上转换NaLnF4(Ln=Y,Gd,La和Ce)@WO3-x-Au材料的构建及其可见-近红外光催化作用研究

Direct application of the photocatalysis for energy shortage and environmental pollution has become the focus of people's attention. In order to design a wide spectral response (visible - near infrared spectra), high photocatalytic activity and stability and high efficiency of solar energy utilization about photocatalytic materials, the project proposed the mechanism and experimental method of layer-by-layer assembly technology to build the NaLnF4@WO3-x-Au multi-stage nano/micro heterostructure. Combined with the advantage of up-conversion luminescence (infrared light excitation to emit visible light) of NaLnF4 and LSPR effect induced by Au nanoparticles and WO3-x under visible light irradiation, a structure-function relationship among LSPR effect, fluorescence up-conversion and photocatalytic activity was built to reveal the synergistic effect of fluorescent up-conversion function on the rare earth materials and LSPR effect of Au and WO3-x in photocatalysis. It was mainly to investigate the effect about the different rare-earth activator of Ln ions, alcoholysis time of tungsten precursor, the component proportion, the size and configuration of Au nanoparticles, oxygen vacancies in the WO3-x and the temperature and time of the activating thermal treatment to determine the composition of the multilevel nano/micro heterostructure material with high catalytic activity and influencing rule on the degradation of pollutants and photocatalytic oxidation of CO under visible-NIR light. Preparing the multi-stage nano/micro structure photocatalyst with high activity and wide visible-NIR spectral response has also the feature of easy recycle, which providing theoretical guidance for developing a new visible-NIR photocatalytic material.

光催化应用于能源短缺与环境污染已成为人们关注的焦点。为开发宽光谱响应（可见-近红外光谱）、高活性和稳定性、高太阳能利用率的光催化材料，本项目拟通过层层组装构筑NaLnF4@WO3-x-Au多级纳/微异质结构，结合NaLnF4的荧光上转换（红外光激发出可见光）、Au纳米粒子和WO3-x可见光激发产生LSPR效应的优势，建立LSPR效应-荧光上转换-光催化活性间的构效关系，揭示稀土荧光上转换功能和Au、WO3-x的LSPR效应在光催化反应中的协同作用。主要考察不同的稀土激活剂Ln离子、醇解时间、组分配比、Au粒子尺寸和构型、WO3-x的氧缺陷及活化热处理温度时间的影响，确定具有高活性多级纳/微异质结构材料的组成，在可见-近红外光下对污染物降解和光催化氧化CO的活性影响规律。研制出高活性的宽光谱响应多级纳/微异质结光催化剂也有易回收使用的特点，为开辟新型可见-NIR光催化材料提供理论指导。

为提高光催化材料的光生载流子分离和迁移效率以及对太阳光的利用率，本项目提出了将NaYF4:Yb3+, Er3+、YF3: Yb, Er、Lu3NbO7: Yb, Ho等有效的上转换材料对可见光响应的金属硫/氧化物（ZnS、ZnIn2S4、In2S3和氧化钨）、Ag2CrO4和InVO4等半导体进行改性，即形成直接掺杂型和上转换异质结复合型材料。通过一系列的表征方法对光催化剂的物理化学性质进行了研究，并进行了在全光谱和不同波段光源(UV，Vis或NIR)照射下的光催化实验，发现一方面上转换材料与半导体之间发生了高效的能量转移过程，可以实现近红外光的有效利用；一方面引入上转换材料具有更快的光生载流子分离和迁移速率以及更高的载流子浓度；由此使得光催化剂在光解水制氢、产H2O2和污染物处理呈现出优越的光催化活性和稳定性，同时结合电子顺磁共振等技术和捕获剂实验提出了相应的反应机理。本项目的研究结果为构建全光谱吸收光催化剂提供了研究方法和技术支持，丰富和发展了光催化基础理论知识，具有重要理论价值和实际意义。