具有不同暴露晶面铈基催化剂对“CO+NO”催化反应机理的准原位光电子能谱和原位红外研究

The emission of nitrogen oxide from both mobile and stationary sources is a serious environmental problem, thus, catalytic decomposition of nitrogen oxide has drawn much attention in catalysis, especially for treating exhaust gases produced under lean-burn and diesel conditions. A number of catalysts have been investigated in the past decades. Among them, catalysts based CuO interacting CeO2 exhibited the promising properties in term of the activity and selectivity. .The particular ability of this class catalysts for CO oxidation or related processes (NO reduction, WGS reaction) were essentially attributed to the synergistic effects produced upon formation of copper oxide-ceria interfacial sites. It was generally accepted that the properties of copper oxide apparently depended on their dispersion degree and/or associated the complex interaction with ceria. In this sense, interests were focused on the investigation of their morphology and structure, surface-active species, preparation method and redox behaviors. To the best of our knowledge, fewer was known for CuO/CeO2 nanocomposites with respect to the shape/crystal plane effects of ceria on the copper species' coordinated environment and activity as highly active catalysts for NO reduction by CO. A careful investigation of the reported strong mental-support interaction through surface structural studies may provide further mechanistic insights into this sensitive model reaction. Herein, in this project, uniform CeO2 morphologies of different exposed crystallographic facets are selectively prepared, and these resultant catalysts are characterized by several analytical techniques, especially in situ FTIR and quasi situ XPS. Attention has been focused on: (1) the relationship between the morphology and the exposed crystallographic facets of CeO2, (2) explore the interaction between copper oxide and these synthesized CeO2 carriers, (3) investigate the interaction of CO or/and NO with these catalysts, and (4) the changes in the surface of these catalysts (valence state and oxygen species, etc.) after interaction with CO or/and NO. The main aims are to obtain a better understanding of the activity correlations with the shape and crystal plane of nanoscale ceria as a support for the dispersed copper species and provide the basis of reference for the development and design of economical and practical exhaust treatment catalysts.

铜铈催化剂被认为在替代贵金属催化剂应用于汽车尾气催化净化方面有巨大前景。本项目拟合成不同暴露晶面的CeO2，并制备CuO/CeO2"模型催化剂"。主要是利用准原位光电子能谱（quasi situ XPS）和原位红外（in situ FTIR）的互补性，结合"CO+NO"模型反应，从催化剂的表面物种变化入手，系统研究（1）CeO2形貌和暴露晶面的关系；（2）负载的铜物种在CeO2不同暴露晶面的存在状态；（3）反应物小分子（CO、NO）在不同暴露晶面CeO2和CuO/CeO2表面的吸附状态；（4）吸附反应物小分子后，CeO2和CuO/CeO2表面相应的变化（价态、氧物种等），构建"载体表面结构-负载活性物种-反应物分子"之间相互作用的内在关系，深入理解CuO/CeO2催化消除CO、 NO的催化作用机理，为开发设计经济实用的尾气净化催化剂提供相关的基础参考。

通过本项目的实施，发展了具有不同暴露晶面CeO2, Ti2O, Cu2O纳米晶及其相关复合材料的制备方法。同时，我们运用多种原位技术手段（in situ FT-IR），及准原位光电子能谱（ex-situ XPS）等，结合模型催化反应（CO+O2, NO+CO, NH3-SCR），探索CO、NO 等分子(以及其他污气体分子存在时)与所制备材料的作用机制，从分子层面上探讨CO、NO 分子及多组份污染物分子在所制备氧化物材料表面的吸附-催化-脱附过程的规律及反应机理，尝试建立了“表面结构—活性物种—反应物分子”之间相互作用的关系，为相关催化剂的研发提供了基础理论支持。同时，我们将这种研究思路拓展到环境光催化领域，阐述了晶面效应对于光催化反应中，光生空穴以及光生电子分离与传输的影响规律，使我们认识到晶面效应在光催化反应中的重要作用。上述研究将为开发设计经济实用的环境催化剂提供相关的基础参考。