催化学报

催化学报 ›› 2020, Vol. 41 ›› Issue (9): 1360-1368.DOI: 10.1016/S1872-2067(20)63564-1

• 论文 • 上一篇    下一篇

CeO2/Pt(111)反向催化剂结构和活性的密度泛函理论研究

郑珠媛a, 王栋a, 张毅b, 杨帆b, 龚学庆a   

  1. a 华东理工大学化学与分子工程学院, 计算化学中心, 工业催化研究所, 结构可控先进功能材料及其制备教育部重点实验室, 上海 200237;
    b 中国科学院大连化学物理研究所, 能源材料化学协同创新中心, 催化基础国家重点实验室, 辽宁大连 116023
  • 收稿日期:2020-01-09 修回日期:2020-02-23 出版日期:2020-09-18 发布日期:2020-08-08
  • 通讯作者: 王栋, 龚学庆
  • 基金资助:
    国家重点研发计划（2018YFA0208602）；国家自然科学基金（21825301，21573067，21421004，21903025）；上海市学术研究负责人计划（17XD1401400）.

Structures and reactivities of the CeO2/Pt(111) reverse catalyst: A DFT+U study

Zhu-Yuan Zhenga, Dong Wanga, Yi Zhangb, Fan Yangb, Xue-Qing Gonga   

  1. a Key Laboratory for Advanced Materials, Centre for Computational Chemistry and Research Institute of Industrial Catalysis, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China;
    b State Key Laboratory of Catalysis, Collaborative Innovation Center of Chemistry for Energy Materials, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
  • Received:2020-01-09 Revised:2020-02-23 Online:2020-09-18 Published:2020-08-08
  • Supported by:
    This work was supported by National Key R&D Program of China (2018YFA0208602), National Natural Science Foundation of China (21825301, 21573067, 21421004, 21903025) and Program of Shanghai Academic Research Leader (17XD1401400). The authors also thank the National Super Computing Center in Jinan for the computing time.

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摘要： 铈基材料因其独特的Ce4+/Ce3+转化性质而广泛运用于非均相催化反应中.尽管在实验和理论上对纯净二氧化铈表面的物理和/或化学性质进行了深入研究，但是与二氧化铈有关的界面结构和反应性能引起了人们的极大兴趣.其中，已有报道表明，氧化铈/金属反向催化剂相较于氧化铈、金属或者金属/氧化铈负载材料能明显提高CO催化氧化和水汽转化等反应活性.然而多数前期研究并没有从理论上给出合理解释，同时也并未说明反向催化剂中氧化铈结构（层数）和性质的关系.可以预见，因受到金属基板的影响，二氧化铈表面的物化性质，如氧空位形成能、电子分布、催化活性等必然会发生变化.本文通过库伦作用校正的密度泛函理论（DFT+U）计算，系统地研究了不同厚度的CeO2/Pt（111）反向催化剂几何结构和电子性质，催化CO氧化的性能.本文首先在Pt（111）载体上明确了单层CeO2（111）的最佳结构，然后研究随着二氧化铈厚度增加，各复合结构界面热力学稳定性、几何结构和电荷性质的变化.
计算结果表明：首先，单层CeO2/Pt（111）比双层和三层CeO2/Pt（111）复合结构在界面处表现出更强的相互作用，并且其强度与界面结合结构密切相关，如界面O-Pt键的数量及其长度等；其次，氧化铈板层和Pt基板之间的接触会显著影响界面处一个氧化铈层和两个金属层内的电子分布，使氧化铈外暴露表面的氧空位形成能降低~0.3eV，而界面氧空位形成能则显著降低1.3-1.8eV，并且当表面上沉积≥ 2个氧化铈层时，氧化铈/铂复合材料的物理性能会趋向收敛；最后，通过计算单层CeO2/Pt（111），单层CeO2和模拟体相结构的三层CeO2（111）表面上的CO氧化过程，结果表明三者均遵循Mvk机理，并且关键步骤OC…Os偶联的反应能垒分别是0.45，0.33和0.61eV，表明三者的活性趋势为ML CeO2 > ML CeO2/Pt（111） > TL CeO2（111）.综合考虑到单层CeO2/Pt（111）界面处适度的二氧化铈-铂相互作用，一方面可以极大提高复合材料热力学稳定性，另一方面还成功保留了单层二氧化铈的优异催化活性，因此单层CeO2/Pt（111）复合材料从理论上认为是一种优异的CO氧化催化剂.

关键词: CeO2/Pt(111)反向催化剂, 界面结构, 氧空位, CO氧化, 密度泛函理论

Abstract: For heterogeneous catalysts, the build-up of interface contacts can influence markedly their activities. Being different from the conventional supported metal/oxide catalysts, the reverse type of oxide/metal structures, e.g. the ceria/Pt composite, have emerged as novel catalytic materials in many fields. However, it remains challenging to determine the optimal interface structure and/or the metal-oxide synergistic effect that can boost catalytic activities. In this work, we conducted density functional theory calculations with on-site Coulomb interaction correction to determine the optimal structures and investigate the physical as well as catalytic properties of various CeO2/Pt(111) composites containing CeO2(111) monolayer, bilayer, and trilayer at Pt(111). We found that the interaction strength between CeO2(111) and Pt(111) substrate first reduces as the ceria slab grows from monolayer to bilayer, and then largely gets converged when the trilayer occurs. Such trend was well rationalized by analyzing the number and distances of O-Pt bonds at the interface. Calculated Bader charges uncovered the significant charge redistribution occurring around the interface, whereas the net electron transfer across the interface is non-significant and decreases as ceria thickness increases. Moreover, comparative calculations on oxygen vacancy formation energies clarified that oxygen removal can be promoted on the CeO2/Pt(111) composites, especially at the interface. We finally employed CO oxidation as a model reaction to probe the surface reactivity, and determined an intrinsic activity order of monolayer CeO2(111) > monolayer CeO2(111)/Pt(111) > regular CeO2(111). More importantly, we emphasized the significant role of the moderate ceria-Pt interaction at the interface that endows the CeO2/Pt reverse catalyst both good thermostability and high catalytic activity. The monolayer CeO2(111)/Pt(111) composite was theoretically predicted highly efficient for catalyzing CO oxidation.

Key words: CeO2/Pt reverse catalyst, Interface structure, Oxygen vacancy, CO oxidation, Density functional theory