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Evolution of gold structure during thermal treatment of Au/FeOx catalysts revealed by aberration-corrected electron microscopy.

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Title: Evolution of gold structure during thermal treatment of Au/FeOx catalysts revealed by aberration-corrected electron microscopy.
Authors: Lawrence F. Allard, Albina Borisevich, Weiling Deng, Rui Si, Maria Flytzani-Stephanopoulos, Steven H. Overbury
Source: Journal of Electron Microscopy. Jun2009, Vol. 58 Issue 3, p199-199. 1p.
Subjects: Optical aberrations, Electron microscopy, Imaging systems, Research
Abstract: High-resolution aberration-corrected electron microscopy was performed on a series of catalysts derived from a parent material, 2 at.% Au/Fe2O3 (WGC ref. no. 60C), prepared by co-precipitation and calcined in air at 400°C, and a catalyst prepared by leaching surface gold from the parent catalyst and exposed to various treatments, including use in the water–gas shift reaction at 250°C. Aberration-corrected JEOL 2200FS (JEOL USA, Peabody, MA) and Vacuum Generators HB-603U STEM instruments were used to image fresh, reduced, leached, used and re-oxidized catalyst samples. A new in situ heating technology (Protochips Inc., Raleigh, NC, USA), which permits full sub-Ångström imaging resolution in the JEOL 2200FS was used to study the effects of temperature on the behavior of gold species. A remarkable stability of gold to redox treatments up to 400°C, with atomic gold decorating step surfaces of iron oxide was identified. On heating the samples in vacuum to 700°C, it was found that monodispersed gold began to sinter to form nanoparticles above 500°C. Gold species internal to the iron oxide support material was shown to diffuse to the surface at elevated temperature, coalescing into discrete nanocrystals. The results demonstrate the value of in situ heating for understanding morphological changes in the catalyst with elevated temperature treatments. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Electron Microscopy is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Evolution of gold structure during thermal treatment of Au/FeOx catalysts revealed by aberration-corrected electron microscopy.
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  Data: <searchLink fieldCode="AR" term="%22Lawrence+F%2E+Allard%22">Lawrence F. Allard</searchLink><br /><searchLink fieldCode="AR" term="%22Albina+Borisevich%22">Albina Borisevich</searchLink><br /><searchLink fieldCode="AR" term="%22Weiling+Deng%22">Weiling Deng</searchLink><br /><searchLink fieldCode="AR" term="%22Rui+Si%22">Rui Si</searchLink><br /><searchLink fieldCode="AR" term="%22Maria+Flytzani-Stephanopoulos%22">Maria Flytzani-Stephanopoulos</searchLink><br /><searchLink fieldCode="AR" term="%22Steven+H%2E+Overbury%22">Steven H. Overbury</searchLink>
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Electron+Microscopy%22">Journal of Electron Microscopy</searchLink>. Jun2009, Vol. 58 Issue 3, p199-199. 1p.
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  Data: High-resolution aberration-corrected electron microscopy was performed on a series of catalysts derived from a parent material, 2 at.% Au/Fe2O3 (WGC ref. no. 60C), prepared by co-precipitation and calcined in air at 400°C, and a catalyst prepared by leaching surface gold from the parent catalyst and exposed to various treatments, including use in the water–gas shift reaction at 250°C. Aberration-corrected JEOL 2200FS (JEOL USA, Peabody, MA) and Vacuum Generators HB-603U STEM instruments were used to image fresh, reduced, leached, used and re-oxidized catalyst samples. A new in situ heating technology (Protochips Inc., Raleigh, NC, USA), which permits full sub-Ångström imaging resolution in the JEOL 2200FS was used to study the effects of temperature on the behavior of gold species. A remarkable stability of gold to redox treatments up to 400°C, with atomic gold decorating step surfaces of iron oxide was identified. On heating the samples in vacuum to 700°C, it was found that monodispersed gold began to sinter to form nanoparticles above 500°C. Gold species internal to the iron oxide support material was shown to diffuse to the surface at elevated temperature, coalescing into discrete nanocrystals. The results demonstrate the value of in situ heating for understanding morphological changes in the catalyst with elevated temperature treatments. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
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  Data: <i>Copyright of Journal of Electron Microscopy is the property of Oxford University Press / USA and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1093/jmicro/dfp016
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        Text: English
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              Text: Jun2009
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              Y: 2009
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