TiO_2纳米颗粒的制备、光催化性能及羟基自由基研究

Preparation,Photocatalytic Properties and Photogenerated Hydroxyl Radicals of TiO_2 Nanoparticles

采用聚丙烯酰胺凝胶法制备了TiO2纳米颗粒,利用X射线衍射、扫描电子显微镜和紫外-可见光漫反射光谱分别研究了不同煅烧温度对样品晶相、颗粒形貌和带隙的影响.以甲基橙(MO)为目标降解物,在紫外光照射下考察了制得的TiO2样品的光催化性能.研究结果表明,500℃煅烧制备的样品光催化性能最好;随着催化剂用量的增加,MO降解率呈现先增大后减小的趋势,最佳催化剂用量为4.0 g/L;在pH值不太高时(≤7.2),MO降解率随pH值的升高呈下降趋势.以香豆素为探测剂,采用荧光光谱检测催化剂在紫外光照射下产生羟基自由基(.OH)的情况,研究了煅烧温度、催化剂用量和溶液pH值对.OH产率的影响.研究结果还表明,.OH产率与MO降解率的变化规律基本一致,表明.OH可能是TiO2光催化降解有机染料的主要活性物种.

A polyacrylamide gel route was used to prepare TiO2 nanoparticles. X-ray diffraction（XRD）, scanning electron microscope （SEM） and ultraviolet-visible diffuse reflectance spectrometer （UV-Vis DRS） were used to investigate the influences of calcining temperature on the crystalline phase, particle morphology and bandgap energy of products. The photocatalytic properties of the prepared TiO2 samples were investigated by the degradation of methyl orange （MO） under UV irradiation. The results reveal that the sample prepared at 500 ℃ exhibits the highest photocatalytie activity. With the increase of cat- alyst loading, the degradation rate of MO increases firstly and then decreases, with the optimal catalyst loading being 4.0 g/L. When the pH level is not very high（≤7.2）, the MO degradation rate exhibits a decreasing trend with the increase of pH level. Hydroxyl radicals（.OH） formed on the catalyst under UV irradiation were detected by the photoluminescence （PL） spectroscopy using coumarin as a probe molecule, and the effects of calcining temperature, catalyst loading and pH value on the yield of · OH were investigated. The results reveal that similar to the MO degradation rate, · OH yield also depends on the above variables, indicating that the · OH radical is likely to be the main active species respon- sible for dye degradation.