Nanostructural and chemical characterization of supported metal oxide catalysts by aberration corrected analytical electron microscopy

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• 作者：Wu  ; Zhou^a ;   ; ^{wu.zhou@vanderbilt.edu} ; Israel E.  ; Wachs^b ; Christopher J.  ; Kiely^a ;   ; ^b ;   ; ^{chk5@lehigh.edu}
• 关键词：Analytical electron microscopy ; STEM ; HAADF imaging ; EELS ; Catalysis ; Supported metal oxide catalyst ; WO₃ ; ZrO₂ ; TiO₂ ; SiO₂
• 刊名：Current Opinion in Solid State & Materials Science
• 出版年：2012
• 出版时间：February 2012
• 年：2012
• 卷：16
• 期：1
• 页码：10-22
• 全文大小：2557 K

文摘

The performance of catalyst materials are usually governed by the precise atomic structure and composition of very specific catalytically active sites. Therefore, structural and chemical characterization at the atomic scale becomes a vital requirement in order to identify any structure¨Cperformance relationships existing in heterogeneous catalyst systems. Aberration-corrected scanning transmission electron microscopy (STEM) represents an ideal means to probe the atomic scale structural and chemical information via a combination of various imaging and spectroscopy techniques. In particular, high-angle annular dark-field (HAADF) imaging provides directly interpretable atomic number (Z) contrast information; while X-ray energy dispersive spectroscopy (XEDS) and electron energy-loss spectroscopy (EELS) spectrum imaging can be used to identify the chemical composition and oxidation state. Here we review some applications of aberration-corrected STEM to catalyst research, firstly in the context of supported metal catalysts, which serve as ideal material systems to illustrate the power of these techniques. Then we focus our attention on more recent progress relating to the characterization of supported metal oxide catalysts using aberration-corrected STEM. We demonstrate that it is now possible to directly image supported surface oxide species, study oxide wetting characteristics, identify the catalytic active sites and develop new insights into the structure¨Cactivity relationships for complex double supported oxide catalysts. Future possibilities for in situ and gentle low voltage electron microscopy studies of oxide-on-oxide materials are also discussed.