具有紫外-可见-近红外宽光谱响应的纳米复合中空纤维的制备及其光催化性质研究

Recently, the fabrication of TiO2 based photocatalyst with large solar sunlight harvesting region and low recombination rate of photogenerated carriers has received much more research attention. In this project, we plan to employ rare earth-doped upconvering phosphors NaFY4:Ln (Ln=Yb3+,Er3+,Tm3+,Ho3+) as sensitizing agent to fabricate novel one-dimensional nanocomposite photocatalyst with UV-Vis-NIR response properties via loading visible light photocatalyst Ag@AgX (X=Cl, Br, I) to NaYF4:Ln/TiO2 nanocomposite hollow fibers synthesized by directly annealing of the electrospun composite fibers. The upconversion process of NaYF4:Ln nanocrystals could convert NIR to UV and visible light, which can be harvested by TiO2 and Ag@AgX, respectively. The bandgap match between TiO2 and Ag@AgX facilitates the electron-hole separation and restricts the recombination of photogenerated carriers. These advantages make the nanocomposite photocatalyst exhibit UV-Vis-NIR harvesting and low recombination rate of photogenerated carriers, which would extend photocatalyst harvesting region and enhance the photocatalytic activity. On the basis of the investigation of the influence of the composition, structure and morphology of the photocatalyst on its potocatalytic activity under visible light and near infrared light, we want to reveal the intrinsic relationship between energy transfer process between the components of the nanocomposite photocatalyst and its photocatalytic activity and develop novel one-dimensional nanocomposite photocatslyst with high catalytic activity. The research result of this project has an important scientific significance for fabricating novel TiO2 based photocatalyst with high photocatalytic activity and promotion its application in environmental remediation and energy conversion.

本项目针对目前制约TiO2光催化剂应用所存在的太阳光谱响应范围窄和载流子复合几率高的关键问题，以稀土上转换发光纳米材料NaYF4:Ln (Ln为稀土离子)为光敏化剂，通过直接煅烧电纺前驱纤维法制备NaYF4:Ln/TiO2复合中空纳米纤维，并以此为载体负载可见光催化剂Ag@AgX。利用NaYF4:Ln的上转换特性将太阳光中的近红外光转化为紫外光和可见光，结合TiO2与Ag@AgX的协同催化效应促使光生载流子得到有效分离从而抑制激子复合，提高太阳光利用率和光量子效率，制备具有紫外-可见-近红外光宽光谱响应特性和低载流子复合几率的新型高效纳米复合光催化剂。研究纳米复合光催化剂的组成、结构和形貌对其在可见光和近红外光下催化性质的影响，揭示纳米复合光催化剂的能量传递过程与其催化活性之间的内在关系。本项目发展新型高效的纳米光催化剂和推动TiO2基光催化剂在环境修复及能源转化中的应用具有重要意。

利用光催化技术消除大气与水中有机污染物近年来受到了科研人员的广泛关注，实现光催化剂大规模应用的关键是获得具有宽太阳光谱响应及低载流子复合几率的光催化剂。本项目研究开发结构新颖，太阳光谱响应宽，载流子复合几率低的新型光催化剂，为新型光催化剂的研究及应用提供可靠的实验依据和理论指导，推动新型光催化剂的发展。取得主要结果如下：. （1）制备出了具有多孔结构的BiVO4光催化剂，并探讨了煅烧温度对其结晶性、孔结构及相应光催化性能的影响；. （2） 制备出了ZnMn2O4/还原氧化石墨烯（RGO）复合纳米棒，RGO的添加可有效改善材料的导电性；. （3）制备出了具有紫外-可见光响应特性的TiO2/ RGO /Ag复合光催化剂，RGO和银纳米颗粒的引入对拓展TiO2的光吸收范围及抑制光生载流子的快速复合，提高TiO2的光催化效率具有重要作用；. （4）采用超声化学法制备了TiO2/AgBr纳米复合光催化剂，AgBr的加入可有效拓展TiO2的光吸收范围并抑制光生载流子的快速复合，提高TiO2的光催化效率。. 上述结果表明，通过调节光催化剂的孔结构及引入RGO和可见光催化剂可改善材料的导电性、拓展光吸收范围及抑制光生载流子的分离，改善催化剂的光催化效率，最终得到性能优异的光催化剂。