学位论文 > 优秀研究生学位论文题录展示

活性物种在液相光催化降解有机污染物过程中的作用本质研究

作　者: 李文娟
导　师: 李旦振
学　校: 福州大学
专　业: 材料化学
关键词: 光催化 TiO2 ZnxCd1-xS ZnO 活性物种
分类号: O643.3
类　型: 博士论文
年　份: 2011年
下　载: 10次
引　用: 0次
阅　读: 论文下载
 

内容摘要


半导体光催化技术在环境污染治理领域的应用已成为近年来国内外研究的热点。液相光催化机理的研究主要集中在引发光催化过程的活性物种方面，但对于它们在光催化过程中具体的作用机制仍未清楚。因此，系统地阐明不同体系的光催化过程对于认识光催化机理及制备可见光催化剂都有极大的指导意义。本文首先以TiO2降解甲基橙（MO）过程为例，研究此过程中的主要活性物种及各自的作用。然后通过对比ZnxCd1-xS与TiO2降解MO过程中的主要活性物种及其作用，揭示可见光与紫外光体系中，活性物种的不同特点。继而又研究在同一紫外光体系下，ZnO与TiO2降解MO过程中的活性物种及它们的来源。最后，研制出一种能显著增强光敏化作用从而达到进一步降解污染物的新型ZnxCd1-xS/TiO2类的光催化剂。运用X射线衍射（XRD）、紫外－可见漫反射光谱（UV-vis DRS）、X射线光电子能谱（XPS）、透射电镜（TEM）等对催化剂的组成、结构和形貌进行表征。采用电子自旋共振（ESR）、核磁共振（NMR）、荧光光谱（PL）、电化学分析、液相色谱-质谱联用（LCMS）等技术对催化过程中的活性物种及降解中间产物进行检测和研究，主要结果如下：（1） TiO2降解MO过程中的主要活性物种是O2，空穴和OH次之。溶解氧和表面OH对这些物种的产生起重要作用；（2）采用水热和微波溶剂热法合成ZnxCd1-xS纳米晶，与TiO2对比发现，在Zn0.28Cd0.72S可见光降解MO体系中, O2和空穴起主要作用；在Zn0.28Cd0.72S紫外光和TiO2紫外光降解体系中, O2, OH和空穴起主要作用；（3） ZnO和TiO2在液相降解过程中表现出不同的性质。在TiO2体系中， OH是由空穴产生；在ZnO体系中， OH是由空穴和O2共同产生；（4）通过简单的水热法合成出ZnxCd1-xS/TiO2复合物，实验证明这两种半导体的复合极大地增强了可见光光敏化降解罗丹明B（RhB）的作用，染料与催化剂之间的电子转移起重要作用。论文的特色与创新：（1）利用电化学分析及各种表征手段揭示出TiO2降解MO体系中活性物种与光催化过程的关系；（2） ZnxCd1-xS纳米晶首次被应用于光催化降解染料，并显示出较好的光催化活性；（3）首次对比并揭示出Zn0.28Cd0.72S和TiO2降解MO过程中主要活性物种的作用；（4）发现ZnO和TiO2降解MO过程中活性物种的来源不同；（5）利用半导体复合的方法增强了光敏化作用，首次制备出活性较好的ZnxCd1-xS/TiO2复合型催化剂。

