Ag基催化剂中Ag的尺寸效应及其对机动车尾气氨净化的影响机制研究

环境中的氨（NH3）污染可以促进大气中二次粒子的形成，是灰霾污染的重要成因。因此，机动车尾气中的NH3逃逸问题日益得到重视，高效氨氧化催化剂（AOC）的开发迫在眉睫。现有AOC催化剂存在操作温度高、易水中毒等问题，难以满足机动车尾气NH3排放要求。本研究以NH3-SCO活性较高的Ag基催化剂为研究对象，在Ag单原子催化剂的基础上，采用定向还原的方式调控H2还原温度、时间等条件，使单原子Ag逐级团聚从而制备出载有不同粒径Ag0的Ag/Al2O3催化剂，进而通过Ag0尺寸效应的揭示开发高活性及N2选择性的Ag基催化剂；然后通过H2O中毒机制的探究，拟采用疏水处理与酸改性结合的方式优化催化剂的抗水性；最终通过反应机理及构效关系的阐明进一步指导催化剂的设计，从而开发出符合机动车尾气应用条件的AOC催化剂。本项目将为AOC催化剂的开发及优化提供理论依据，对基础研究和技术应用方面均有重要价值。

Ammonia (NH3) pollution in the environment will promote the formation of secondary particles in the atmosphere and thus is an important factor for the formation of haze pollution. Therefore, the problem of NH3 slip in vehicle exhaust has been aroused attention very recently. The emission limit of NH3 (10 ppm) was added in the newly promulgated National VI emission standard, and the development of an efficient ammonia oxidation catalyst (AOC) is imminent. There are many insufficiencies in the existing AOC catalysts, such as high operating temperature, poor N2 selectivity, and easy poisoning from H2O, and thus it is difficult to meet the NH3 emission requirements of automobile exhaust. In this study, Ag-based catalysts, which possess high NH3-SCO activity at low temperature, were investigated on the basis of the Ag single-atom catalyst Ag/nano-Al2O3 developed before. Ag/Al2O3 catalysts loading Ag0 with different particle sizes were prepared by adjusting the H2 reduction conditions directionally, such as reduction temperature and time, to make Ag atomic aggregate gradually. And thus Ag-based catalysts with high activity and N2 selectivity will be developed by revealing the size effect mechanism of Ag0 on NH3-SCO reaction. Then through the exploration of H2O poisoning mechanism, the water resistance of the catalyst will be optimized by combining hydrophobic treatment and acid modification. Finally, the design of the catalyst is further guided by the exploration of the reaction mechanism and structure-activity relationship, so as to develop an AOC catalyst that meets the application conditions of automobile exhaust. This project will provide a theoretical basis for the development and optimization of AOC catalysts, and is of both fundamental and technical importance.