针对水煤气变换反应的铜铈催化剂的界面结构调控和活性位点指认

CuO-CeO2 as one of the typical catalysts for low temperature water gas shift (WGS) reaction has been intensively studied during the last decade. However, due to the structural complexity and the instability of CuO-CeO2 catalyst under WGS conditions, the interfacial structure and detailed mechanism of the catalytic process occurred on the interface of CuO-CeO2 is still to be explored. Therefore, our program aims to achieve the controllable synthesis of Cu-O-Ce solid solution, supported CuO clusters and supported CuO particles catalysts for the WGS reaction, thus gain the structure-activity relationship within a wide range of sizes of CuO species. Combining the synthesis of CuO supported on certain exposed faces of ceria, we would like to explore the reactivity of various hydroxyl species those act as active reactant from the activation of water. Various structural characterizations, especially including X-ray absorption fine structure (XAFS) technique were used to precisely determine the structure and status of the catalysts. To further confirm the reaction between the adsorbed CO and hydroxyl species in the catalyst surface, the temperature programmed surface reaction (TPSR) techniques and the in-situ characterizations including in-situ FTIR and in-situ Raman would be applied. Furthermore, theoretical studies based on DFT calculations will be adopted to reveal the reaction mechanism.

铈基氧化铜催化剂是低温水煤气变换反应的经典催化剂，由于CuO与CeO2之间的复杂相互作用以及反应条件下的结构变化，对于铜铈催化剂活性位点的认识仍亟待深入，尤其缺乏对于不同界面结构的CuO-CeO2催化剂性能的系统考察，对于催化剂表面活性羟基物种参与反应的机理也认识不足。因此，本项目拟在实现Cu-O-Ce固溶体、CeO2负载的CuO团簇、CeO2负载的CuO纳米颗粒三种不同界面结构的催化剂可控制备的基础上，系统考察广泛尺寸范围的铜物种的铜铈催化剂的催化行为；进一步选择具有固定晶面的CeO2载体，构建具有不同配位结构的表面羟基，考察其作为活性氧物种的反应性；同时借助X射线精细结构吸收谱表征催化剂精细结构，使用原位红外和拉曼光谱及程序升温表面反应等技术重点考察不同铜物种及表面空位对于催化剂吸附CO和解离H2O分子的影响，结合理论计算，指认活性位点并深入理解反应机理。

本项目实现了高活性二氧化铈基铜催化剂的可控制备，并对其进行水煤气变换反应研究，揭示了其在反应过程中的本征活性位点及构效关系。本项目取得以下重要成果：在烧结的 CuO/CeO2催化剂中构筑了不饱和配位的高效铜原子（Cu1O3）活性位点，揭示了CeO2表面Cu1O3位点催化反应新机理;在反相 CeO2/Cu催化剂中构建了纳米二氧化铈（2-3 nm）/体相铜（>100 nm）稳定的界面，发展了验证水煤气变换反应机理的有效实验方法；在CuO-CeO2催化剂催化水煤气变换反应中，发现载体CeO2会原位产生氧空位解离H2O以及CeO2晶格氧扩散至表面氧化金属Cu，确保活性位点的稳定和供给。以上研究工作为深刻理解CuO-CeO2催化剂的本质构效关系和拓展其应用提供重要的实验依据和理论基础。