全文目录


中文摘要  5-6
Abstract  6-8
Contents  8-13
1 Preface  13-46
  1.1 Semiconductor Photocatalysis Review  13-18
    1.1.1 Background of Photocatalysis  13
    1.1.2 Mechanism of Photocatalysis  13-15
    1.1.3 Application of Semiconductor Photocatalysis  15-18
      1.1.3.1 Wastewater Treatment  16
      1.1.3.2 Indoor Air Purification  16-17
      1.1.3.3 Anti-bacterial and Deodorizing  17
      1.1.3.4 Self-cleaning  17-18
      1.1.3.5 Hydrogen Production  18
  1.2 Investigation of the Active Species in Degradation of Organic Pollutants by Aqueous-Phase Photocatalysis  18-36
    1.2.1 The Role of the Active Species in the Photocatalytic Process  18-27
      1.2.1.1 Photogenerated Electrons  18-19
      1.2.1.2 Photogenerated Holes  19
      1.2.1.3 Hydroxyl Radicals ( OH)  19-20
      1.2.1.4 Superoxide Radicals (O_2 )  20-21
      1.2.1.5 Dissolved Oxygen  21-22
      1.2.1.6 Hydrogen Peroxide  22-23
      1.2.1.7 The Combined Action of OH, O_2 and Excited Holes (h+)  23-24
      1.2.1.8 Hydrated Electrons (eaq-) and H  24-27
    1.2.2 The Detection Techniques of the Active Species  27-32
      1.2.2.1 Electron Spin Resonance (ESR) Technique  27
      1.2.2.2 Terephthalic Acid (TA)–Fluorescence (FL) Probe Method  27-28
      1.2.2.3 Luminol Chemiluminescence (CL) Probe Method  28
      1.2.2.4 The Transient Grating (TG) Technique  28-30
      1.2.2.5 X-ray Absorption Near-edge Structural (XANES)  30
      1.2.2.6 Single-molecule Fluorescence Imaging Technique  30
      1.2.2.7 Different Types of Scavengers  30-32
        1.2.2.7.1 Scavengers for OH Radicals  30-31
        1.2.2.7.2 Scavengers for Holes  31
        1.2.2.7.3 Scavengers for Electrons  31-32
        1.2.2.7.4 Scavengers for O_2 Radicals  32
        1.2.2.7.5 Scavengers for eaq-and H  32
    1.2.3 Sources of the Active Species  32-35
      1.2.3.1 Sources of OH Radicals  32-34
      1.2.3.2 Sources of O_2 Radicals  34
      1.2.3.3 Sources of eaq  34-35
    1.2.4 Present Questions  35-36
  1.3 Design of Photocatalysts with High Activity  36-43
    1.3.1 Modification for Photocatalysts  36-41
      1.3.1.1 Effect of Crystal Form  36-37
      1.3.1.2 Effect of Particle Size  37
      1.3.1.3 Composite of the Semiconductors  37-38
      1.3.1.4 Metal and Nonmetal Ion Dopants  38-40
      1.3.1.5 Surface Sensitization  40-41
    1.3.2 Synthesis Method  41-43
      1.3.2.1 Hydrothermal Synthesis  41
      1.3.2.2 Microwave-assisted Hydrothermal Synthesis  41-42
      1.3.2.3 Precipitation Method  42-43
      1.3.2.4 Other Methods  43
  1.4 Foundation of Dissertation and Research Scheme  43-46
2 Experimental  46-59
  2.1 Reagents and Apparatus  46-48
    2.1.1 Reagents  46
    2.1.2 Apparatus  46-48
  2.2 Experimental Section  48-55
    2.2.1 Preparation of Photocatalysts  48-50
      2.2.1.1 Hydrothermal Synthesis of Zn_xCd_(1-x)S Nanoparticles  48
      2.2.1.2 Microwave Synthesis of Zn_xCd_(1-x)S Nanorods  48-49
      2.2.1.3 One Step Preparation of Zn_xCd_(1-x)S/TiO_2Nanocomposites  49-50
      2.2.1.4 Preparation of Standard TiO_2-xNx  50
    2.2.2 Characterizations of Photocatalysts  50-55
      2.2.2.1 X-ray Diffraction (XRD)  50
      2.2.2.2 N2Adsorption (BET)  50-51
      2.2.2.3 UV-vis Diffuse Reflectance Spectroscopy (DRS)  51
      2.2.2.4 Transmission Electron Microscopy (TEM)  51-52
      2.2.2.5 Liquid Chromatography Mass Spectroscopy (LCMS)  52
      2.2.2.6 X-ray Photoelectron Spectroscopy (XPS)  52
      2.2.2.7 Total Organic Carbon (TOC)  52-53
      2.2.2.8 Photoluminescence Technique using Terephthalic Acid (PL-TA)  53
      2.2.2.9 Electron Spin Resonance (ESR) Technique  53-54
      2.2.2.10 Fourier Transform Infrared Spectroscopy (FTIR)  54
      2.2.2.11 1H Magnetic-angle Spinning (MAS) NMR Spectroscopy  54
      2.2.2.12 Tests of Electrochemical Parameters  54
      2.2.2.13 Determination of the Flat Band Potential (Vfb)  54-55
  2.3 Aqueous-phase Photocatalytic Activity Measurements  55-59
    2.3.1 Aqueous-phase Photocatalytic Activity Tests (Visible Light)  56-57
    2.3.2 Aqueous-phase Photocatalytic Activity Tests (UV Light)  57-58
    2.3.3 Detection of the Surface Density of Hydroxyl Groups on the Surface of TiO_2  58-59
3 Role of Main Active Species in Degradation of Methyl Orange on TiO_2 Photocatalyst  59-85
  3.1 Introduction  59-60
  3.2 Role of Surface Hydroxyl Groups in the Aqueous-phase Photocatalytic Activity of TiO_2  60-73
    3.2.1 Experimental Detection of Surface Hydroxyl Groups  60-66
    3.2.2 Relationship between Hydroxyl Groups and OH Radicals  66-68
    3.2.3 The Role of Hydroxyl Groups in the Photocatalytic Activity  68-73
  3.3 Detection of the Active Species by Scavengers  73-76
  3.4 The Generation of O_2 and OH Radicals during TiO_2Photocatalysis  76-77
  3.5 The relationship between the active species and the degradation process  77-84
  3.6 Brief Summary  84-85
4 Specific Analysis of the Active Species on Zn_xCd_(1-x)S and TiO_2Photocatalysts in the Degradation of Dyes  85-126
  4.1 Introduction  85-86
  4.2 Preparation of Zn_xCd_(1-x)S Nanoparticles and Their Photocatalytic Performance under Visible Light Irradiation  86-97
    4.2.1 XRD, TEM and DRS Investigations  86-89
    4.2.2 Photocatalytic Activity Investigations  89-92
    4.2.3 Stability Investigations (XRD, TEM and XPS)  92-94
    4.2.4 Degradation of Other Dyes  94-96
    4.2.5 Discussion of the Degradation Mechanism  96-97
  4.3 Microwave Synthesis of Zn_xCd_(1-x)S Nanorods and Their Photocatalytic Activity under Visible Light Irradiation  97-109
    4.3.1 XRD, TEM, BET and DRS Investigations  97-101
    4.3.2 Photocatalytic Activity Investigations  101-105
    4.3.3 Exploration of the Degradation Mechanism  105-109
  4.4 Comparison of the Active Species on Zn_(0.28)Cd_(0.72)S and TiO_2Photocatalysts in the Degradation of Methyl Orange  109-124
    4.4.1 Comparison of the Degradation Processes  109-114
    4.4.2 Comparison of the Active Species during Zn_(0.28)Cd_(0.72)S and TiO_2 Photocatalysis  114-123
      4.4.2.1 Detection of the Active Species by Scavengers  114-116
      4.4.2.2 The Generation of OH Radicals  116-119
      4.4.2.3 The Generation of O_2 Radicals and H2O_2  119-121
      4.4.2.4 The Sources of OH Radicals  121-123
    4.4.3 Comparison of the Degradation Mechanisms  123-124
  4.5 Brief Summary  124-126
5 New Perspective on the Active Species in the Degradation of Methyl Orange over ZnO and TiO_2Photocatalysts  126-139
  5.1 Introduction  126-127
  5.2 Comparison of the Degradation Processes  127-128
  5.3 Comparison of the Active Species during TiO_2and ZnO Photocatalysis  128-137
    5.3.1 Detection of the Active Species by Scavengers  128-130
    5.3.2 Comparison of the Hydroxyl Groups on the Surface of TiO_2and ZnO  130-132
    5.3.3 The Generation of OH Radicals  132-133
    5.3.4 The Generation of O_2 -and Role of DO  133-136
    5.3.5 The Sources of OH Radicals  136-137
  5.4 Brief Summary  137-139
6 Novel Approach to Enhance Photosensitized Degradation of Rhodamine B under Visible Light Irradiation by the Zn_xCd_(1-x)S/TiO_2Nanocomposites  139-156
  6.1 Introduction  139-140
  6.2 Physicochemical Properties of ZCT Composites  140-144
  6.3 Photocatalytic Activity of ZCT Nanocomposites  144-148
  6.4 Mechanism of the Degradation Process  148-155
  6.5 Brief Summary  155-156
7 Conclusions and Prospects for Future Works  156-159
  7.1 Main Conclusions of this Dissertation  156-158
  7.2 Prospects for Future Research  158-159
References  159-181
Acknowledgements  181-182
Personal Resume  182-183
List of Publications  183-185

