, 钝化了部分活性位点, 降低催化效率. 此外, CdS QDs/PAMAM的催化能力随粒径减小而增大.     

可见光促进的双键三氟甲基化反应研究

报道了一种可见光促进的双键直接三氟甲基化的方法.研究中利用Ru（bpy）₃Cl₂为催化剂,Togni's试剂为三氟甲基来源,在可见光促进下实现了含羰基烯烃的三氟甲基化.该反应具有方法简便,条件温和,可以获得较高的反应收率,同时避免了有毒试剂的使用.     

ZnWO4-ZnO复合光催化剂的制备及光催化性能

以ZnO及WO3为前驱反应物,制备了一系列不同ZnWO4含量的ZnWO4-ZnO复合光催化剂.利用X射线衍射、扫描电子显微镜及X射线能谱仪等手段对催化剂进行表征,并以紫外光为光源,罗丹明B为模拟污染物,评价催化剂的活性.结果表明,热处理温度及ZnWO4与ZnO摩尔比对催化剂光催化降解罗丹明B的活性影响显著.当复合4mol;ZnWO4,并于850 ℃煅烧所制得的ZnWO4-ZnO催化剂活性最高,比纯ZnO高出25;.这是因为ZnWO4的复合可抑制ZnO晶粒长大,提高光生电子与空穴的分离效率,进而改善其光催化活性.     

ZnO-SiO2的制备及其光催化降解罗丹明B

采用溶胶-凝胶法制备负载型ZnO-SiO2光催化材料,研究升温速率及负载量对ZnO结构、形貌及光催化活性的影响.通过X射线衍射、N2物理吸附-脱附、扫描电子显微镜、光致发光光谱和紫外-可见漫反射光谱等手段对催化剂进行表征,并以罗丹明B为模拟污染物,紫外光为光源,评价催化剂活性.结果表明,升温速率对ZnO-SiO2光催化剂结晶度和光催化活性影响显著.当ZnO与SiO2的质量比为1∶1时,ZnO-SiO2具有均匀、平滑的球形形貌,并且ZnO光催化活性明显改善.     

介孔碳负载Ce-TiO2的制备及其光催化降解亚甲蓝性能

以Ce(NO3)3·6H2O、一水合柠檬酸、2-羟基对苯二甲酸、N,N-二甲基甲酰胺(DMF)、钛酸四丁酯为原料,通过水热法获得一种新型的Ce-Ti金属有机材料前驱体,将该前驱体在不同烧结温度下煅烧,获得一系列具有高比表面积的介孔碳负载Ce-TiO2新型催化剂.应用XRD、SEM、BET、TG、UV-vis DRS、UV紫外吸收等一系列手段对其进行了结构表征与性能测量.研究结果表明烧结温度在1000 ℃(CTOF-P10)的样品表现出良好的催化效果,其降解亚甲蓝(MB)的速率是商业型TiO2(P25)的2.15倍.引入Ce离子起到掺杂的作用,同时阻止TiO2晶粒的生长,也能抑制光生电子与空穴的复合,进而提高了光催化活性.