可见光响应氮掺杂钽基纳米半导体光催化剂的可控制备及光解水制氢性能研究

The development of novel visible-light-driven semiconductor photocatalysts with higher activity and stability for photocatalytic water splitting into hydrogen has important scientific significance and wide application prospect. In this project, a series of nanosized tantalum-based semiconductor photocatalysts (< 50 nm) will be controllably synthesized via a facile, environment-friendly and general hydrothermal route. The particle size, morphology, crystal form and exposed crystal facets of tantalum-based semiconductors can be well controlled by simply adjusting the hydrothermal reaction parameters. The optimized tantalum-based semiconductors not only exhibit larger specific surface areas, more catalytic reaction active sites and higher ratio of exposed active facets, but also can be very easily doped by the nitrogen element in depth for highly efficient visible light absorbance, which provides reliable guarantee for the following excellent visible-light response photocatalytic activity. On this basis using the above ultrafine tantalum-based semiconductor nanoparticles as precursors, highly efficient visible-light response nitrogen-doped nanosized tantalum-based semiconductor photocatalysts can be prepared by hydrothermal method and traditional gas phase or solid state reaction method under ammonia atmosphere, and their photocatalytic water splitting performances will also be evaluated under visible-light irradiation. Furthermore, the relationships between structures of tantalum-based semiconductor photocatalysts and their photocatalytic performances, and the photocatalytic reaction mechanism will be systematically investigated in depth, which may provide general rules for the design of novel visible-light response photocatalysts with higher efficiency and stability in future.

发展新型、高效、稳定的可见光响应型光解水制氢半导体光催化材料具有重要的科学意义和广阔的应用前景。本项目拟设计开发一种简易、普适、绿色的水热合成方法来实现一系列纳米级（< 50 nm）钽基半导体材料的化学控制制备。通过调变水热反应参数等实现纳米级钽基半导体材料的尺寸、形貌、晶型和暴露晶面等的精确调控。优化后的超细钽基半导体纳米颗粒除了具有大的比表面积、更多的催化活性位点和大比例暴露的高活性晶面，还特别有利于氮元素的深度掺杂实现其对可见光的高效吸收，为下一步获得优异的可见光催化性能提供了可靠保障。在此基础上，以这些超细钽基半导体纳米颗粒为前驱体，通过水热法和气相、固相反应氮化法等实现高效可见光响应的氮掺杂纳米级钽基半导体光催化材料的可控制备，并将其应用于光解水制氢。系统深入地研究钽基半导体光催化材料的构效关系及光催化反应机理，为开发新型、高效、稳定的可见光催化材料提供通用的设计准则。

发展新型高效稳定的半导体基纳米复合可见光催化剂是提高太阳能利用率，最终实现太阳能光催化技术产业化应用的关键。本项目采用水热法、乳液自组装等方法成功制备了一系列新型高效半导体基可见光催化剂，如N掺杂SrTa4O11纳米线、Sn2Ta2O7纳米片、自组装Au/CdSe纳米晶团簇等，这些半导体基纳米催化剂在可见光催化分解水制氢方面表现出优异的催化活性和循环稳定性，为开发和设计新型高效的半导体基纳米光催化剂提供了新思路和新途径。代表性工作如下：1）发展了一种简单、有效的基于钽酸为前驱体的固相合成方法，成功实现了Sn2Ta2O7纳米片的可控制备。Sn2Ta2O7纳米片光催化剂在可见光催化分解水制氢时表现出比块体更好的催化性能; 2）发展了一种简单、有效的乳液自组装方法，成功实现了一系列不同Au尺寸与含量的Au/CdSe纳米晶团簇，该Au/CdSe组装体表现出极高的可见光催化产氢活性（73 mmol gCdSe-1 h-1，约为CdSe组装体的10倍），且具有良好的催化稳定性（> 50 h），为设计合成其它等离子体增强光催化材料提供了基础；3）开发了一种新型的碱辅助合成方法成功制备了富含氮缺陷的石墨相氮化碳（g-C3Nx），其良好的可见光吸收特性以及光生电子-空穴分离能力使得其光催化产氢速率得到大幅提升；4）设计合成了氮掺杂浓度连续可调的CQDs，且掺杂浓度不改变N-C键构型，氮掺杂元素的引入可以有效抑制CQD光生电子被捕获态能级弛豫，进而促进电荷分离。这种氮掺杂浓度可控的合成方法为优化设计CQDs基光催化材料提供了新的策略；5）发展了一种简单、廉价、绿色的水热合成方法，成功实现不同厚度SnNb2O6纳米片的可控制备，其中超薄SnNb2O6纳米片表现出更好的催化产氢活性，这为设计合成其它类型的纳米铌酸盐光催化材料奠定了基础。