海洋环境腐蚀与生物污损重点实验室知识库

304不锈钢（304SS）具有良好耐蚀性，但当其应用于海洋环境中时，氯离子会破坏其表面钝化膜，促进点蚀的产生。光生阴极保护技术是一种新型绿色的阴极保护防腐方法，常以TiO₂作为光电转换中心。但TiO₂带隙过宽且光生载流子易复合，导致其光电活性较差。针对TiO₂的缺点，本文通过阳极氧化法制备了TiO₂纳米管，设计了Sb₂S₃/Sb₂O₃/TiO₂、Co₃O₄/TiO₂和BiOI/TiO₂三种窄带隙半导体敏化的TiO₂基p-n异质结材料，之后对样品进行了材料表征和光电性能测试，并对其保护机理进行了分析讨论。

通过一锅水热法将Sb₂S₃、Sb₂O₃同时沉积到TiO₂管上，并考察了反应源浓度对复合膜性能的影响。结果发现纳米网状的Sb₂S₃促进了TiO₂对可见光的吸收，微米棒状的Sb₂O₃使载流子沿轴向运动，为载流子传输提供了直接通路；导带较负的Sb₂S₃将TiO₂费米能级拉向更负的电位，利于电子向304SS的传输；p型Sb₂S₃与n型Sb₂O₃/TiO₂内建电场的形成促进了载流子的定向传输。当锑源浓度为48 mmol/L时，三元复合物对304SS保护效果最优，可使其电位降至-0.76 V。

通过低温水热法，制备了Co₃O₄/TiO₂复合物，并研究了Co₃O₄负载量对光生阴极保护效果的影响。结果发现Co₃O₄的引入使TiO₂吸收波长向可见光移动，带隙减小为2.2 eV。当硝酸钴的浓度为1 mmol/L时，Co₃O₄/TiO₂对304SS的保护性能最好，偶合光致电位达到-0.69 V，光电流增加为原来的3倍，电荷转移电阻减小一个数量级。Co₃O₄和TiO₂接触后，由接触前的嵌套式能带结构转变为交错型p-n异质结。在内建电场的驱动下，载流子得到及时分离与定向传输，从而对304SS展现出良好的阴极保护效果。

通过连续去离子层吸附反应，将BiOI原位生长于TiO₂管口，并研究了循环次数对光阳极阴极保护性能的影响。结果发现BiOI的引入使TiO₂吸收边向长波移动，吸收强度显著增大。当循环次数为5次时复合膜保护性能最优，相较TiO₂，复合膜与304SS的偶合光电流变为9倍多，电荷转移电阻减小两个数量级，极大增加了光生载流子分离率。复合膜光阳极可使304SS电位降至-0.66 V，在暗态下仍可对不锈钢实施长达10 h以上的阴极保护。其优异的性能来自于BiOI薄层状结构和交错型p-n内建电场的协同作用。

304 stainless steel (304SS) has good corrosion resistance. However, when the metal is used in marine environment, its passive film could be damaged by chloride ion, thus inducing pitting corrosion. Photocathodic protection technology is a new type of cathodic protection technology, which is a truly green anticorrosion method for metal. Photogenerated cathodic protection is a new green cathodic protection anticorrosive method, which often uses TiO₂ as photoelectric conversion center. Nevertheless, TiO₂ shows poor photoelectric activity due to the wide band gap and easy recombination of photogenerated carriers. Aiming at overcome the shortcomings of TiO₂, in this paper, TiO₂ nanotubes were prepared by anodic oxidation method and then three narrow bandgap semiconductor sensitized TiO₂-based p-n heterojunction materials of Sb₂S₃/Sb₂O₃/TiO₂, Co₃O₄/TiO₂ and BiOI/TiO₂ were designed. Furthermore, the material characterizations and photoelectric properties of the samples were tested, and the protection mechanism was analyzed.

Sb₂S₃ and Sb₂O₃ were simultaneously deposited on titanium dioxide tubes by one-pot hydrothermal method, and the effect of reaction source concentration on photo-induced cathodic protection properties was investigated. The results show that nano-reticulated Sb₂S₃ promotes the visible light absorption of TiO₂, while micron rod-shaped Sb₂O₃ makes carriers move along their axes, providing a direct channel for carrier transport; Sb₂S₃ with negative conduction band pulls the Fermi level of TiO₂ to a more negative potential, therefore, facilitating electron transport to 304SS; the built-in electric fields of p-type Sb₂S₃ and n-type Sb₂O₃/TiO₂ promotes the directional transport of carriers. When antimony source concentration is 48 mmol/L, the ternary composite has the best protective effect on 304SS with a photoinduced coupling potential of -0.76 V.

Co₃O₄/TiO₂ composites were prepared by low-temperature hydrothermal method, and the effect of Co₃O₄ loading amount on protection properties were studied. The results show that after introducing Co₃O₄, the absorption wavelength of TiO₂ shifts to visible light and the band gap reduces to 2.2 eV. When the concentration of cobalt nitrate is 1 mmol/L, the composite film has the best cathodic protection performance for 304SS. In this case, the coupling photovoltaic potential reaches -0.69 V, additionally, the coupling photocurrent increases by three times, and charge transfer resistance decreases by an order of magnitude. After the contact of Co₃O₄ and TiO₂, the previous straddling band structure was transformed into a staggered p-n heterojunction. Under the action of built-in electric field, the timely separation and directional transmission of carriers are driven, which shows good cathodic protection effect for 304SS.

