ZnTe基多元纳米复合结构的电子转移机理及在CO2光化学还原中的应用

太阳能转化二氧化碳是解决化石燃料排放和新能源制造的有效绿色途径之一，其关键是提高光催化剂的效能。本课题拟合成基于ZnTe的多组份、Z型复合结构的CO2 光还原催化剂。ZnTe光激发电子的超快转移动力学和还原能力将通过对CO2单电子的激活，有效降低CO2在光还原过程中的动力学阻碍，从而提高整个还原反应的效率。以此材料构筑的核壳纳米结构不仅有利于光生电子-空穴对的分离，也有助于提高ZnTe纳米结构的稳定性。采用超快激光光谱、ESR、XPS和AES 等多种手段研究材料的光激发电子-空穴对的分离、转移等动力学特征，并跟踪监测CO2光还原反应过程, 以期对反应机理进行较为深入的理解, 研究建立材料尺寸-表面结构-电子能级-催化活性等理论关系；揭示光催化剂性能与结构之间的内在联系，阐明光催化转化CO2反应机理；为构建活性高、稳定性好的可见光响应复合纳米光催化系统提供理论和实验依据。

The hybrid nanostructures to be developed are core/shell nanoparticles that have a semiconductor core and a metal oxide shell, linked to a metallic nanoparticle catalyst. Examples include ZnTe/TiO2 core/shell linked to Cu catalyst. The semiconductor core/shell nanostructure serves for initial photo-induced charge separation, while the metallic component provides catalytic sites for subsequent chemical conversion. By taking the advantage of high reducing ability of photo-generated electrons as a result of the very negative conduction bands of ZnTe, one may modify the mechanism and products of the reaction, leading to the formation of higher hydrocarbons (e.g., ethylene & propylene) in high yields. Coating the nanoparticle surface with a metal oxide (e.g., TiO2) shell will not only protect the nanoparticles from dissolution during the photoreaction, but also facilitate charge separation by forming a barrier for controlling back electron transfer. The proposed work will begin with controllable synthesis of hybrid nanostructures using wet-chemical methods. Their structures, morphology and compositions will be characterized using XRD, neutron diffraction, SEM, and TEM. Then, transient visible-pump/visible probe and EPR spectroscopes will be used to measure the charge separation and transfer properties. Photo-reduction of CO2 will be performed in a photo-electrochemical cell and be monitored by analyzing the residual gas samples with a gas chromatograph.