稀土金属/氧化铝模型催化剂的制备及其表面吸附和反应的原位同步辐射研究

Rare-earth metals and their compounds have been widely used as catalyst support or promoter added to catalysts in industry because of their excellent catalytic properties. In this project, we will focus on the exploration of the relationship between the structure and activity of rare-earth metal/oxide catalyst and the development of in-situ synchrotron-radiation techniques for the characterization of catalyst. Using synchrotron radiation photoemission spectroscopy (SRPES) and near-edge X-ray absorption fine structure (NEXAFS) and other surface science techniques, the surface structure of rare-earth metal/Al2O3 catalyst as well as the adsorption and reaction of probing molecules (such as CO,NO and CH4) on the catalyst surface will be comprehensively investigated. In detail, we will mainly address on the following issues: (1) the adsorption site and type (molecular adsorption or dissociative adsorption) of probing molecules on the surface of different rare-earth metal/Al2O3 catalysts, and the nature of the chemical bonding between probing molecules and the surface; (2) the change of morphology and chemical properties on the surface and interface of rare-earth metal/Al2O3 induced by the adsorption of probing molecules; (3) the influence of synergistic effect on the adsorption and reaction of the probing molecules caused by the size of rare-earth metal nanoparticles; (4) the chemical reaction and reaction product during the annealing process for probing molecules adsorbed on the surface of rare-earth metal/Al2O3 at room temperature or lower temperature; (5) In combination with the theoretical calculations on the same systems, we attempt to gain a deeper insight into the mechanism and process of the adsorption and reaction of probing molecules on the surface of rare-earth metal/Al2O3 catalysts and other important information.

稀土金属及其化合物作为催化剂载体或者助剂在众多反应中表现出极为优异的催化性能而在工业中获得广泛应用。本项目着眼于探索稀土/氧化物催化剂的构效关系，发展同步辐射原位催化剂表征技术，利用同步辐射光电子能谱（SRPES）和近边X射线吸收精细结构（NEXAFS）等表征手段，开展稀土金属/Al2O3催化剂的表面结构以及探针分子（CO、NO、CH4等）在其表面的吸附和反应研究。测定探针分子在不同稀土金属/Al2O3表面的吸附类型（分子吸附或解离吸附）、吸附位置和表面键合的化学键的本质；考察吸附引起的催化剂表面和界面形貌和化学性质的变化；研究不同尺寸的稀土金属纳米粒子对探针分子吸附和反应的协同作用；研究在室温或者低温条件下吸附的探针分子在催化剂表面升温过程中的化学变化，并表征反应产物。结合理论计算，获得稀土金属/Al2O3催化剂表面分子吸附和反应产生的机理与过程以及催化剂的构效关系等重要信息。

氧化物担载的稀土金属及贵金属催化剂及在工业中应用广泛，其中金属与氧化物相互作用的强弱、金属在氧化物上的形貌、价态和电子结构等表界面特性是直接影响催化剂活性、选择性及寿命的重要因素。利用本基金项目的资助，我们运用同步辐射技术结合多种表面科学研究手段如扫描隧道显微镜（STM）和低能电子衍射（LEED）等，通过模型催化剂的方式，选择目前在能源和环境领域中广泛应用的CeO2、 ZrO2和Al2O3等氧化物为研究对象，系统地研究了金属Ni、Ag在ZrO2薄膜表面，Ag、Zr在CeO2薄膜表面以及稀土Sm在Al2O3薄膜表面的生长、形貌、电子结构以及热稳定性等。同时考察了探针分子在模型催化剂表面上的吸附和反应，包括O2在Sm/Al2O3模型表面上的吸附和反应。