钙钛矿氧化物/g-C3N4异质结的结构设计及其可见光催化性能研究

The rapid development of modern industry using the consumption of non-renewable fossil fuels has caused a serious global energy shortage and environmental pollution. Water splitting for hydrogen evolution and organic pollutants degradation by utilization of solar energy could be one of the effective ways to solve these problems. The design and preparation of semiconductor photocatalysts with high photocatalytic efficiency and visible light response has important scientific significance and application prospect. Graphitic carbon nitride (g-C3N4) was found to be an environment-friendly material with high chemical stability, but the narrow response range to visible light and low quantum efficiency lead to low photocatalytic activity. Based on the special crystal structure and electronic properties of perovskite oxides, this project utilizes perovskite and g-C3N4 to construct the heterojunction photocatalytic materials. The energy band structure is regulated and a new type of photocatalytic material with wide visible spectrum response and high photocatalytic activity is obtained by changing the composition, morphology and structure of perovskite. The effects of the composition, morphology and band structure of the perovskite on the formation of the heterojunction are investigated in detail. The energy band regulation and the separation and interface transfer of photogenerated carriers of the perovskite oxide /g-C3N4 heterojunction are studied. In comparison with the photocatalytic experimental results, the mechanism of hydrogen evolution and organic pollutants degradation and the structure-activity relationship are elucidated. The results of this project will be the theoretical and experimental basis for the structural design and practical application of new visible light driven photocatalysts.

能源危机和环境污染是当今人类面临的两大难题。利用太阳能光解水制氢和光催化降解有机污染物，是解决能源和环境问题的有效途径，其关键在于设计合成高效、可见光响应的光催化剂。石墨相氮化碳具有环境友好和化学稳定高的特点，但其可见光响应范围窄、量子效率低，导致其光催化活性低。本项目利用钙钛矿型氧化物晶体结构和能带结构可调节性大特点，系统性的设计合成钙钛矿氧化物/g-C3N4 异质结构，探讨其电子转移和传递性质以及光催化性能。拟选择AFeO3、AVO3、ABiO3、ANiO3 四种钙钛矿氧化物，通过阴、阳离子掺杂改变钙钛矿氧化物组成、形貌和结构，以调控其能带结构，获得宽可见光谱响应、高催化活性的可见光催化剂；研究钙钛矿氧化物组成、形貌和能带结构对异质结形成的影响；结合光催化实验结果，采用光电化学方法探讨钙钛矿氧化物/g-C3N4 异质结能带调控和光生载流子的分离和界面转移，阐明光解水制氢和光催化降解有机污染物的作用机制。探讨钙钛矿氧化物/g-C3N4 异质结光催化材料结构和光催化性能之间的关系，为新型可见光催化材料的结构设计和实际应用提供理论及实验依据。

设计合成稳定、高效的可见光催化剂，提高光生电荷的分离效率和光催化反应的表观量子产率，是将光解水制氢、光降解有机污染物的研究推向实际应用时，亟需解决的关键科学问题。半导体异质结构的形成，有助于增加载流子寿命、提高界面电荷迁移速率，从而提高光催化量子效率。本项目通过调控钙钛矿氧化物A位阳离子种类及含量，调节其能带结构，以增强其可见光吸收能力。在此基础上，构筑不同类型的钙钛矿氧化物/g-C3N4异质结可见光催化剂，包括Ⅱ型、p-n型和Z型异质结等。Z型异质结具有宽可见光响应、高光生载流子分离效率和强氧化还原能力。p-n型异质结通过建立界面间的内电场促进光生电荷分离。本项目通过构筑p-n型和Z型异质结，获得了稳定、高效的可见光催化剂。采用光电化学方法、PL和TRPL光谱，探讨不同类型异质结光生电荷分离、转移和传递的规律。阐明光生电荷转移和迁移行为对光解水制氢和光降解有机污染物的影响。通过调控钙钛矿氧化物/g-C3N4异质结能带结构，实现对光生电荷分离、转移和传递过程的有效控制。本项目制备了一系列不同类型的异质结，包括：LaFeO3/g-C3N4（Z型）、ErFeO3/g-C3N4（p-n型）、EuVO4/g-C3N4（p-n型）、Cu2V2O7/Cu3V2O8/g-C3N4（Z型）、DyFeO3/g-C3N4（p-n型）、Sc2VO5-δ/g-C3N4（表面缺陷调控，Ⅱ型）等。其吸附能力、光解水制氢、光催化、光芬顿催化降解有机污染物及抗菌活性均得到显著提高。本项目的研究可为构筑高效光生电荷分离和转移的异质结界面提供实验参考。