BiOI was grown in situ on the orifice of TiO₂ by successive ionic layer adsorption and reaction method, moreover, the effect of cycle times on the photocathode cathodic protection performance of composite was studied. The results show that with the presence of BiOI, the absorption band edge of TiO₂ is red-shifted and the absorption intensity is significantly increased. The composite film exhibits the best protection performance with five cycle of BiOI. At this situation, compared with titanium dioxide, the photoinduced current density between composite film and 304SS increases more than 9 times, and the charge transfer resistance reduces by two orders of magnitude, which greatly promotes the separation rate of photogenerated carriers. The composite photocathode can reduce the potential of 304SS to -0.66 V, and cathodic protection of 304SS can be carried out for more than 10 hours in dark. Its excellent performance comes from the synergistic effect of BiOI thin layer structure and staggered p-n built-in electric field.

第一章  绪论..................................................................................... 1

1.1  研究背景.......................................................................................................... 1

1.1.1  金属在海洋环境中的腐蚀....................................................................... 1

1.1.2  常用金属腐蚀防护方法........................................................................... 2

1.2  光生阴极保护方法的原理及优点.................................................................. 3

1.3  TiO₂的特性及制备方法................................................................................... 5

1.3.1  TiO₂的特性................................................................................................ 5

1.3.2  TiO₂的制备方法........................................................................................ 6

1.4  改性TiO₂在光生阴极保护应用...................................................................... 7

1.4.1  金属/非金属离子掺杂.............................................................................. 7

1.4.2  贵金属沉积............................................................................................... 8

1.4.3  碳材料复合............................................................................................... 9

1.4.4  聚合物复合............................................................................................... 9

1.4.5  半导体复合............................................................................................. 10

1.5  本论文研究意义与内容................................................................................. 11

1.5.1  选题意义.................................................................................................. 11

1.5.2  研究内容................................................................................................. 12

第二章  实验材料及方法................................................................ 15

2.1  实验药品........................................................................................................ 15

2.2  实验仪器........................................................................................................ 15

2.3  实验材料预处理............................................................................................ 16

2.4  材料表征方法................................................................................................ 17

2.5  电化学表征方法及装置................................................................................ 18

第三章  Sb₂S₃/Sb₂O₃/TiO₂材料及光生阴极保护研究..................... 21

3.1  引言................................................................................................................ 21

3.2  实验................................................................................................................ 22

3.2.1  材料制备................................................................................................. 22

3.2.2  材料表征................................................................................................. 23

3.2.3  材料光电化学测试................................................................................. 23

3.3  结果与讨论.................................................................................................... 24

3.3.1  Sb₂S₃/Sb₂O₃/TiO₂的形貌分析................................................................. 24

3.3.2  Sb₂S₃/Sb₂O₃/TiO₂的组成分析................................................................. 25

3.3.3  Sb₂S₃/Sb₂O₃/TiO₂的光吸收性能分析..................................................... 29

3.3.4  Sb₂S₃/Sb₂O₃/TiO₂的光电化学性能测试................................................. 29

3.3.5  Sb₂S₃/Sb₂O₃/TiO₂对304SS实际保护效果............................................ 32

3.3.6  Sb₂S₃/Sb₂O₃/TiO₂光生阴极保护机理讨论............................................. 33

3.4  本章小结........................................................................................................ 34

第四章  Co₃O₄/TiO₂材料及光生阴极保护研究.............................. 35

4.1  引言................................................................................................................ 35

4.2  实验................................................................................................................ 35

4.2.1  材料制备................................................................................................. 35

4.2.2  材料表征................................................................................................. 36

4.2.3  材料光电化学测试................................................................................. 37

4.3  结果与讨论.................................................................................................... 37

4.3.1  Co₃O₄/TiO₂的形貌分析.......................................................................... 37

4.3.2  Co₃O₄/TiO₂的组成分析.......................................................................... 38

4.3.3  Co₃O₄/TiO₂的光吸收性能分析.............................................................. 41

4.3.4       Co₃O₄/TiO₂对304SS光生阴极保护测试............................................. 42

4.3.5  Co₃O₄/TiO₂的光电化学测试.................................................................. 44

4.3.6  Co₃O₄/TiO₂光生阴极保护机理讨论...................................................... 47

4.4  本章小结........................................................................................................ 49

第五章  BiOI/TiO₂材料及光生阴极保护研究................................ 51

5.1  引言................................................................................................................ 51

5.2  实验................................................................................................................ 52

5.2.1  材料制备................................................................................................. 52

5.2.2  材料表征................................................................................................. 52

5.2.3  材料光电化学测试................................................................................. 53

5.3  结果与讨论.................................................................................................... 53

5.3.1  BiOI/TiO₂的形貌分析............................................................................ 53

5.3.2  BiOI/TiO₂的组成分析............................................................................ 54

5.3.3  BiOI/TiO₂的光吸收性能分析................................................................ 56

5.3.4  BiOI/TiO₂对304SS光生阴极保护性能测试........................................ 57

5.3.5  BiOI/TiO₂的光电性能测试.................................................................... 60

5.3.6  BiOI/TiO₂光生阴极保护机理讨论........................................................ 63

5.4  本章小结........................................................................................................ 65

第六章  结论与展望........................................................................ 67

6.1  结论................................................................................................................ 67

6.2  创新点............................................................................................................ 67

6.3  展望................................................................................................................ 68

参考文献.......................................................................................... 69

致  谢.............................................................................................. 83

作者简历及攻读学位期间发表的学术论文与研究成果.................. 85