Shape-dependent interplay between oxygen vacancies and Ag-CeO₂ interaction in Ag/CeO₂ catalysts and their influence on the catalytic activity

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• 作者：Sujie Chang ; Mo Li ; Qing Hua ; Lijuan Zhang ; Yunsheng Ma ; Bangjiao Ye ; Weixin Huang
• 关键词：Ag/CeO2 catalysts ; CO oxidation ; Active structure ; Metal&ndash ; support interaction ; Oxygen vacancy ; Shape dependence
• 刊名：Journal of Catalysis
• 出版年：2012
• 出版时间：September, 2012
• 年：2012
• 卷：293
• 期：Complete
• 页码：195-204
• 全文大小：2051 K

文摘

Ag/CeO₂ catalysts employing CeO₂ nanocubes (c-CeO₂) and nanorods (r-CeO₂) as the support were prepared by conventional incipient wetness impregnation followed by calcination at 500 ¡ãC in air. Their structures have been characterized in detail and their catalytic activities in CO oxidation have also been tested. c-CeO₂ and r-CeO₂ nanocrystals exhibit different concentrations and structures of oxygen vacancies. The silver-r-CeO₂ interaction is stronger than the silver-c-CeO₂ interaction. Fine Ag nanoparticles form in 1 % -Ag/c-CeO₂ and grow in size in 3 % -Ag/c-CeO₂; however, positively charged clusters dominate in 1 % -Ag/r-CeO₂, and fine Ag nanoparticles dominate in 3 % -Ag/r-CeO₂. Supported Ag nanoparticles are much more capable of creating oxygen vacancies in CeO₂ than supported positively charged clusters. More oxygen vacancies form in Ag/c-CeO₂ than in Ag/r-CeO₂. The average charge density of oxygen vacancies and the ratio between large oxygen vacancy clusters and small vacancies in CeO₂ nanocrystals are enhanced when loaded with positively charged clusters but reduced when loaded with Ag nanoparticles. Ag nanoparticles greatly promote the reduction and catalytic activity in CO oxidation of CeO₂ nanocrystals but positively charged clusters do not. These results demonstrate the concept that the interplay between oxygen vacancies and Ag-CeO₂ interaction controls the structures of silver and CeO₂ in Ag/CeO₂ catalysts and thus their surface reactivity and catalytic activity, deepening the fundamental understanding of metal/CeO₂ catalysts. These results also reveal that the interplay between oxygen vacancies and Ag-CeO₂ interaction in Ag/CeO₂ catalysts depends on the shape of CeO₂ support, opening up a new strategy for the design of efficient and economic metal/CeO₂ catalysts by engineering the shape of CeO₂ support.