海洋环境腐蚀与生物污损重点实验室知识库

本文围绕光生阴极保护这一新兴的金属防腐蚀方法，研究了几种复合半导体材料在可见光下对金属的光生阴极保护性能。TiO₂半导体材料由于其价格低廉、化学性能稳定、光电性能优异、制备简单等优势在金属的光生阴极保护领域得到了广泛关注。但是，TiO₂半导体材料禁带宽度较大，光响应范围窄，光吸收局限于紫外光区，除此之外，高的光生载流子复合率，也大大影响了TiO₂半导体材料的光电性能。针对这些缺点，本文采用窄禁带半导体与TiO₂半导体复合的方式，增强材料的光生阴极保护性能。首先，使用二次阳极氧化法在钛片基板上制备排列整齐的TiO₂纳米管阵列，然后通过连续离子层吸附反应法、化学浴法以及水热法等在其表面修饰Fe₂O₃、Bi₂Ti₂O₇和In₂S₃纳米颗粒。利用扫描电子显微镜（SEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）等对复合材料的微观形貌、晶相、元素组成等进行表征，并利用电化学手段研究复合材料对金属的光生阴极保护效果。

(1) 利用化学浴法在TiO₂纳米管表面制备了Fe₂O₃纳米颗粒，通过改变制备过程中铁源（Fe(NO₃)₃）溶液浓度来改变Fe₂O₃纳米颗粒的负载量。检测表明当Fe(NO₃)₃溶液浓度为0.05 mol/L时，在间歇可见光下与304不锈钢偶联时的开路电位降为500 mV，光致电流密度为40 μA/cm²，对304不锈钢的光生阴极保护性能最佳。由于电荷积累，Fe₂O₃与TiO₂接触界面会形成有效异质结，使导带相对位置变化，促进电子传输，提高光生阴极保护性能。

(2) 采用水热法成功在TiO₂纳米管表层制备了八面体结构的Bi₂Ti₂O₇纳米粒子，通过电化学方法研究了Bi₂Ti₂O₇/TiO₂纳米复合材料对304不锈钢以及Q235碳钢的光生阴极保护性能。间歇可见光下，Bi₂Ti₂O₇/TiO₂复合材料与304不锈钢耦合电位降为670 mV，光致电流密度为45 μA/cm²；Bi₂Ti₂O₇/TiO₂复合材料与Q235碳钢耦合电位降为330 mV，光致电流密度为30 μA/cm²。通过研究发现，Bi₂Ti₂O₇/TiO₂纳米复合材料对304不锈钢以及Q235碳钢都有一定的光生阴极保护效果。

(3) 通过连续离子层吸附反应法在TiO₂纳米管上制备了In₂S₃纳米颗粒，研究In₂S₃/TiO₂纳米复合材料在不含空穴捕获剂的溶液中对304不锈钢的光生阴极保护性能。In₂S₃纳米颗粒修饰后的复合材料禁带宽度较窄，光响应性能增强，对304不锈钢的光生阴极保护性能得以提升。当In₂S₃沉积次数为35次时，在3.5% NaCl溶液中可见光下对304不锈钢有最佳的光生阴极保护效果。

This study pays attention to the photocathode protection, a newly developed corrosion protection methods for metals, and discusses the photocathode protection performance of several nanocomposites under visible light. TiO₂ has attracted wide attention in the field of photocathode protection due to the advantages of low cost, non-toxic, chemical stability, excellent photoelectric performance as well as simple preparation. However, because of a large band gap, TiO₂ possesses a narrow light response range, which can only absorb ultraviolet light. Besides, the photovoltaic properties of TiO₂ are also affected immensely by its high recombination rate of photogenerated carriers. In response to these shortages, narrow gap semiconductors were combined with TiO₂ to enhance the photocathode protection performance of composites. Firstly, the TiO₂ nanotube arrays were prepared on the titanium substrate by two-step anodization. Subsequently, Fe₂O₃, Bi₂Ti₂O₇ and In₂S₃ nanoparticles were modified on the TiO₂ nanotube arrays by successive ionic layer adsorption and reaction (SILAR) method, chemical bath and hydrothermal method. The morphology, crystal structure and element state of the composites were observed by scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The photocathodic protection properties of composite materials for metal were discussed by electrochemical method.

1. Fe₂O₃ nanoparticles were decorated on the surface of TiO₂ nanotube by chemical bath method. The amount of Fe₂O₃ nanoparticles was changed by changing the concentration of iron source (Fe(NO₃)₃) in the preparation process. The results declared that when the concentration of Fe(NO₃)₃ solution was 0.05 mol/L, the open circuit potential decreased to 500 mV and the photoinduced current density was 40 μA/cm², which was the best one for the photocathodic protection for 304 stainless steel. Due to the charge accumulation, the contact interface between Fe₂O₃ and TiO₂ will form an effective heterojunction, which changes the relative position of the guide band, promotes the electronic transmission and improves the photocathode protection performance.
2. The octahedral Bi₂Ti₂O₇ nanoparticles were successfully prepared on the TiO₂ nanotube by hydrothermal method. Then the photocathode protection properties of Bi₂Ti₂O₇/TiO₂ nanocomposites for 304 stainless steel and Q235 carbon steel were analyzed by electrochemical method. Under the intermittent visible light, the coupling potential of Bi₂Ti₂O₇/TiO₂ composite and 304 stainless steel decreased to 670 mV, and the photoinduced current density was 45 μA/cm², while the coupling potential of Bi₂Ti₂O₇/TiO₂ composite and Q235 carbon steel decreased to 330 mV, and the photoinduced current density was 30 μA/cm². It turned out that Bi₂Ti₂O₇/TiO₂ nanocomposite owned an outstanding photocathode protection for 304 stainless steel and Q235 carbon steel.
3. In₂S₃ nanoparticles were loaded on TiO₂ nanotube by successive ionic layer adsorption and reaction method. The photoinduced cathodic protection properties of In₂S₃/TiO₂ nanocomposites for 304 stainless steel without hole trapping agent was researched. It illustrated that In₂S₃/TiO₂ nanocomposites owned narrow band gap and excellent light response, enhanced photoresponse performance and superior photocathodic protection performance for 304 stainless steel. When the number of In₂S₃ deposition was 35 times, the photocathode protection on 304 stainless steel under visible light in 3.5% NaCl solution was optimal.