中国科学院海洋研究所机构知识库

    光电化学、光致阴极保护和光催化技术的基本原理是将光能转化为电能或者化学能，作为一种高效、环保、节能的绿色技术，在当前各领域交叉融合的高峰期具有非常大的研究价值和应用潜力，备受研究者青睐。作为其重要的一部分，半导体材料的开发和设计成为科研学者研究的重点。多相异质结可以有效提升半导体材料的性能，这主要归因于拓展的光谱吸收、光生电子-空穴对的有效分离和光生载流子的快速传输等。本文以常见的过渡金属Ⅵ族化合物为主，通过建立有效多相异质结体系，并进一步探究其显著改善的光致阴极保护和光催化性能，深入分析其反应机制。另外，本文对部分Cd基硫化物进行相关的改性，并探究其光催化和光电化学性能，为开发和设计高效的多相异质结体系并进一步应用于光致阴极保护领域打下基础。具体研究内容如下：

    1. 构建了一种新型的TiO₂/MgTi_xO_y多相异质结薄膜用于探究对304不锈钢的光致阴极保护性能。物理表征结果表明，MgTi_xO_y成功包覆在TiO₂纳米管阵列的管口表面与其形成多相异质结。并首次利用了扫描开尔文探针测试制备光电极的表面电位分布和功函，较低的表面功函数使得TiO₂/MgTi_xO_y薄膜更容易逸出电子，使得光生载流子的浓度增大。进一步的光致阴极保护性能表明，TiO₂/MgTi_xO_y多相异质结薄膜相比于TiO₂薄膜具有显著增强的光致阴极保护性能，并且其具有极高的稳定性。多相异质结的建立有效抑制了光生电子和空穴的重组，加速了光生载流子的分离。因此，TiO₂/MgTi_xO_y多相异质结薄膜具有显著增强的光致阴极保护性能，同时具有极高的稳定性。

    2. TiO₂/MgTi_xO_y多相异质结薄膜具有显著增强的光致阴极保护性能和长效的稳定性，然而其产生的多余的光生电子难以保证光电极在暗态下对金属的持续保护。本论文进一步通过溶剂热法制备一种新颖的三维分级结构WO₃光电极，并通过电化学方法在其表面沉积ZnO，通过进一步的退火处理，成功制备了WO₃/ZnWO₄/ZnO多相异质结光电极，并进一步探究其光致阴极保护性能。结果表明，多相异质结体系的建立，形成了良好的能带梯度，加速了光生载流子的分离效率，利于光生电子的定向传输并转移出光电极，使得WO₃/ZnWO₄/ZnO的光致阴极保护性能相比于WO₃和ZnO有了显著的提高。同时，由于多相异质结体系中W⁶⁺和W⁵⁺的共存，使得WO₃/ZnWO₄/ZnO光电极具有一定的储存电子能力，可以实现长久有效的光致阴极保护。

    3. Z-型光催化体系可以保证半导体材料较负的导带电位参与光催化反应，本文设计合成一种碳纳米管（CNTs）作为g-C₃N₄/CdZnS中间电子传输体的Z型异质结光催化剂（g-C₃N₄/CNTs/CdZnS）并探究其光催化产氢性能。研究表明，g-C₃N₄/CNTs/CdZnS的光催化产氢性能相比于单相的g-C₃N₄、CdZnS和双相的g-C₃N₄/CdZnS光催化剂得到显著地增强，并且具有很好的光催化稳定性。g-C₃N₄/CNTs/CdZnS增强的光催化产氢性能归因于CNTs作为中间电子介质，能够加速g-C₃N₄价带的光生空穴和CdZnS导带上光生电子的复合，使得Z型光催化剂的表面更容易逸出光生电子、光生载流子的寿命得到延长。这类新型光催化体系可为长效的光致阴极保护体系的开发和设计提供理论基础。

    4. 对部分Cd基硫化物（CdS等）进行相关的改性，并探究其增强的光催化和光电化学性能，为进一步开发和设计高效的多相异质结体系打下基础。其一，通过制备镁掺杂CdS纳米棒（MgCdS），研究了其能带结构和光催化降解性能。结果表明，镁的掺杂拓宽了CdS纳米棒的带隙宽度，使得其光生电子和空穴的复合速率得到有效抑制，从而使得其光催化性能得到提高。其二，通过溶剂热法制备了一种新颖的三维海绵状CdS薄膜光电极，并研究其光电化学性能。光电化学性能测试结果表明，具有微孔海绵结构的CdS薄膜光电极具有优异的光电化学性能和光致阴极保护性能，同时具有很高的稳定性。其三，制备一种新颖的三维纳米花状Co₉S₈分级结构，并进一步在其表面沉积CdS纳米颗粒，成功构建Co₉S₈/CdS Z型异质结光催化体系。研究表明， CdS纳米颗粒均匀的分布于分级结构Co₉S₈表面形成Z型异质结，并协同分级结构提供大量活性位点的作用，有助于光生载流子快速的溢出，从而加速了Co₉S₈/CdS Z型光催化剂的光催化反应进程。

