光驱动多孔无定形TiO2的形成机制与光催化性能的研究

Investigation on the Light-Driven Formation Mechanism and Photocatalytic Properties of a Porous Amorphous Titanium Dioxide

以钛酸正丁醇和乙二醇为原料,采用溶剂热法合成了钛乙二醇盐(TG)前躯体,在高压汞灯照射下制备出无定形TiO2。利用X射线衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)、紫外-可见吸收光谱(UV-Vis)、表面光电压谱(SPS)、N2吸附-脱附对所得材料进行了结构和性能的表征。借助X射线吸收精细结构(XAFS)对无定形TiO2的形成机制进行了分析,并通过硝基苯的还原反应考察了材料的光催化性能。结果表明:在紫外光驱动无定形TiO2的形成过程中,中心元素Ti4+的配位环境发生变化,由八面体结构转变为四面体结构;由于特殊的孔道结构使得多孔无定形TiO2显示出较好的光催化活性。

A porous amorphous TiO2 has been prepared through a light-driven formation process. Titanium glycolate （TG） synthesized through the solvothermal reaction between titanium （IV） n-butoxide and ethylene glycol is used as a precursor. The irradiation of TG under UV light leads to the formation of the porous amorphous TiO2. The sample is characterized by powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and N2 adsorption/desorption. The results of these characterizations reveal the porous and amorphous nature of the sample. The transformation mechanism from TG to amorphous TiO2 under UV light is investigated by X-ray absorption fine structure （XAFS） spectroscopy. Extended X-ray Absorption Fine Structure （EXAFS） and X-ray absorption near edge structure （XANES） spectra indicate that the transformation from TG to porous amorphous TiO2 is accomplished through the configuration conversion of titanium species. The configuration of titanium species changes from octahedron to tetrahedron due to the breakage and reconstruction of Ti-O bonds under UV irradiation. The photocatalytic properties of the porous amorphous TiO2 are evaluated based on the reduction of nitrobenzene. As indicated by the surface photovoltage spectroscopy （SPS）, the separation of photogenerated charges can be facilitated by the porous structure of the amorphous TiO2, resulting in the high photocatalytic activity of the sample.