g-C3N4/贵金属/铋基半导体Z机制光催化体系构筑、机理和性能研究

It is difficult for the present traditional photocatalytic systems to simultaneously possess the high charge-separation efficiency and strong redox ability，which hinder the widely application of photocatalytic technique. In this project, the proposed Z-scheme photocatalytic systems of g-C3N4/Nobel metal/Bismuth-based semiconductor photocatalyst could overcome the drawbacks. Firstly, porous g-C3N4 will be synthesized by a simple technique and an anisotropic Z-scheme photocatalytic of g-C3N4/Nobel metal/Bismuth-based semiconductor will be constructed via photo reduction and wet chemistry methods, in which nobel metal is used as a solid-state electron mediator. The effect of the varying parameters of fabrication on morphology, composition, structure of Z-scheme system will be systemtically investigated. The interactions and charge-transfer mechanisms between heterojunction interfaces will be revealed. Secondly, photocatalytic activities of the Z-scheme photocatalytic system will be evaluated by the degradation of organic compound in solution or NO in air under visible-light. Photocatalytic mechanisms will be explored by using active species trapping method and performing superoxide radical quantification experiments. The structure-activity relationship between photocatalyst and mechanism of degradation is discussed. Finally, the conduction of this project will provide new ideas for the design and fabrication of heterogeneous Z-scheme photocatalytic systems, meanwhile, the application of Z-scheme photocatalytic of g-C3N4/Nobel metal/Bismuth-based semiconductor can produce prominent environmental and economic benefits.

针对目前传统催化剂不能兼有氧化还原能力强、载流子分离和传输效率高等特点，本项目提出构筑负载贵金属的多孔g-C3N4/铋基半导体Z机制光催化体系的研究思路：首先，采用简单剥离法制备薄层多孔g-C3N4；以其为载体，运用光还原法和湿化学法构筑基于贵金属电子介体的g-C3N4/铋基半导体Z机制光催化体系，系统研究生长过程对复合光催化体系的组成、微结构和形貌的影响规律，揭示异质界面之间的相互作用和电荷传输机制；其次，以液相中的有机污染物和空气中的有害气体NO为目标探针，探究其可见光降解和去除特点，分析降解和去除过程中的活性物种信息，厘清其构-效关系，阐明光催化降解和去除机理；最后，研制出稳定性好、可见光活性高和环境效益良好的光催化剂材料，并探索拓展其在环境保护领域的应用功能。

光催化技术在解决新能源和环境问题方面具有广阔的应用前景。在提高光催化剂性能的方法中，异质结的构筑被证明是促进载流子的分离最灵活而有效的途径。本项目围绕两大热点光催化材料g-C3N4和铋基半导体为中心，利用水热法、溶剂热法、静电纺丝法、离子交换及光还原法等方法成功开发了多种新颖的性能良好的异质结构光催化剂，如: BiVO4/g-C3N4、Bi2WO6/g-C3N4、Bi2WO6/B2O3、BiVO4/B2O3、Bi4O5I2/Bi2S3、ZnCdS/g-C3N4、Cu2O/g-C3N4和S-dopeed ZnO/g-C3N4等Z型、n-n、n-p型异质结构。另外，我们基于助催化剂理念拓展了CdS纳米微球负载与NiS2量子点体系及非晶NiS薄膜包覆超细Zn0.5Cd0.5S复合体系等。以光降解有机污染物、光催化去除NO及光催化产氢为指针系统研究了材料组成、形貌对材料光吸收性质和载流子分离规律性的影响，发现形成特殊结构的异质结构不仅有利于光生载流子的分离效果，还能够提高光催化体系的稳定性。通过构建核壳结构、原位生长花状结构、空心结构及多孔结构发现可以有效增强光吸收能力。系统阐述了Z型、n-n 型、n-p型及助催化剂参与的异质结构在光催化过程中对光生载流子分离和迁移的作用机制，明确了形貌结构及相互空间结合特点对载流子传输及分离的重要性；证实了各类异质结构的工作机制和活性位点的分布规律，特别是证实了非晶工程在助催化剂设计方面突出的优势。以上成果为开发新型异质结构光催化剂或提高光催化效率提供了实验依据。