铌（钽）酸盐/氮化碳复合纳米片分解水制氢催化剂的构筑及其催化机理研究

Water splitting under sunlight has been regarded as an optimal way for the production of renewable hydrogen. Composite nanosheet photocatalyst has been considered as an important type of photocatalysts for the hydrogen production owing to its advantages in the composite nanosheet photocatalytic system, such as large contact area and strong electronic coupling. The niabate (tantalate)-based nanosheets, such as HCa2Nb3O10, KCa2Nb3O10 and HCa2Ta3O10, have the high stability and high conduction band position. However, such nanosheet photocatalysts cannot work under visible light irradiation. In this project, to address this problem for the niabate (tantalate)-based nanosheets, graphitic cabon nitrogen (g-C3N4) is used to construct a series of niabate (tantalate)/g-C3N4 composite nanosheet photocatalysts. This project will construct the control models of the composition, surface structure, and interfacial structure for the niabate (tantalate)/g-C3N4 composite nanosheet photocatalysts. The effects of composition, content, microstructure, and bandgap structure of the photocatalysts on the photogenerated electron tranfer and photocatalytic hydrogen production activity will be systematically investigated. The possible mechanisms of the enhanced quantum efficiency, enhanced photocatalytic activity, and photocatalytic hydrogen production reaction under visible light irradiation will be proposed. The ultimate aim of this project is the development of visible-light-driven niabate (tantalate)/g-C3N4 composite nanosheet photocatalysts with high photocatalytic activity. It is hoped that this project could provide theoretical and experimental basis for the design of highly effective visible-light-driven composite nanosheet photocatalyst for the hydrogen production.

太阳能光解水制氢技术是获取氢能的最理想途径之一。复合半导体纳米片光催化剂具有界面接触面积大、电子耦合作用强等优点，成为光解水制氢催化剂研发的一类重要材料。本项目针对具有高稳定性、高导带位置HCa2Nb3O10、KCa2Nb3O10、HCa2Ta3O10等铌（钽）酸盐纳米片存在无法响应可见光的问题，提出利用纳米片状石墨相氮化碳（g-C3N4）改性该类铌（钽）酸盐纳米片，构筑新型铌（钽）酸盐/g-C3N4复合纳米片可见光光催化剂的研究思路。建立该类复合纳米片催化剂组成与微观表面、界面结构的调控模型，研究复合纳米片组成比例、微观结构以及能带结构等因素对光生电子迁移行为以及产氢性能的影响，分析催化剂量子效率以及催化活性增强机制，揭示该类复合纳米片可见光光催化机理，最终开发出高活性可见光响应型铌（钽）酸盐/g-C3N4复合纳米片分解水制氢催化剂，为构筑高效复合纳米片可见光光催化剂提供实验和理论依据。

本项目针对单一纳米片光催化剂存在的光催化活性低的问题，设计与构筑了系列纳米片基复合光催化剂，并对其光催化分解水产氢、光催化降解污染物等性能进行了研究，阐明了光催化性能增强机制。项目取得的主要结果如下：. 1、纳米片复合光催化剂的构筑及其规律.发展了液相化学剥离法或水热法制备铌酸盐或钽酸盐纳米片光催化材料，构筑了KCa2Nb3O10/g-C3N4、KCa2Ta3O10/g-C3N4、SnNb2O6/g-C3N4等复合纳米片异质结光催化剂。主要研究了化学组分、表面性质及复合比例对构筑复合纳米片的影响，建立了铌酸盐、钽酸盐超薄纳米片以及氮化碳光催化剂制备过程的组成结构的调控模型。并将合成方法拓展到KCa2Nb3O10/WO3、TiO2/SnNb2O6、CaIn2S4/g-C3N4等纳米片异质结复合光催化剂的构筑中，实现了该类光催化剂的可控制备。. 2、纳米片复合光催化剂电荷分离与迁移性能及其规律.总结了KCa2Nb3O10/g-C3N4、KCa2Ta3O10/g-C3N4、SnNb2O6/g-C3N4等复合纳米片光催化体系中，化学组成、复合比例、能带结构等因素对复合光催化体系中光生电子与空穴迁移行为的调控规律，发现了形成的二维-二维界面、零维-二维界面具有界面接触面积大、电子耦合作用强等特性，从而可有效抑制光生载流子复合，增强光生电荷利用率与光催化效率。结合可见光吸收性能以及组成结构、比表面积分析，阐明了纳米片复合光催化剂增强的光生电荷分离与迁移性能为光催化活性提高的主要原因。. 3、可见光光催化性能及其构效关系.获得了可用于高效光催化分解水产氢、光催化降解水中抗生素的铌酸盐、钽酸盐基以及氮化碳基纳米片复合光催化剂，解决了目前该类催化剂存在的量子效率低、活性不理想的关键问题，可见光吸收阈值显著增加，产氢量子效率达到3.2%，且具有较好的稳定性。阐明了典型II型、Z型、I型光催化体系、等离子体光催化剂中电荷有效利用和光催化性能增强的协同机理。建立了纳米片复合催化剂可见光催化机理模型，为设计制备高效、可见光响应的纳米片复合光催化剂奠定坚实的理论基础。. 总之，我们在项目执行期间，获得了大量有价值的研究成果。发表与本项目相关的SCI论文22篇，申请国家发明专利9项。