表面等离子体耦合宽频上转换增强TiO2光催化性能研究

Aiming at the low utilization efficiency of solar light by the TiO2 photocatalyst, the combination of localized surface plasmon resonance effect and rare-earth free upconversion emission is proposed to improve the photocatalytic efficiency of TiO2 by construction a novel photocatalysis system based on the coupling of surface plasmon and wide-frequency upconversion emission, which could achieve the optical frequency conversion and synchronous fluorescent enhancement. The purpose of this study is to design and synthesis a series of nano photocatalysts with core-shell structure, select and construct of efficient TiO2 photocatalysis system to improve the quantum efficiency of photocatalytic reduction of CO2 by the optimization of reaction conditions. The effort will be devote to the controllable preparation of metal particle and upconversion materials with nano-structure, and regulating their element components, structures and properties by exploring effective synthesis methods. In addition, the coupling between surface plasmon and upconversion emission, the efficiencies for light absorption, conversion and utilization, the photocatalysis mechanism will be analyzed in detail. Meanwhile, the mechanism of upconversion emission and fluorescence enhancement will be investigated under the assistance of fluorescence spectra and theoretical calculation, the influencing factors on the surface plasmon enhanced fluorescence and energy transfer will be studied as well. Simultaneously, the coupling mechanism model and light conversion and utilization model will be established, to obtain a new method for solar light frequency conversion and regulation. This project will provide new academic ideas for light energy utilization and photocatalysis system designing.

针对TiO2光催化剂对太阳光利用率低的问题，拟将局域表面等离子体效应和非稀土上转换发光结合，构建表面等离子体耦合宽频上转换新型纳米TiO2光催化体系，通过光频转换与同步增强，提高TiO2光催化效率。旨在设计合成系列纳米核-壳结构光催化剂，以提高光催化还原CO2量子效率为目标，优化反应条件，筛选构建高效TiO2光催化体系。通过制备方法的探索，实现对材料组成、结构与性能的调控，重点研究表面等离子体与上转换发光的耦合机制，核-壳结构催化剂的光能吸收、转换、利用效率，及光催化反应机理。借助荧光光谱和理论计算等手段，探索发光机制和荧光增强机理，弄清表面等离子体与荧光增强、能量传递之间的影响因素，最终建立荧光增强耦合机制模型和光能转换利用模型，获得太阳能光频调控新策略。本课题将为光能利用和光催化体系设计提供新的学术思路。

针对TiO2光催化剂对太阳光利用率低的问题，项目将纳米颗粒的局域表面等离子体效应和上转换发光应用于提高TiO2的光催化效率，1）借助微波醇热法获得基于上转换发光的TiO2/CeF3复合光催化剂，CeF3可将420–600 nm的可见光转换为285–380 nm的紫外光，复合物具有可见光催化还原CO2活性；2）以Ti片为基底，在碱性水热/醇热环境中制备得到TiO2纳米片、纳米线、纳米草和纳米花等薄膜；3）采用微波协助化学还原法将Au、Ag、Cu颗粒负载在上述TiO2纳米薄膜表面，获得多种金属(Au、Ag、Cu)/TiO2等离子体光催化复合薄膜。研究结果显示，纳米Au、Ag、Cu在较优的负载量时，可使TiO2纳米薄膜的制氢、CO2还原制甲醇、光降解亚甲基蓝性能提高2.5—10倍。通过对比不同反应条件下的实验结果，初步提出了金属/TiO2体系光催化反应增强机制，即紫外激发-可见增强的协同光催化机制。同时发现Au/TiO2纳米草、Au/TiO2纳米片、Au/TiO2纳米线薄膜表面的纳米Au颗粒具有局域表面等离子体双峰吸收现象，该现象与常见纳米Au颗粒的LSPR单峰吸收截然不同。这是因为TiO2特殊的微观结构可以引起显著的光散射现象，增强了入射光与纳米Au的相互作用，并形成双峰吸收现象，极大增强了Au/TiO2对可见光的捕获程度，上述发现对高效光催化薄膜体系的设计提供了新的研究思路。