Single-Crystal-like Titania Mesocages
Single-Crystal-like Titania Mesocages
复制标题
类单晶二氧化钛介孔
DOI：
10.1002/anie.201004972
复制
发表时间：
2011-01-01
影响因子：
16.6
通讯作者：
Lu, Yunfeng
中科院分区：
文献类型：
--
作者：
Bian, Zhenfeng;Zhu, Jian;Lu, Yunfeng
二氧化钛代表了用于光催化剂和光催化剂的最广泛使用的氧化物半导体，[1-12]并且其性能在很大程度上受其表面积和暴露的晶面控制。[13-18]然而，迄今为止，所制备的TiO 2样品仅限于具有低表面积的单晶或暴露其活性较低的平面的多孔多晶。本文报道了具有可控介孔网络和高活性（001）面优先暴露的高比表面积、类Ersex介孔材料的合成。这种简单的溶液生长方法可以很容易地扩展到合成除TiO 2之外的其他介孔单晶，为催化，能量储存和转换以及其他应用提供了一类新的材料。TiO 2的光催化活性通常取决于其晶体结构。[13-19]例如，晶体的（001）面比（101）面更活跃，后者是晶体中最常见的和晶体学上更稳定的晶面。[19]因此，大量的努力致力于合成具有优先（001）面暴露的TiO 2晶体。[5，13-18]与晶体学控制一样，同样重要的是在晶体内构建孔网络以增加表面积并提供孔依赖性活性和选择性。[20-22]迄今为止，尽管已经使用溶胶-凝胶和软或硬模板方法制备了大量多孔TiO 2，[1，6，8，21，23-25]目前的材料限于具有无定形或多晶骨架的多孔TiO 2，其表现出低的光催化活性和电荷传输能力。在这里，使用晶体定向生长的方法，我们报告的合成高活性的介孔的，具有优先的（001）平面暴露和可控的介孔网络的Erse介孔状TiO 2（mesocages）。如图1所示，我们从含有SO 4 2的前体溶液开始;溶剂热反应生成TiO 2构建晶体，其（001）平面优选被SO 4 2阴离子吸附。建筑晶体的附着生长产生了具有受保护的（001）面的晶体簇（步骤1）。进一步生长导致具有优先（001）平面暴露和源自构建晶体之间的空隙的无序中孔网络的TiO 2晶体（步骤2）。为了构建有序介孔通道，将生长限制在具有有序孔道的支架内，例如含有2D（SBA-15，P6 mm空间群）和3D（KIT-6，Ia 3d空间群）有序介孔的二氧化硅。随后的支架去除分别导致具有复制的2D六边形结构（步骤3）或3D（步骤4）有序网络结构的TiO 2晶体。具有无序介孔结构的TiO 2晶体显示出600 nm的平均直径（图2a），并且由平均直径为8.0 nm的组分晶体组成（图2b）。TEM图像清楚地显示了无序的中孔结构（图2c）;然而，在晶体上记录的选区电子衍射（SAED）图案（插图）显示了单-双折射的衍射图案。
Titania represents the most widely used oxide semiconductor for photocatalysts and photovoltaics,[1–12] and its performance is heavily governed by its surface area and the exposed crystal planes.[13–18] To date, however, as-made TiO2 samples have been limited to the single crystals with low surface area or porous polycrystals exposing their less-active planes. We report herein the synthesis of high-surface-area, singlecrystal-like anatase with controlled mesoporous network and preferential exposure of the highly active (001) planes. This simple solution-growth method is readily extendable to the synthesis of other mesoporous single crystals beyond TiO2, providing a new class of materials for catalysis, energy storage and conversion, and other applications. The photocatalytic activity of TiO2 is generally dependent on its crystallography.[13–19] For example, the (001) planes of anatase are much more active than the (101) planes, which are the most commonly observed and thermodynamically more stable crystalline planes in the anatase form.[19] Significant effort has therefore been devoted to synthesize TiO2 crystals with preferential (001) plane exposure.[5, 13–18] As well as crystallographic control, equally important is building networks of pores within the crystals to increase the surface area and provide pore-dependent activity and selectivity.[20–22] To date, although a large number of porous TiO2 have been made using sol–gel and soft- or hard-templating approaches,[1, 6, 8, 21, 23–25] the current materials are limited to porous TiO2 with amorphous or polycrystalline frameworks that exhibit low photocatalytic activity and charge-transport capability. Herein, using a method of crystal oriented growth, we report the synthesis of highly active mesoporous, singlecrystal-like TiO2 (mesocages) with both preferential (001) plane exposure and controllable mesoporous networks. As illustrated in Figure1, we started with precursor solutions containing SO4 2À; solvothermal reactions generate TiO2 building crystals of which the (001) planes are preferably adsorbed by the SO4 2À anions. Attached growth of the building crystals created crystal clusters with the protected (001) planes (step 1). Further growth led to TiO2 crystals with preferential (001) plane exposure and disordered mesoporous networks that originate from the voids among the building crystals (step 2). To construct an ordered mesoporous channels, the growth was confined within a scaffold with ordered pore channels, such as the silica containing 2D (SBA-15, P6mm space group) and 3D (KIT-6, Ia3d space group) ordered mesopores. Subsequent scaffold removal resulted in TiO2 crystals with replicated 2D hexagonal structure (step 3) or 3D (step 4) ordered network structure, respectively. The TiO2 crystals with disordered mesoporous structure show an average diameter of 600 nm (Figure 2a), and are composed of component crystals with an average diameter of 8.0 nm (Figure 2b). The disordered mesoporous structure is clearly shown by the TEM image (Figure 2c); nevertheless, a selected-area electron diffraction (SAED) pattern recorded on the crystal (inset) shows a diffraction pattern of single-