基于纳米异质结构筑的光电材料的可控制备及海工光电阴极保护机制研究

The South China Sea is one of the largest natural light sources in the world. Thus, using the cathodic protection with photoelectric effects has good natural advantages. The traditional photocathode protection system based on TiO2 can’t provide protection for metals with too negative self-corrosion potential, such as carbon steel. This is owing to the disadvantages of that the stop-band of TiO2 is too wide and the conduction band potential is not negative enough. In this protect, a nano-heterostructure protection system based on graphite-nitride carbon (g-C3N4) is proposed to build. The active sites of photo-electrochemical reaction are enhanced via the mesoporous and two-dimensional ultrathinization of a novel graphite-like carbon nitride g-C3N4 layered nanostructures. The electron mobility is improved by the recombination of graphene quantum dots and nitride carbon materials. The heterogeneous composite materials are prepared by the in situ synthesis of oxygen co-catalyst (Ru, Ni, Co) on nitrified carbon materials to improve the oxidizing ability of bare holes. At the same time, the separation efficiency of bare electron-hole is promoted through the establishment of heterogeneous junction electric field. The effects of the optimization of g-C3N4 nanostructures and the construction of heterostructures on the protective properties of photoelectric cathodic protection are studied. The photoelectrochemical cathodic protection mechanisms of optical anode materials based on g-C3N4 nanometer heterostructure in visible light are illuminated. Therefore, this project is of great significance both in theory and in reality.

南海是全球最大的天然光源区之一，利用光电效应进行阴极保护具有良好的天然优势。基于传统TiO2的光电阴极保护体系存在禁带宽、导带电位不够负的缺点，对海工混凝土结构中常见的自腐蚀电位较负的金属，如碳钢，无法进行保护。本项目提出构建基于石墨相氮化碳（g-C3N4）的纳米异质结保护体系，将g-C3N4层状纳米结构介孔化和二维超薄化，提升其光电化学反应活性位点；将石墨烯量子点与氮化碳材料进行复合，提升电子迁移率；采用析氧共催化剂（Ru、Ni、Co）在氮化碳材料上原位合成，制备异质结复合材料，提升光生空穴的氧化能力，同时通过异质结电场的建立，提高光生电子-空穴的分离效率。研究g-C3N4纳米结构的优化与异质结体系的构筑对其光电化学阴极保护性能的影响，阐明基于g-C3N4纳米异质结构筑的光阳极在可见光照射下对金属材料的光电化学阴极保护机制。因此，本项目无论在理论上，还是在现实上，均具有重要意义。

南海“高温、高湿度、高盐雾”恶劣环境对海洋工程装备的腐蚀防护提出了巨大挑战，利用南海光能全年可利用、高辐照的资源禀赋，发展零能耗、免维护、可持续的光电阴极保护技术具有重要的战略意义和科学价值。本项目围绕易腐蚀金属防护、黑暗状态保护、高效能就地保护等光电阴极保护领域难点问题，以氮化碳光阳极的“构效设计”、“载流子迁移路径设计”、“空穴生命总周期”的顺序路径为逻辑脉络，深度剖析了半导体材料属性、光电转换过程、金属腐蚀防护各阶段的相关科学问题。重要结论如下：（1）针对碳钢的难防护问题，通过构筑内置电场策略实现了氮化碳对易腐蚀碳钢的有效保护，揭示了氮化碳与金属腐蚀防护效能间的构效机制；（2）针对碳钢的黑暗状态难防护问题，通过设计疏松型氮化碳厚膜电极实现对碳钢的明/暗态高效能防护，系统的阐释了薄膜结构与黑暗状态储能之间的相关机制；（3）针对海洋环境难就地保护问题，沿着空穴的生命轨迹解决了空穴扩散路径及电解液-电极界面的弊端，构建了具有空穴自捕获功能的光电阴极保护体系，实现了海洋环境下对金属的长效稳定阴极保护；（4）针对就地保护效能低及相关机制不明晰等问题，基于液态捕获理念提出并构建了仿固态捕获体系，实现对金属的高效能就地保护；揭示了仿固态/液态捕获体系的工作机制。.本项目主要面向半导体与金属作为关键要素建立的新型光电阴极保护技术，对于先进光阳极材料的设计及其产业化应用具有重要的参考价值和奠基意义。