Hostname: page-component-8448b6f56d-qsmjn Total loading time: 0 Render date: 2024-04-19T08:17:33.981Z Has data issue: false hasContentIssue false
  • English
  • Français

Behavior of Au Species in Au/Fe2O3 Catalysts Characterized by Novel In Situ Heating Techniques and Aberration-Corrected STEM Imaging

Published online by Cambridge University Press:  22 June 2010

Lawrence F. Allard ,
Maria Flytzani-Stephanopoulos  and
Steven H. Overbury
Lawrence F. Allard*
Affiliation:
Physical Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
Maria Flytzani-Stephanopoulos
Affiliation:
Department of Chemical and Biological Engineering, Tufts University, Medford, MA 02155, USA
Steven H. Overbury
Affiliation:
Physical Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
*
Corresponding author. E-mail: allardLFjr@ornl.gov
Get access

Abstract

The recent advent of a novel design of in situ heating technology for electron microscopes has permitted unprecedented control of elevated temperature studies of catalytic materials, particularly when coupled with the sub-Ångström imaging performance of a modern aberration-corrected scanning transmission electron microscope (STEM). Using micro-electro-mechanical-systems (MEMS)-based Aduro™ heating chips from Protochips, Inc. (Raleigh, NC, USA) allows nearly instantaneous heating and cooling of catalyst powders, avoiding effects of temperature ramping as experienced with standard heating stages. The heating technology also provides stable operation limited only by the inherent drift in the microscope stage, thus allowing full image resolution to be achieved even at elevated temperatures. The present study details the use of both the high X-Y spatial resolution in both dark-field and simultaneous bright-field imaging, along with the high resolution in Z (depth sectioning) provided by the large probe incidence semiangle in the aberration-corrected instrument, to characterize the evolution of microstructure in a commercial Au/Fe2O3 water-gas shift catalyst during elevated temperature treatment. The phenomenon of Au diffusion to the surface of hematite support particles to form discrete crystalline Au nanoparticles in the 1–2 nm size range, after a prior leaching treatment to remove surface Au species has been characterized.

