N、F共掺杂可见光响应介孔TiO_2光催化剂:纤维素模板剂合成及活性

Mesoporous N-F Codoped TiO_2 Photocatalyst with Visible-Light Response: Preparation Using Cellulose Template and Catalytic Performance

以纤维素为模板剂,TiCl4为钛源,采用液相水解-沉淀法制备了浅黄色的N、F共掺杂可见光响应介孔TiO2催化剂(TiONF)。以苯酚为模型物,考察了TiONF在紫外光区、可见光区及太阳光下催化活性;采用X射线光电子能谱(XPS)、傅里叶变换红外(FTIR)、紫外-可见漫反射光谱(UV-Vis DRS)、X射线衍射(XRD)、热重/量热扫描(TG/DSC)、透射电镜(TEM)及低温N2物理吸附-脱附等技术对TiONF催化剂的结构进行了表征。结果表明,以纤维素为模板剂合成适量N、F共掺杂的TiONF催化剂在紫外光区、可见光区及太阳光下均表现出较高的活性,且高于无模板剂合成的TiONF催化剂的活性。N、F共掺杂提高了TiO2表面羟基数量和锐钛矿相TiO2向金红石相转变的温度;N掺杂形成新的能级结构,诱发TiO2可见光催化活性;F掺杂促进TiO2粒子表面氧空穴产生,致使TiO2粒子表面酸度和Ti3+增加。另外,纤维素的加入可减小TiONF颗粒平均尺寸,改善催化剂分散性,提高催化剂比表面积。

A yellow-colored and mesoporous N-F codoped TiO2 photocatalyst （TiONF） with visible-light response was prepared by a hydrolysis-precipitation method using cellulose as the template and TiClg as the precursor. The photocatalytic activity was evaluated through the photocatalytie degradation of phenol under ultraviolet （UV）, artificial visible （Vis） and solar light irradiation, respectively. The catalysts were characterized by X-ray photoelectron spectroscopy （XPS）, UV-Vis diffuse reflectance spectroscopy （UV-Vis DRS）, X-ray diffraction （XRD）, thermogravimetry-differential scanning calorimetry （TG/DSC）, Fourier transform infrared spectroscopy （FTIR）, transmission electron microscopy （TEM） and N2 adsorption-desorption. The results show that the TiONF obtained by using the cellulose template with suitable N-F doping exhibits higher activity under UV, Vis and solar light irradiation than that obtained without the cellulose template. N-F eodoping can increase the amount of surface OH- of TiO2, and retards phase transformation. N-doping can form a new band-gap to extend the light response of TiO2 to visible region, F-doping can promote generation of oxygen vacancies on the surface of TiO2, and can increase surface acidity and Ti^3＋ of TiO2. The addition of the cellulose template can reduce the average grain size and increase the specific area of TiONF.