Anatase TiO2 Crystals with Exposed High-Index Facets
Anatase TiO2 Crystals with Exposed High-Index Facets
复制标题
具有外露高折射率刻面的锐钛矿型 TiO2 晶体
DOI：
10.1002/anie.201007771
复制
发表时间：
2011-01-01
影响因子：
16.6
通讯作者：
Yang, Hua Gui
中科院分区：
文献类型：
--
作者：
Jiang, Hai Bo;Cuan, Qian;Yang, Hua Gui
Inorganic functional materials with tailor-made crystal facets have attracted great research interest owing to their applications in catalysis, sensors, batteries, and environmental remediation.[1–6] Unfortunately, the surfaces with high reactivity usually diminish rapidly during the crystal growth process as a result of the minimization of surface energy. Thus, increasing the percentage of known highly reactive surfaces or creating new favorable surfaces is highly desirable. Crystalline titanium dioxide (TiO2) in the anatase phase is one of the most important semiconducting metal oxides, owing to its many promising energy and environmental applications.[7–9] Conventionally, anatase TiO2 crystals are dominated by the thermodynamically stable {101} facets (ca. 94 percent, according to the Wulff construction) and a minority of {001} facets.[10] Recently, we developed a new strategy to synthesize anatase TiO2 crystals with a large percentage of highly reactive {001} facets using fluorinecontaining compounds, such as hydrofluoric acid, as capping agents, which made {001} energetically preferable to {101}.[4] Gas-phase reactions with rapid heating and quenching were also reported recently to generate {001}-faceted decahedral anatase TiO2 crystals.[11] Most recently, photocatalytically active {100} facets of anatase TiO2 crystals were synthesized using solid sodium titanates as the titanium source under hydrothermal conditions.[12] However, all these breakthroughs contribute to the increase of the percentage of known low-index {001} or {100} facets only, which are the basic crystal surfaces in the Wulff construction model of anatase in a thermodynamically stable state and have been evidenced theoretically and experimentally.[13] Because they usually have unique surface atomic structures, such as a high density of atomic steps, dangling bonds, kinks, and ledges, that can act as active sites, high-index planes of anatase may have the capability to be used in clean-energy and environmental applications. Unfortunately, owing to the high surface energies, which can lead to the elimination of high-index crystal planes, it is still an open challenge to synthesize tailor-made anatase TiO2 crystals bounded by highindex facets. Herein we report a facile process to prepare well-defined anatase TiO2 crystals with predominantly exposed high-index {105} facets, which have never been realized experimentally before. The anatase TiO2 crystals with exposed high-index {105} facets were prepared by a modified high-temperature gasphase oxidation route using titanium tetrachloride (TiCl4) as the Ti source.[11] A schematic reaction apparatus is given in Figure S1 in the Supporting Information. A straight static furnace pipe and a thin spiral tube were used as reactor and reactant feeder, respectively. In a typical experiment, the vapor-phase TiCl4 was liberated by bubbling oxygen (0.2 L minÀ1) into TiCl4 liquid at 988C and then passed through the furnace pipe at a temperature of 10008C. The experimental process was shown to be quite robust, and the reproducible synthesis of the anatase TiO2 crystals with exposed high-index {105} facets was also confirmed. Moreover, key synthesis conditions such as concentration of titanium precursor, reaction temperature, and oxygen flow were also explored extensively. In all experiments, the final white products were collected downstream by a bag filter and washed with deionized water three times to remove the adsorbed chlorine-containing species on the surface. Gramscale production can be easily achieved if a furnace pipe with a diameter of about 5 cm is used (Figure S2 in the Supporting Information for digital camera images of the …
