One-Pot Miniemulsion-Mediated Route to BiOBr Hollow Microspheres with Highly Efficient Photocatalytic Activity
One-Pot Miniemulsion-Mediated Route to BiOBr Hollow Microspheres with Highly Efficient Photocatalytic Activity
复制标题
一锅法细乳液介导制备具有高效光催化活性的 BiOBr 空心微球
DOI：
10.1002/chem.201100564
复制
发表时间：
2011-07-01
影响因子：
4.3
通讯作者：
Dai, Ying
中科院分区：
文献类型：
--
作者：
Cheng, Hefeng;Huang, Baibiao;Dai, Ying
由于无机材料具有形状依赖的物理化学性质，其有序结构的合成方法一直是材料化学研究的热点。特别是，人们已经注意到的分层宏观，介观，或具有中空空隙的微结构的自组装，具有纳米尺寸的积木和有组织的架构的组合特征，凭借其在药物输送，锂离子电池和催化方面的潜在应用。[1]许多合成方法已被用来加速实现特殊的微结构。例如，传统的模板导向合成被证明是一种通用且有效的方法，其中使用硬或软模板，如聚合物载体，[2]碳球[3]和有机表面活性剂[4]来定制生长过程。然而，模板导向的路线通常受到繁琐的程序和可能引入的杂质。理想情况下，人们更喜欢无模板路线，而不是内部中空的无机材料。作为模板剂的替代途径，乳液和细乳液体系（其在化学上是不稳定的）已被用于制备中空结构。[5-8]由于混合溶剂的溶解性有限，通过超声或搅拌的微非均相性产生了可用作微反应器的微米级至甚至更大的乳液。[9，10]然而，大多数合成需要大量的表面活性剂来产生胶束，从而增加了复杂性，并且中空结构的一锅法合理控制仍然是一个挑战。近年来，半导体催化剂被认为是一种有效的制氢和去除有机污染物的方法。[11-17]然而，传统的半导体TiO 2和WO 3受到其可见光吸收不足或光生载流子的高复合率的限制。[11在寻找高活性光催化剂的过程中，人们一直致力于带隙调节和量子效率的提高。作为一种三元半导体，BiOBr以[Bi 2 O2] 2+层与双溴层交织组成的分层结构结晶。此前，BiOBr在降解有机污染物方面表现出相当大的可见光光催化性能。[18]到目前为止，各种BiOBr纳米/微米结构，包括纳米片，纳米带和微球，已经通过许多方法制造。[18然而，控制BiOBr构建单元（如纳米片）自组装成其中空结构仍然是一个瓶颈。此外，BiOBr的光催化活性远不能满足实际应用的需要，必须通过微结构调控来提高其光催化效率。本文报道了在离子液体1-十六烷基-3-甲基咪唑溴化物（[C16 Mim] Br）和2-甲氧基乙醇的混合溶剂中，采用一锅法制备直径为1-2 μm、壳层厚度为100 nm的BiOBr中空微球的方法。这些HMS在可见光照射下表现出高效的光催化活性，降解罗丹明B（RhB）染料和还原CrVI。含Br离子液体不仅作为溴化物源，而且还产生胶体细乳液，这通过观察到的前体悬浮液的廷德尔效应得到证实（参见支持性信息中的图S1）。反应发生在细乳液的相界面上，而不是在乳液本身中，从而保持了微乳液的尺寸。
Due to the shape-dependent physical/chemical properties of inorganic materials, methodological syntheses of their ordered architectures have always been the hotspots in materials chemistry. In particular, attention has been paid to the self-assembly of the hierarchical macro-, meso-, or microstructures with hollow voids, which possess the combined features of nanosized building blocks and the organized architectures, in virtue of their potential applications in drug delivery, lithium-ion batteries, and catalysis.[1] Numerous synthetic methods have been exploited to accelerate the realization of special microstructures. For example, the conventional template-directed synthesis turns out to be a universal and effective approach, in which hard or soft templates, such as polymer supports,[2] carbon spheres,[3] and organic surfactants [4] are employed to tailor the growth process. Nevertheless, the template-directed routes usually subject to the tedious procedures and possible impurities introduced. Ideally, people would prefer template-free routes to the inorganic materials with hollow interiors. As an alternative route to templates, emulsion and miniemulsion systems, which are thermodynamically instable, have been employed to produce hollow structures.[5–8] Derived from the limited miscibility of the mixed solvents, microsized to even larger emulsions, which can perform as the microreactors, are produced by the micro-heterogeneities by means of sonicating or stirring.[9, 10] However, most of the syntheses require large quantities of surfactants to generate micelles, thereby increasing the complexity, and one-pot rational control of the hollow architectures still remains a challenge. Recently, semiconductor photocatalysis has been regarded as an effective resolution to the hydrogen production and organic pollutants removal.[11–17] The conventional semiconductors, TiO2 and WO3, however, are restricted by their deficient visible-light absorption or high recombination rate of the photogenerated carriers.[11, 14] In search of highly visiblelight-active photocatalysts, great efforts have been dedicated to the bandgap regulation and quantum efficiency improvement. As a ternary semiconductor, BiOBr crystallizes in a layered structure composed of [Bi2O2] 2+ layers interleaved with double Br layers. Previously, BiOBr has exhibited considerable visible-light photocatalytic performance in the degradation of organic contaminants.[18] So far, a variety of BiOBr nano/micro-structures, including nanoplates, nanobelts, and microspheres, have been fabricated by numerous methods.[18, 19] However, controlling the self-assembly of the BiOBr building units, such as nanosheets, into their hollow architectures is still a bottleneck. Moreover, the photocatalytic activity of BiOBr is far from efficient for practical applications and it is indispensable to boost the photocatalytic efficiency by microstructure modulations. Herein, we report a facile one-pot approach to the uniform BiOBr hollow microspheres (HMSs), with a diameter of 1–2 μm and shell thickness of% 100 nm, in a mixture of 2-methoxyethanol and the ionic liquid (IL) 1-hexadecyl-3-methylimidazolium bromide ([C16Mim] Br). These HMSs display highly efficient photocatalytic activities in the degradation of RhodamineB (RhB) dye and reduction of CrVI under visible-light irradiation. The Br-containing ILs function not only as the bromide source, but also gives rise to colloidal miniemulsions, confirmed by the observed Tyndall effect of the precursor suspension (see Figure S1 in the Supporting Information). The reaction takes place at its phase interface of the miniemulsion rather than in the emulsion itself, thus maintaining the dimensions …