Keywords

STEMaberration correctionin situAu catalystsdepth sectioningHAADF
Type
Special Section—Aberration-Corrected Electron Microscopy
Information
Microscopy and Microanalysis , Volume 16 , Issue 4 , August 2010 , pp. 375 - 385
Copyright
Copyright © Microscopy Society of America 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Allard, L.F., Bigelow, W.C., Jose-Yacaman, M., Nackashi, D.P., Damiano, J. & Mick, S.E. (2009a). A new MEMS-based system for ultra-high-resolution imaging at elevated temperatures. Microsc Res Technique 72(3), 208–215.CrossRefGoogle ScholarPubMed
Allard, L.F., Bigelow, W.C., Nackashi, D., Damiano, J. & Mick, S.E. (2008). A new paradigm for ultra-high-resolution imaging at elevated temperatures. Microsc Microanal 14(S2), 792–793.CrossRefGoogle Scholar
Allard, L.F., Borisevich, A., Deng, W., Si, R., Flytzani-Stephanopoulos, M. & Overbury, S.H. (2009b). Evolution of gold structure during thermal treatment of Au/FeOx catalysts revealed by aberration-corrected electron microscopy. J Electron Microsc (Tokyo) 58(3), 199–212.CrossRefGoogle ScholarPubMed
Blake, R.L., Hessevick, R.E., Zoltai, T. & Finger, L.W. (1966). Refinement of the hematite structure. Amer Mineral 51, 123–129.Google Scholar
Blom, D.A., Allard, L.F., Mishina, S. & O'Keefe, M.A. (2006). Early results from an aberration-corrected JEOL 2200FS STEM/TEM at Oak Ridge National Laboratory. Microsc Microanal 12, 483–491.CrossRefGoogle ScholarPubMed
Borisevich, A.Y., Lupini, A.R., Koschan, A.F., Mercimek, M., Abidi, M.A. & Pennycook, S.J. (2008). 3D Scanning transmission electron microscopy for catalysts: Imaging and data analysis. Microsc Microanal 14(S2), 168–169.CrossRefGoogle Scholar
Borisevich, A.Y., Lupini, A.R. & Pennycook, S.J. (2006a). Depth sectioning with the aberration-corrected scanning transmission electron microscope. Proceeding of the National Academy of Sciences 103(9), 3044–3048.CrossRefGoogle ScholarPubMed
Borisevich, A.Y., Lupini, A.R., Travaglini, S. & Pennycook, S.J. (2006b). Depth sectioning of aligned crystals with the aberration-corrected scanning transmission electron microscope. J Electron Microsc (Tokyo) 55(1), 7–12.CrossRefGoogle Scholar
Buffat, P. & Borel, J.-P. (1976). Size effect on the melting temperature of gold particles. Phys Rev A 13(6), 2287–2298.CrossRefGoogle Scholar
De Jonge, N., Sougrat, R., Northan, B.M. & Pennycook, S.J. (2010). Three-dimensional scanning transmission electron microscopy of biological specimens. Microsc Microanal 16, 53–62.Google ScholarPubMed
Deng, W., Carpenter, C., Yi, N. & Flytzani-Stephanopoulos, M. (2007). Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions. Topics in Catalysis 44(1–2), 199–208.CrossRefGoogle Scholar
Howe, J.Y., Allard, L.F., Bigelow, W.C. & Overbury, S.H. (2010). Synergy of combined (S)TEM imaging techniques for the characterization of catalyst behavior during in-situ heating. Microsc Microanal 16(S2), 312–313.CrossRefGoogle Scholar
Pennycook, S.J., Chisholm, M.F., Lupini, A.R., Varela, M., van Benthem, K., Borisevich, A.Y., Oxley, M.P., Luo, W. & Pantelides, S.T. (2008). Materials applications of aberration-corrected STEM. In Advances in Imaging and Electron Physics, Hawkes, P.W. (Ed.), 153, pp. 339–340. San Diego, CA: Elsevier Inc.Google Scholar
Rashkeev, S.N., Lupini, A.R., Overbury, S.H., Pennycook, S.J. & Pantelides, S.T. (2007). Role of the nanoscale in catalytic CO oxidation by supported Au and Pt nanostructures. Phys Rev B 76, 035438–035443.CrossRefGoogle Scholar
Sun, J. (2002). A model for shrinkage of a spherical void in the center of a grain: Influence of lattice diffusion. J Mater Eng Perf 11(3), 322–330.CrossRefGoogle Scholar
Takahashi, Y., Ueno, F. & Nishiguchi, K. (1988). A numerical analysis of the void-shrinkage process controlled by surface diffusion. Acta Metall 36(11), 3007–3018.CrossRefGoogle Scholar
van Benthem, K., Lupini, A.R., Kim, M., Baik, H.S., Doh, S.J., Lee, J.H., Oxley, M.P., Findlay, S.D., Allen, L.J. & Pennycook, S.J. (2005). Three-dimensional imaging of individual hafnium atoms inside a semiconductor device. Appl Phys Lett 87, 034104-1–034104-3.CrossRefGoogle Scholar
Wang, H. & Li, Z. (2004). The three-dimensional analysis for diffusive shrinkage of a grain-boundary void in stressed solid. J Mater Sci 39, 3425–3432.CrossRefGoogle Scholar
Xin, X., Intaraprasonk, V. & Muller, D.A. (2008). Depth sectioning of individual dopant atoms with aberration-corrected scanning transmission electron microscopy. Appl Phys Lett 92(1), 013125.CrossRefGoogle Scholar
Xin, X.L. & Muller, D.A. (2009). Aberration-corrected ADF-STEM depth sectioning and prospects for reliable 3D imaging in S/TEM. J Elect Microsc (Tokyo) 58(3), 157–165.CrossRefGoogle ScholarPubMed