  The basic principle of photoelectrochemistry, photoinduced cathodic protection and photocatalysis technology is to convert light energy into electrical energy or chemical energy. As a green technology with high efficiency, environment friendly and energy saving, the photoelectric conversion technology shows great potential during the high peak of interdisciplinary research, therefore it is favored by researchers from different areas. As an important part, the development and design of semiconductor materials has attracted the focus of scientific researchers. Multiphase heterojunction can effectively improve the performance of semiconductor materials, which is mainly due to the extended spectral absorption, the effective separation of photogenerated electron-hole pairs and the rapid transmission of photogenerated charge carriers. This paper focuses on the establishment of effective heterogeneous heterojunction system based on the common transition metal VI-group compounds, and further explores the methods and mechanism to effectively improve the photoinduced cathodic protection and photocatalytic performance. In addition, this paper also carried out the modification of Cd-based sulfides and their photocatalytic and photoelectrochemical properties, which laid a foundation for the further development and design of efficient heterogeneous heterojunction system for photoinduced cathodic protection. The detailed research contents are as follows.

  1. A novel TiO₂/MgTi_xO_y multiphase heterojunction film was constructed to explore the photoinduced cathodic protection performance for 304 stainless steel. Physical characterization results show that MgTi_xO_y was successfully coated on the nozzle surface of TiO₂ nanotube array and a heterogeneous heterojunction system was formed. The scanning Kelvin probe technique was performed to test the surface potential distribution and work function of the prepared photoelectrode for the first time. The lower surface work function of the TiO₂/MgTi_xO_y film indicates the electrons are easier to escape, which increases the concentration of photogenerated charge carriers. Further photoinduced cathodic protection test results show that the photoinduced cathodic protection performance and stability of TiO₂/MgTi_xO_y multiphase heterojunction film is significantly enhanced compared with those of TiO₂ film. The establishment of multiphase heterojunction effectively inhibits the recombination of photogenerated charge carriers and accelerates their separation. Therefore, the TiO₂/MgTi_xO_y multiphase heterojunction film shows significantly enhanced photoinduced cathodic protection and stability.

  2. TiO₂/MgTi_xO_y multiphase heterojunction films have significantly enhanced photoinduced cathodic protection performance and long-term stability. However, the excess photogenerated electrons generated by TiO₂/MgTi_xO_y heterojunction films are difficult to ensure the continuous protection of the metal by the photoelectrode in the dark state. A novel three-dimensional hierarchical structure WO₃ photoelectrode was prepared by solvothermal method, and ZnO was deposited on its surface by electrochemical method. Through further annealing, WO₃/ZnWO₄/ZnO multiphase heterojunction photoelectrode was successfully prepared, and its photoinduced cathodic protection performance was further explored. The results show that the establishment of multiphase heterojunction system forms a good energy band gradient, which accelerates the separation efficiency of photogenerated charge carriers and promotes the directional transmission of photogenerated electrons. Therefore, the photoinduced cathodic protection performance of WO₃/ZnWO₄/ZnO is significantly improved compared with those of WO₃ and ZnO. At the same time, due to the coexistence of W⁶⁺ and W⁵⁺ in the multiphase heterojunction system, WO₃/ZnWO₄/ZnO photoelectrode has a certain electron storage capacity, which endows it with long-term and effective photoinduced cathodic protection.

  3. Z-Scheme photocatalytic system can ensure the negative conduction band potential of semiconductor materials to participate in photocatalytic reaction. A Z-scheme heterojunction photocatalyst, g-C₃N₄/CNTs/CdZnS with carbon nanotubes (CNTs) as intermediate electron transporter between g-C₃N₄ and CdZnS, was designed, and its photocatalytic hydrogen production performance was investigated. The results show that the photocatalytic hydrogen production performance and stablity of g-C₃N₄/CNTs/CdZnS is significantly enhanced compared with those of single-phase g-C₃N₄, CdZnS and two-phase g-C₃N₄/CdZnS photocatalysts. The enhanced photocatalytic hydrogen production performance of g-C₃N₄/CNTs/CdZnS is attributed to the fact that CNTs, as an intermediate electron medium, can accelerate the recombination of the photogenerated holes in the valence band of g-C₃N₄ with the photogenerated electrons in the conduction band of CdZnS, which makes it easier for photogenerated electrons to escape from the surface of Z-scheme photocatalyst, makes the concentration of photogenerated carriers charge stronger, and prolongs the life of the photogenerated charge carriers. This novel photocatalytic system can provide a theoretical basis for the development and design of long-term photoinduced cathodic protection system.

