TiO_2纳米粒子的制备和表征及光催化活性

Preparation and characterization of TiO_2 nanoparticles and their photocatalytic activity

以钛酸四丁酯为原料,采用溶胶-凝胶法制备了TiO2纳米粒子,利用XRD,TEM,SPS,XPS,PL和UV-VIS测试技术对样品进行了表征。考察了TiO2样品的微晶尺寸、晶型结构、表面组成、光电性能和光学性能以及焙烧温度对TiO2粒子性质的影响。结果表明:随着焙烧温度升高,TiO2纳米粒子完成了相转变过程,并表现出量子尺寸效应。600℃焙烧的TiO2纳米粒子具有与国际商品P-25型TiO2粒子相类似的晶相组成、结构、形貌和粒子尺寸,并且表面含有一定量的氧空位,这解释了表面有一定量的羟基氧和吸附氧,同时进一步引发表面态能级。TiO2纳米粒子PL光谱的产生与其表面氧空位和缺陷有很大关系,并能够提供氧空位和缺陷浓度以及光生电子和空穴的分离与复合等信息。此外,在光催化氧化苯酚的实验中,600℃焙烧的TiO2纳米粒子表现出最高的光催化活性,这与表征结果一致,说明TiO2纳米粒子的性质如晶型结构和表面组成等是影响其活性的主要因素。

TiO2 nanoparticles were prepared by a sol-gel process using Ti(OC4H9)4 as raw material, and also were characterized by XRD, TEM, SPS, XPS, UV-VIS and PL testing techniques. Their properties such as crystallite sizes, crystal structure, surface composition, photoelectricity and optical performance were investigated, and the effects of calcining temperature on the properties of TiO2 nanoparticles were discussed. The results showed that TiO2 nanoparticles experienced the phase transformation process from anatase to rutile as the calcining temperature increased, and exhibits the quantum size effect. TiO2 nanoparticles calcined at 600 ℃ has similar composition, structure, morphology and particle size with international P-25 TiO2 samples, and there was a certain amount of oxygen vacancies on their surface, which was responsible for the existence of a certain amount of hydroxyl and adsorption oxygen, resulting into the surface state energy levels. PL spectra of TiO2 nanoparticles mainly resulted from surface oxygen vacancies and surface defects, providing the information of the seperation and recombination of photoinduced electrons and holes as well as the concentration of vacancies and defects. Moreover, in the experiment of photocatalytic oxidation phenol, TiO2 nanoparticles calcined at 600℃ exhibited the highest photocatalytic activity, which was in good agreement with the characterization results, indicating that the properties such as crystal structure and surface compositions were principal factors influencing the activity of photocatalyst.