Abstract
High-resolution aberration-corrected electron microscopy was performed on a series of catalysts derived from a parent material, 2 at. AuFe2O3 (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-ngström 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.
Original language | English |
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Pages (from-to) | 199-212 |
Number of pages | 14 |
Journal | Journal of Electron Microscopy |
Volume | 58 |
Issue number | 3 |
DOIs | |
State | Published - Jun 2009 |
Funding
Research sponsored by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC. The High Temperature Materials Laboratory microscopy facility at ORNL is supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, U.S. Department of Energy. Research at Tufts University sponsored by the Office of Basic Energy Sciences, Hydrogen Fuel Initiative Program, grant no. DE-FG02-05ER15730, U.S. Department of Energy.
Keywords
- Aberration-corrected
- Gold
- High-resolution microscopy
- In situ heating
- Iron oxide
- Water-gas shift catalyst