广谱光吸收的上转换发光增强3C-SiC纳米复合结构设计及光解水研究

In order to maximize the use of sunlight, the idea of upconversion luminescence enhanced light absorption of photocatalytic materials is introduced to the design of new style water splitting system. Choosing 3C-SiC nanocrystals with excellent properties as photocatalystic materials, upconversion luminescence nano-materials with tuned luminescence properties is combined with 3C-SiC nanocrystals to form upconversion luminescence materials/3C-SiC nanocrystal composite structure with broad spectrum light absorption ability and high photocatalytic activity, and then connected with ion doped TiO2 nanotube arrays with outstanding characters to constructure new style self-driven water splitting system. The effects of size, microstructure and surface characters of 3C-SiC nanocrystals on their band gap structure and spectral response characteristics are analyzed mainly based on the design and preparation of upconversion luminescence enhanced 3C-SiC nanocrystal composite structure in this project. The regulation and control principle of luminescence behavior of rare earth elements doping upconversion nanomaterials is explored, and the effect of spatial distribution of upconversion luminescence nano-materials and 3C-SiC nanocrystals on photon transportation and absorption process in the composite structure, in other words, the enhancement role of upconversion luminescence to light absorption of 3C-SiC nanocrystal, is also analyzed here. The formation, transportation of charge carriers in 3C-SiC nanocrystals and TiO2 nanotube as well as the interaction of charge carriers with water molecules when they reach their surfaces are researched. At last, the design principle of new style water splitting system with high conversion efficiency is also proposed in this project.

为最大程度利用太阳光，将"上转换(UP)发光增强光吸收"的思想引入光解水体系的设计中，选择特点突出的3C-SiC纳米晶为光催化材料，将其与UP发光材料有机结合，通过对UP发光材料发光行为进行调谐，获得具有广谱光吸收能力和高光催化活性的UP发光稀土氧化物/3C-SiC纳米复合结构，并将其与离子掺杂TiO2纳米管阵列结合，构建自驱动光解水系统。本项目以UP稀土氧化物/3C-SiC纳米复合结构的设计与制备研究为前提，重点研究3C-SiC纳米晶结构及表面特性等对其能带结构及光谱响应特性的影响规律；探索UP纳米材料发光行为（激发与发射）的调谐机制；通过纳米复合结构设计揭示UP发光对3C-SiC光谱响应的增强机理；分析3C-SiC纳米晶表面结构及其与水分子的相互作用机理；探讨3C-SiC纳米晶中载流子的产生、输运及运达表面后与水分子的相互作用及调控机制，提出新型高效光解水系统的设计新原理。

21世纪，能源危机和环境污染问题是世界各国共同关注的两大主题。半导体光催化技术，作为有望治理环境污染和解决能源危机的有效途径，引起了国内外研究者的大量关注。该技术的关键在于光催化材料，通常高光催化活性的材料带隙一般较宽，只能吸收仅占太阳光谱5%左右的紫外光等短波光，因此开发具有广谱光吸收的新型光催化材料具有重要意义。本课题采用化学刻蚀辅助超声振荡的方法制备了3C-SiC纳米晶，研究了刻蚀时间对3C-SiC纳米晶尺寸及光吸收性能的影响；其次，采用化学共沉淀法和碳球模板法分别制备了不同结构形貌的稀土氧化物上转换发光材料，探究了Er/Tm、Yb的掺杂量以及前驱体溶液浓度、模板使用量对样品上转换发光性能的影响。在此基础上，首次借助多巴胺自聚合作用分别制备了链状和片状Er/Tm//Yb/Y2O3上转换发发光材料增强3C-SiC纳米晶的复合结构，研究了两种结构对复合样品光吸收性能的影响，评估了复合样品的近红外光及紫外-可见-红外光光催化活性，并分析了Er/Tm//Yb/Y2O3上转换发发光材料对3C-SiC纳米晶的光催化增强机制。研究结果表明，Er/Tm//Yb/Y2O3上转换材料可将980 nm的近红外光转换为3C-SiC纳米晶可吸收的蓝光和绿光，且链状样品的发光性能远远高于片状样品；链状Er/Tm//Yb/Y2O3-SiC复合样品较片状复合样品具有更高的近红外光光催化活性，且两种复合结构在Xe灯照射下均具有优于纯3C-SiC纳米晶的光催化活性。探讨了3C-SiC纳米晶中载流子的产生、输运及运达表面后与水分子的相互作用及调控机制，对构建广谱光吸收的新型光催化材料提供重要理论和实际基础。