  4. Some Cd-based sulfides, such as CdS, was modified and explored to enhance the photocatalytic and photoelectrochemical properties, which will lay a foundation for the further development and design of efficient heterogeneous heterojunction system. Firstly, the energy band structure and photocatalytic degradation properties of Mg doped CdS nanorods (MgCdS) was studied. The results show that the doping of Mg element widens the band gap width of CdS nanorods, effectively inhibits the recombination of photogenerated electrons and holes, and improves its photocatalytic performance. Secondly, a novel three-dimensional spongy CdS thin film photoelectrode was prepared by solvothermal method, and its photoelectrochemical properties were studied. The results show that the CdS thin film photoelectrode with microporous sponge structure has excellent photoelectrochemical properties and photoinduced cathodic protection performance, and the stability is also greatly improved. Microporous sponge structure can significantly improve the utilization and conversion efficiency to simulated sunlight, so as to improve its photoelectrochemical properties. Thirdly, a novel three-dimensional nano flower like Co₉S₈ hierarchical structure was prepared with CdS nanoparticles further deposited on its surface, and Co₉S₈/CdS Z-scheme heterojunction photocatalytic system was successfully constructed. The results show that the photocatalytic performance of the hierarchical Co₉S₈/CdS heterojunction photocatalyst is significantly improved. The CdS nanoparticles evenly distribute on the surface of the hierarchical Co₉S₈ to form Z-scheme heterojunction, and cooperate with the hierarchical structure to provide a large number of active sites, which is conducive to the rapid transfer of photogenerated charge carriers, thus accelerating the photocatalytic reaction process of Co₉S₈/CdS Z-scheme photocatalyst.

第1章 绪论... 1

1.1 引言... 1

1.2异质结光电极体系在光致阴极保护领域的研究进展... 2

1.2.1 光致阴极保护的原理及优势... 2

1.2.2 双相异质结光电极的光致阴极保护概述... 3

1.2.3 多相异质结光电极的光致阴极保护概述... 9

1.3异质结体系在光催化领域中的设计和研究进展... 12

1.3.1半导体-半导体异质结体系... 13

1.3.2半导体-金属异质结体系... 16

1.3.3半导体-碳基异质结体系... 19

1.3.4多相异质结体系... 21

1.4 选题意义与研究内容... 25

1.4.1 选题背景与意义... 25

1.4.2 研究内容... 27

第2章 TiO₂/MgTi_xO_y多相异质结薄膜增强光致阴极保护性能... 28

2.1 前言... 28

2.2 实验部分... 29

2.2.1 材料与试剂... 29

2.2.2 仪器与设备... 29

2.2.3 不同光电极的制备... 30

2.2.4不同光电极的物理表征... 31

2.2.5 不同光电极的电化学性能，光致阴极保护性能和SKP测试... 31

2.3 结果与讨论... 32

2.4 本章小结... 42

第3章 WO₃/ZnWO₄/ZnO多相异质结光电极薄膜增强光致阴极保护性能    43

3.1 前言... 43

3.2 实验部分... 44

3.2.1 材料与试剂... 44

3.2.2 仪器与设备... 45

3.2.3 不同光电极的制备... 45

3.2.4 物理表征... 46

3.2.5电化学和光致阴极保护性能测试... 47

3.3 结果与讨论... 47

3.4 本章小结... 59

第4章 g-C₃N₄/CNTs/CdZnS Z型多相异质结光催化剂的制备及其光催化产氢机制研究    60

4.1 前言... 60

4.2 实验部分... 62

4.2.1 材料与试剂... 62

4.2.2 仪器与设备... 62

4.2.3 不同光催化剂的制备... 62

4.2.4不同光催化剂的物理表征... 63

4.2.5 制备的系列光催化剂的光催化产氢性能测试... 63

4.3 结果与讨论... 63

4.4 本章小结... 73

第5章 Cd基硫化物的改性及其光催化和光电化学机制研究... 74

5.1 前言... 74

5.2 镁掺杂CdS的光催化性能及机制研究... 75

5.2.1 实验部分... 75

5.2.1.1 镁掺杂CdS纳米棒的制备... 75

5.2.1.2 仪器、物理表征与测试... 75

5.2.1.3 第一性原理计算方法... 76

5.2.2 结果与讨论... 76

5.2.3 小结... 81

5.3 三维海绵状CdS薄膜的制备及其光电化学性能研究... 81

5.3.1 实验部分... 82

5.3.1.1 CdS薄膜光电极的制备... 82

5.3.1.2 仪器、物理表征与光电化学测试... 83

5.3.2 结果与讨论... 83

5.3.3 小结... 88

5.4分级结构Co₉S₈/CdS Z-型异质结光催化剂光催化性能及反应机制研究... 88

5.4.1 实验部分... 89

5.4.1.1 系列光催化剂的制备... 89

5.4.1.2 仪器、物理表征与光电化学测试... 89

5.4.2 结果与讨论... 89

5.4.3 小结... 94

5.5 本章小结... 95

第6章 结论与展望... 97

6.1 结论... 97

6.2 创新点... 99

6.3 展望... 99

参考文献... 102

致  谢... 121

作者简历及攻读学位期间发表的学术论文与研究成果... 123