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学科主题: 物理化学
题名: Fascinations of selective oxidation over nano-silver catalysts
作者: Bao XH(包信和)
会议名称: International Symoposium on creation and Control of Advanced Delective Catalysis
会议日期: 2008-7-8
出版日期: 2008-07-08
会议地点: 日本
通讯作者: Xinhe Bao
部门归属: 五室
主办者: 京都大学
摘要: Metallic silver, being differ from the most of the transition metals, characterizes only weak interaction with oxygen, and no obvious adsorption and dissociation of di-oxygen on the surfaces of bulk silvers have been observed at the elevated temperatures. As the excellent catalysts, however, silver has been used extensively in several very important catalytic processes, such as epoxidation of ethylene to ethylene oxide, partial oxidation of methanol to formaldehyde, partial oxidation of benzyl alcohols and catalytic oxidation of CO. The unique activity and selectivity in such the oxygen-related catalytic reactions have been attributed currently to the existence of a subsurface oxygen species, labelled as Oγ, in the toplayers of silvers. Our previous experiments1),2) showed that compared to the “normal” adsorbed atomic oxygen forming on silver surface at low temperature, the Oγ species presents the quite different properties in the respects of the electron and structure as well as the thermal-stability. Such the oxygen species, however, was found to be created on the ordered Ag(111) surface only at the temperature being higher than 500℃ and also an existence of oxygen atmosphere, under which conditions a actual reconstruction with (26x1) superstructure was formed simultaneously. Subsequent theoretical investigations with DFT methods confirmed that the reconstruction of the surface atoms lowers the energy barrier of oxygen diffusion into the bulk of silver, which essentially accelerates the formation of the subsurface oxygen (Oγ). In this report, a unique dependence of the formation of Oγ species on the size of silver particles will be presented, with emphasis on the so-called “nano-effects”. Experimental and theoretical3),4) results show that the temperature for building Oγ in the silver particles could be reduced distinctly with the decrease of the particle size, and such the selective oxygen species can even be observed at room temperature in the system with silver particles in the diameters of 2~4nm, which is fully supported by a recent observation of HRTEM5) upon the formation of Oγ species on the SiO2-supported silver particles. The effects of the enhanced formation of Oγ species in the nano-silver systems on the selective oxidations will be discussed, and the experimental results referring to the selective oxidation of methane, methanol and carbon monoxide at lower temperatures on nano-silver catalysts will be presented as well in this report.
语种: 中文
内容类型: 会议论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/112904
Appears in Collections:中国科学院大连化学物理研究所_会议论文

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Recommended Citation:
Bao XH. Fascinations of selective oxidation over nano-silver catalysts[C]. 见:International Symoposium on creation and Control of Advanced Delective Catalysis. 日本. 2008-7-8.
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