磷钨酸钾模板法制备高活性二氧化钛空心微球（英文）

Fabrication of TiO_2 hollow microspheres using K_3PW_(12)O_(40) as template

TiO2空心微球因具有低密度、高活性、易分离而有利于多次重复使用的优点而广受关注.本文介绍一种无氟制备TiO2空心微球的简单方法——磷钨酸钾(K3PW12O40)模板法.首先,将H3PW12O40和KCl溶液混匀,得到白色牛奶状的K3PW12O40模板(式(1)),然后在磁力搅拌下加入一定量的Ti(SO4)2粉末,加热至大约125 oC开始回流.回流8 h后,过滤洗涤.滤饼分散在强NaO H溶液中,原位除去K3PW12O40模板(式(2)).最后,将催化剂洗涤到滤液为中性,干燥后即得到TiO2空心微球.3KCl+H3PW12O40=K3PW12O40↓+3HCl(1)K3PW12O40+24Na OH=12Na2WO4+K3PO4+12 H2O(2)Ti(SO4)2+2H2O=Ti O2+2H2SO4(3)我们将所制备的Ti O2空心微球,采用X射线衍射、透射电子显微镜、扫描电子显微镜、傅立叶红外光谱、固体粉末漫反射和X射线光电子能谱等进行了表征.采用紫外光催化降解阴离子染料(活性嫣红X3B)来评价催化剂的性能.实验结果显示:(1)所制Ti O2空心微球直径在0.5–1.0μm;(2)磷钨酸钾模板剂充当晶核,有利于空心微球的晶化;(3)加入的高浓度硫酸钛,水解产生大量的硫酸,抑制硫酸钛水解,不利于Ti O2空心微球的晶化(式(3));(4)催化剂的活性随着硫酸钛量的增加而先增后降.4 mmol硫酸钛用量的Ti O2空心微球具有最高的光催化活性,是Ti O2颗粒样品(无磷钨酸钾模板法制备)的2.1倍.用该方法制备的Ti O2空心微球活性高可归因于以下主要原因:(1)Ti O2空心微球独特的孔结构;(2)良好的晶化程度(TiO2样品晶化度越高,越有利于光生载流子的分离,抑制复合);(3)样品残余磷钨酸钾模板和Ti O2之间存在光生电子转移,有利于空心微球Ti O2活性的提高.该法具有操作简单、重复性好、易于批量制备的等优点,有望广泛应用于(光)催化、电化学、分离与纯化以及药物缓释等领域.

Fabrication of TiO 2 hollow microspheres（TiO 2-HMSs） has attracted considerable attention owing to their low density,high photoreactivity,and easy to separate and reuse. A fluoride-free method for the fabrication of TiO 2-HMSs is reported by refluxing a mixed solution of H3PW12O40（0.4 mmol）,KCl（2.5 mmol） and Ti（SO4）2（2–25 mmol） at 125 °C for 8 h,followed by decomposition of the K3PW12O40（KPW） template in basic solution. The prepared TiO 2-HMSs are characterized by X-ray diffraction,transmission electron microscopy,scanning electron microscopy,Fourier transform infrared spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The activities of the photocatalysts are evaluated by photocatalytic degradation of Brilliant Red X-3B,an anionic dye,under UV irradiation. It is observed that the TiO 2-HMSs exhibit diameters of approximately 0.5–1 μm,and the photocatalytic activity of TiO 2-HMSs initially increases and then decreases with an increasing amount of Ti（SO4）2. The TiO 2-HMSs prepared in the presence of 4 mmol Ti（SO4）2 exhibit the highest photocatalytic activity,which is 2.1 times higher than TiO 2 nanoparticles（prepared in the absence of the KPW template）. The enhanced photocatalytic activity of the prepared TiO 2-HMSs is ascribed to the improved crystallization,coupling effect between TiO 2and the residual KPW template,and the unique hollow structures of TiO 2-HMSs.