相似论文

  1. 钛酸盐光催化剂的制备及光催化分解水性能,O643.36
  2. 基于酚醛树脂活性炭的制备及负载TiO2吸附—光催化性能,TQ424.19
  3. 可磁分离的TiO2基光催化纳米纤维的制备研究,TB383.1
  4. Fe，V共掺杂TiO2催化剂的合成、表征及其性能研究,O614.411
  5. 静电纺丝法制备TiO2及其光催化行为的研究,O614.411
  6. 化学吸附法脱除FCC汽油中含硫化合物的研究,TE624.55
  7. 掺杂锐钛矿型二氧化钛光催化性能的第一性原理计算,O643.36
  8. 功能化纳米二氧化钛多孔材料的制备、表征及性能研究,TB383.1
  9. 生物催化/光催化联合降解毒死蜱的研究,X592
  10. 铁、镧掺杂纳米TiO2的制备及光催化性能研究,O614.411
  11. 基于绿色化学理念的纳米硫化镉的合成及应用,O614.242
  12. 半导体光催化材料的制备及其光催化性能研究,O643.36
  13. 微囊藻毒素的降解与消除方法研究,X173
  14. 多孔氧化铜空心微球的制备及表征,O614.121
  15. 纳米LaFeO3的可控合成及其与TiO2桥联复合光催化剂建构,O643.36
  16. 基于微乳液体系制备ZnO光催化材料,O614.241
  17. 晶相可控的纳米TiO2制备及性能研究,TB383.1
  18. 水热及微波水热法合成超细纳米TiO2的研究,TB383.1
  19. 中空球型纳米Bi2WO6的制备及光催化降解水中有机污染物的研究,X703.1
  20. ZnO-TiO2复合体的改性及其光催化性能研究,X703
  21. 修饰对TiO2表面光伏特性的影响及其机制研究,O614.411

中图分类: > 数理科学和化学 > 化学 > 物理化学（理论化学）、化学物理学 > 化学动力学、催化作用 > 催化
© 2012 www.xueweilunwen.com