多功能催化材料中不同功能单元的界面交互作用与催化行为研究

Multifunctional catalyst plays a very important role in catalysis. Based on the design of a multifunctional catalyst which owns the catalytic activity for both methane decomposition and selective oxidation of carbon deposition to CO, we proposed a novel two-step method for syngas generation from methane. Our previous researches showed that the interface between different active components in the multifunctional catalysts plays a significant role in the two-step reactions. Therefore, the present proposal focuses on the interface effects between different active components in the multifunctional catalysts. With methane decomposition and carbon deposition selective oxidation as probe reactions, CeO2-Fe2O3, CeO2-Co3O4 and Co3O4-Fe2O3 mixed oxides will be investigated as model catalysts. CeO2, Fe2O3, and Co3O4 crystals with different morphology and exposed crystal planes would be prepared. Such oxides can be assembled to mixed oxides, owning uniform interface between different components. The structural and chemical interactions as well as the size effects in the interface under different preheat conditions are planed to investigate, and the results will be related to the physicochemical properties. The relationship between the structure and catalytic performance of different catalysts will be discussed based on different characterizations. The in situ technologies (e.g., in situ FT-IR and in situ XPS) combining with the density functional theory (DFT) studies will be performed to explore the adsorption sites and possible reaction pathways of reactants on the interface, obtaining the catalytic mechanism. The evolution of the interface in the reaction process will also be detected to understand the dynamic relationship between the interface states and the catalytic activity. After the above researches, the structural and chemical features of the interface between different components in the multifunctional catalysts can be clarified. The nature of the interface effects in catalysis and the interface assembly behaviors between different active components in catalyst preparation will be deeply understood, which will provide useful references for designing new multifunctional catalysts.

催化剂的多功能化是现代催化技术的一个重要发展方向。在青年基金项目“甲烷中低温转化制合成气中可控功能化催化材料的构建及其反应机制”的执行中，我们发现催化剂不同功能单元的界面有重要催化作用且具可调性。基于此，本项目拟以催化过程中多功能催化剂上不同活性组分的界面效应为切入点，以铈铁、铈钴和铁钴三种复合氧化物为模型催化剂，以甲烷裂解和积碳选择性氧化为探针反应，以常规和原位表征技术并结合广义梯度近似的密度泛函理论(DFT+U)计算为研究手段，围绕不同功能粒子的均一化组装、不同功能粒子以不同晶面作用时的结构及化学交互作用和催化反应中界面的微观演变与催化性能的相关性等关键科学问题，探明多功能催化剂中不同功能单元接触界面的结构与化学特征，揭示材料界面特征与催化性能间的内在关联与规律，探究界面参与催化反应的分子机制，获得通过晶面调控和界面组装创制多功能催化剂的基本原理，为新型催化剂设计提供新的重要支撑。

界面效应是多相催化剂中不同组分间协同作用最重要的方式之一。项目以催化剂中不同氧化物间的界面交互作用为主线，通过氧化物的形貌控制改变其暴露晶面，进而组装具有不同类型界面的复合氧化物催化剂。运用各类表征手段系统研究了CeO2-Fe2O3、CeO2-Co2O3和CeO2-LaFeO3等催化剂体系的物理化学性质（如微结构、界面状态、储氧能力和还原能力等）和催化性能。运用原位FTIR/Raman技术，并结合梯度近似（GGA）的密度泛函理论研究了不同催化剂界面氧空位形成机理及甲烷吸附与转化机制，探讨了界面催化的决定性影响因素。主要研究成果有：① 探明了制备不同形貌Fe2O3的关键控制因素，揭示了负载型的CeO2/α-Fe2O3催化剂和固溶体型CeO2-Fe2O3催化材料通过不同类型界面控制其催化活性的本质。② 绘制了不同形貌Co3O4的合成地图，揭示了Co3O4在催化氧化反应中的形貌效应，阐述了CeO2/Co3O4催化剂与甲烷反应及催化氧化中的构效关系。③ 阐明了CeO2-Fe2O3界面氧空位形成机理及甲烷吸附解离路径。④ 发现了三维有序大孔结构有利于优先暴露CeO2（110）晶面的现象，利用原位手段阐明了暴露晶面在催化CO氧化中的决定性作用。⑤ 发现了CeO2与LaFeO3在界面处的强相互作用，在该体系中首次观察到了氢溢流现象，系统阐述了CeO2/LaFeO3催化剂的界面催化机理。项目的实施为通过调控复合催化剂中不同组分的界面交互作用提升催化剂活性和稳定性提供了一定的理论和实践支撑。