氧化物负载的金属单原子催化剂的结构和性能研究：从模型催化到实际催化

In recent years, single-atom catalysts (SACs) become a hot topic in catalysis and have attracted extensive attention due to their outstanding activities and stabilities. Understanding the relationship between the structures and properties as well as the catalytic mechanisms of SACs is essential for the design of new SACs and the improvement in the performance and stability of known SACs. It has been demonstrated in many cases that oxide-supported metal single atom catalysts display exceptional catalytic properties in heterogeneous catalysis. In this proposal, we plan to study the SACs first through the approach of so-called "model catalysis" using advanced surface science techniques and then design and synthesize the real catalysts. In detail, we will first prepare the oxide (ceria and cobalt oxides)-supported SACs (Pt, Pd and Au) on ordered oxide thin films under the controllable conditions in ultrahigh vacuum and in-situ study their surface morphologies, electronic structures and thermal stabilities through multiple synchrotron radiation based spectroscopies together with conventional surface science techniques such as scanning tunneling microscopy. Moreover, the adsorption/reaction process and mechanism of probing molecules like CO,H2O and CH4 on the surfaces of model catalysts will be investigated. Combined with theoretical calculations, we will gain deep fundamental understandings of the intrinsic relationship between the structures and catalytic properties of oxide-supported SACs at the atomic-molecular level. On the basis of the knowledge gained from these model catalysts, we will try to design and prepare real oxide-supported SACs and test their catalytic performances in some reactions such as CO oxidation.

近年来，单原子催化剂因其特有的活性和稳定性成为催化领域的一个研究热点，理解单原子催化的基本机理对于设计高性能和高稳定性的催化剂体系至关重要。已有研究相继证明，氧化物负载的贵金属单原子催化剂在一些多相催化反应中具有很高的催化活性。本项目将模型催化与实际催化相结合，以单原子催化为切入点，拟采用表面科学方法，首先通过“模型催化”的方式在真空中可控制备氧化物负载的金属单原子模型催化剂；利用多种同步辐射软X射线谱学技术结合扫描隧道显微镜等表面分析手段，原位研究氧化铈和氧化钴负载金属（Pt、Pd和Au）单原子催化剂的表面形貌、电子结构和热稳定性；研究CO、H2O和甲烷等探针分子在催化剂表面的化学吸附及反应的过程和机理。结合理论计算，从原子-分子水平揭示氧化物负载金属单原子催化剂的结构与性能之间的内在联系。并依据这些结果，精确设计并制备氧化物负载单原子实际催化剂，测试其在CO氧化等反应中的催化性能。

单原子催化剂因其特有的活性和稳定性成为催化领域的一个研究热点，因而理解单原子催化的基本原理对于设计高性能和高稳定性的催化剂体系至关重要。本项目将模型催化和实际催化相结合，首先开展了氧化铈和氧化钴负载的金属纳米颗粒和单原子模型催化剂的制备，利用同步辐射光电子能谱（SRPES）和超高真空扫描隧道显微镜（STM）对其进行结构和热稳定性的研究，并利用SRPES、STM、低能电子衍射（LEED）、超高真空红外（IRAS）和程序升温脱附（TPD）技术研究了各种探针分子（CO、NO）在模型催化剂表面的吸附和反应过程，以探索催化剂表面催化反应的机制；进而指导合成氧化物负载的金属纳米颗粒和金属单原子实际催化剂，通过球差校正电镜（HAADF-STEM）和X射线吸收精细结构谱（XAFS）证实了孤立原子的存在形式，并研究催化剂在一定条件下的催化活性和选择性；为设计具有特定功能的以氧化物为载体的金属纳米颗粒和金属单原子催化剂体系提供了思路。