催化学报

催化学报 ›› 2020, Vol. 41 ›› Issue (6): 1017-1027.DOI: 10.1016/S1872-2067(20)63533-1

• 论文 • 上一篇    

CO氧化反应中的二氧化铈晶面效应

昂美玉, 王伟伟, 严涵, 卫帅, 贾春江   

  1. 山东大学化学与化工学院胶体与界面化学教育部重点实验室, 特种功能聚集体材料教育部重点实验室, 山东济南 250100
  • 收稿日期:2019-10-30 修回日期:2019-12-17 出版日期:2020-06-18 发布日期:2020-01-21
  • 通讯作者: 王伟伟, 贾春江
  • 基金资助:
    国家自然科学基金（21622106，21771117，21805167）；山东省自然科学基金（JQ201703，ZR2018BB010）；山东省泰山学者计划；山东大学青年学者未来计划（11190089964158）.

Insights into facet-dependent reactivity of CuO-CeO2 nanocubes and nanorods as catalysts for CO oxidation reaction

Yu Aung May, Wei-Wei Wang, Han Yan, Shuai Wei, Chun-Jiang Jia   

  1. Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, Key Laboratory of Special Aggregated Materials, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, Shandong, China
  • Received:2019-10-30 Revised:2019-12-17 Online:2020-06-18 Published:2020-01-21
  • Contact: 10.1016/S1872-2067(20)63533-1
  • Supported by:
    This work was financially supported by the Excellent Young Scientists Fund from National Natural Science Foundation of China (NSFC) (21622106), other projects from the NSFC (grant no. 21805167 and 21771117), the Outstanding Scholar Fund from the Science Foundation of Shandong Province of China (JQ201703), the Doctoral Fund (ZR2018BB010) from the Science Foundation of Shandong Province of China, the Taishan Scholar Project of Shandong Province of China, and the Future Program for Young Scholar of Shandong University. We thank the Center of Structural Characterizations and Property Measurements at Shandong University for help with sample characterizations.

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摘要： 二氧化铈（CeO2）因其具有较强的储放氧能力，被用作氧化还原反应的催化材料.自2005年，研究者制备出形貌可控的CeO2纳米棒、纳米立方块和纳米多面体，在CeO2形貌控制及构效关系研究方面取得长足发展.各种结构表征手段包括原位拉曼（in situ Raman）、原位傅里叶变换红外光谱（in situ DRIFTS）、核磁共振（NMR）和电镜等被用来研究不同形貌CeO2的表面结构和在催化反应中的活性差异.一般的活性规律为CeO2纳米棒（{110}/{100}） > 纳米立方块（{100}） > 纳米多面体（{111}/{100}）.
近年来，负载型CeO2催化剂因其能稳定分散金属，通过金属-载体相互作用调控界面电子结构并表现出优异的催化活性而引起广泛关注，其中晶面效应在负载型CeO2催化体系中显得较为复杂.铜铈催化剂被认为是非常经济有效的CO氧化催化剂，然而由于制备和测试条件差异导致的CeO2晶面对铜铈催化剂催化CO氧化活性的影响规律并不统一.我们之前的研究工作发现纳米棒CeO2-{110}晶面上的Cu-[Ox]-Ce结构不利于形成Cu（I），而纳米颗粒CeO2-{111}晶面上的CuOx团簇很容易形成Cu（I），从而对CO催化氧化极为有利，这与纯载体CeO2的规律并不一致.与此同时，对于铜负载的CeO2纳米棒（NR）及纳米立方体（NC）所体现的性质及活性差异缺少系统深入的研究.
在上述工作基础上，我们采用沉积沉淀法在CeO2NR及CeO2NC上负载1% wt的铜分别得到1CuCe NR和1CuCe NC，并对所合成催化剂的结构和吸附性能进行了表征.高分辨透射电镜（HRTEM）照片显示，CeO2纳米棒主要暴露{110}晶面，而CeO2纳米立方体以{100}晶面为主.催化测试结果表明，1CuCe NC在130 ℃时CO已完全转化为CO2，而相同温度下1CuCe NR只有50%转化.进一步通过氢气程序升温还原（H2-TPR）和一氧化碳程序升温脱附（CO-TPD）分析发现，1CuCe NC催化剂具有较强的还原性且表面氧物种含量高.此外，X射线光电子能谱（XPS）和in situ DRIFTS研究表明，1CuCe NC促进Cu（I）位点生成，导致活性Cu（I）-CO物种增多，这些优异的化学性质导致其具有较高的催化CO氧化活性.

关键词: CuO-CeO2催化剂, 晶面效应, CO催化氧化, 氧化还原性质, 活性位

Abstract: Copper-ceria (CuO-CeO2) catalysts have been known to be very effective for the oxidation of CO, and their chemical behavior has been extensively studied during the last decades. However, the effect of different CeO2 crystal surfaces on the catalytic activity of CuO-CeO2 for the oxidation of CO is still unclear and should be further elucidated. In this study, we deposited 1 wt% Cu on mostly {100}-exposed CeO2 nanocubes (1CuCe NC) and mostly {110}-exposed CeO2 nanorods (1CuCe NR), respectively. Both 1CuCe NC and 1CuCe NR have been used as catalysts for the oxidation of CO and achieved 100% and 50% CO conversion at 130℃, respectively. The differences in the catalytic activity of 1CuCe NC and 1CuCe NR were analyzed using temperature-programmed reduction of H2 and temperature-programmed desorption of CO techniques. The results confirmed the excellent reducibility of the 1CuCe NC catalyst, which was attributed to the weak interactions between Cu and the CeO2 support. Moreover, in situ diffuse reflectance infrared Fourier-transform spectroscopy studies indicated that the {100} planes of 1CuCe NC facilitated the generation of active Cu(I)sites, which resulted in the formation of highly reactive Cu(I)-CO species during the oxidation of CO. Both the excellent redox properties and effective CO adsorption capacity of the 1CuCe NC catalyst increased its catalytic reactivity.

Key words: Copper-ceria catalyst, Crystal facets, CO oxidation, Redox property, Active site