物理化学学报 >> 2019, Vol. 35 >> Issue (8): 885-895.doi: 10.3866/PKU.WHXB201812022

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缺陷TiO2-x中空微球的制备及光催化降解亚甲基蓝性能

章家伟1,王晟1,*(),刘福生2,*(),付小杰1,马国权2,侯美顺1,唐卓1   

  1. 1 南京工业大学化工学院,南京 210009
    2 南京林业大学理学院化学与材料科学系,南京 210037
  • 收稿日期:2018-12-11 录用日期:2019-01-25 发布日期:2019-02-15
  • 通讯作者: 王晟,刘福生 E-mail:W_angsheng@njtech.edu.cn; w_angshengnj@163.com;lfs039270@163.com
  • 基金资助:
    国家自然科学基金(50876047);国家自然科学基金(TAPP, PPZY2015A044)

Preparation of Defective TiO2-x Hollow Microspheres for Photocatalytic Degradation of Methylene Blue

Jiawei ZHANG1,Sheng WANG1,*(),Fusheng LIU2,*(),Xiaojie FU1,Guoquan MA2,Meishun HOU1,Zhuo TANG1   

  1. 1 College of Chemical Engineering, Nanjing Tech University, Nanjing 210009, P. R. China
    2 Department of Chemistry and Materials Science, College of Science, Nanjing Forestry University, Nanjing 210037, P. R. China
  • Received:2018-12-11 Accepted:2019-01-25 Published:2019-02-15
  • Contact: Sheng WANG,Fusheng LIU E-mail:W_angsheng@njtech.edu.cn; w_angshengnj@163.com;lfs039270@163.com
  • Supported by:
    the National Natural Science Foundation of China(50876047);Top-notch Academic Programs Project of Jiangsu Higher Education Institutions, China(TAPP, PPZY2015A044)

摘要:

通过氢还原TiO2中空微球制备有缺陷的TiO2-x中空微球。采用冷场发射扫描电子显微镜(SEM)、透射电镜(TEM)、X射线衍射法(XRD)、X射线光电子能谱(XPS)、电子顺磁共振波谱(ESR),拉曼光谱仪、紫外-可见漫反射光谱(UV-Vis DRS)和电化学测试等对制得的光催化剂进行了结构和性能表征。采用可见光催化降解亚甲蓝(MB)性能对光催化剂的光催化活性进行评价。分析了提高光催化活性的机理及MB的降解机理。在探讨MB初始浓度对降解过程的影响的基础上提出了一种新的光催化降解染料动力学模型。结果表明TiO2-x中空微球的光催化活性优于TiO2-x是因为形成了具有更高比表面积的中空微球结构。降解MB分子的氧化剂为h+、•O2-和•OH,其中仅由光生空穴生成的•OH起了主要作用。与拟一级动力学模型相比,新的模型可以更真实有效地描述光催化降解MB过程,因为不仅其计算结果更符合实验数据,而且该模型中的速率常数不随染料初始浓度的变化而变化。

关键词: 中空微球TiO2, 氧空位, 光催化, 降解, 动力学

Abstract:

In recent years, photocatalytic degradation of organic pollutants has attracted considerable attention because of its potential application for solving environmental problems. Among various semiconductor photocatalysts, TiO2 is considered a promising candidate due to its excellent structural stability. Many researchers have focused on improving the visible-light catalytic efficiency of TiO2, because the large band gap of TiO2 limits its utilization of visible light energy. Recently, it has been proved that intrinsic defects like oxygen vacancies in TiO2 can trigger the visible light activity. TiO2 hollow microspheres with large surface areas have shown high photocatalytic efficiencies in the degradation of organic pollutants. To date, the photocatalytic performance of TiO2-x hollow microspheres has not been investigated. The kinetics of photocatalytic degradation of organic dyes is usually depicted by the pseudo-first-order kinetic equation. However, a few studies have demonstrated the impact of light absorption by the dye itself on photocatalytic performance in terms of the rate equation. In this study, defective TiO2-x hollow microspheres were prepared by the hydrogen reduction process to effectively promote photocatalytic activity under visible light irradiation. The structure and properties were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), electron spin-resonance (ESR), Raman spectrometry, ultraviolet-visible diffuse-reflectance spectroscopy (UV-Vis DRS), and electrochemical tests. The photocatalytic performance was evaluated based on the photocatalytic degradation of methylene blue (MB) solution under visible light irradiation. The mechanism underlying the enhancement of photocatalytic activity was also discussed. The results show that the visible-light photocatalytic activity of TiO2-x, and TiO2-x hollow microsphere benefit from the presence of oxygen vacancies on the surface. The photocatalytic activity of TiO2-x hollow microspheres is better than that of TiO2-x, attributed to the formation of hollow structures with higher specific surface areas. The mechanism of MB degradation occurring on the TiO2-x hollow microsphere surface was also investigated. The results show that the MB molecules are photodegraded by the photogenerated hole (h+), reactive superoxide radical (•O2-), and hydroxyl radicals (•OH), and that the •OH radicals, produced only by photogenerated holes, play an essential role in the degradation of MB. Based on the discussion of the effect of initial concentration of MB on the degradation process, a new kinetic model was proposed for the photocatalytic degradation of dye, considering the effect of visible light absorbed by MB molecules, because the data estimated by pseudo-first-order kinetic equation do not fit well with the experimental data. The Runge-Kutta method was used to obtain the numerical solution of the kinetic model. The results show that the kinetic model proposed for photocatalytic dye degradation gives a more realistic description of the photocatalytic degradation of MB because the calculated results fit better with the experimental data. The rate constant (kapp) of the pseudo-first-order kinetic equation decreases with increasing initial concentration of MB, indicating that kapp is affected by the light absorption properties of MB, because an increase in the initial concentration of MB will lead to increased absorption of visible light by MB molecules rather than by TiO2-x hollow microsphere. Unlike the rate constant kapp, the rate constant ka in the proposed model describes the process of photocatalytic dye degradation more effectively because it does not depend on the initial dye concentration.

Key words: TiO2 hollow microsphere, Oxygen vacancy, Photocatalysis, Degradation