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Morphology and structure of CuOx/CeO2 nanocomposite catalysts produced by inert gas condensation: An HREM, EFTEM, XPS, and high-energy diffraction study

Skårman, Björn LU ; Nakayama, T; Grandjean, D; Benfield, RE; Olsson, E; Niihara, K and Wallenberg, Reine LU (2002) In Chemistry of Materials 14(9). p.3686-3699
Abstract
Inert gas condensation (IGC) has been employed to produce nanoparticles of the low-temperature combustion catalyst CuOx/CeO2. For the first time we have used a multiple heating crucible setup to tailor various morphologies over the whole compositional range (2-98% Cu). The factors that control the growth, structure, and morphology of the nanocomposite have been studied. A powerful combination of complementary characterization methods has been used to elucidate the catalytic synergistics of this material. Investigations by high-resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) are supported by X-ray photoelectron spectroscopy (XPS) and high-energy diffraction (HED) measurements. The nonstoichiometric... (More)
Inert gas condensation (IGC) has been employed to produce nanoparticles of the low-temperature combustion catalyst CuOx/CeO2. For the first time we have used a multiple heating crucible setup to tailor various morphologies over the whole compositional range (2-98% Cu). The factors that control the growth, structure, and morphology of the nanocomposite have been studied. A powerful combination of complementary characterization methods has been used to elucidate the catalytic synergistics of this material. Investigations by high-resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) are supported by X-ray photoelectron spectroscopy (XPS) and high-energy diffraction (HED) measurements. The nonstoichiometric CuOx/CeO2 composite displays an amorphous character consisting of aggregated CeO2 (ceria) nanocrystallites over which amorphous copper clusters (or a thin film of a solid solution) are finely dispersed. In the range 6similar to20% Cu, copper is predominantly located at the surface, which can give the material optimum catalytic properties. Development of crust structures, for example, core-shells, are formed in the 30similar to70% Cu concentration range and is attributable to a sequential oxidation of Ce followed by Cu and an ideal proportion of lattice expansion for the oxides. We suggest a model that illustrates the formation of the crust structure and may explain the observed extreme dispersion of copper on ceria. The helium gas pressure during the thermalization controls the crystal size and the degree of crystallite aggregation. Rounded particle shapes consisting of epitaxially interfaced nanocrystallites exhibit an X-ray amorphous character, while block-shaped crystals displaying sharp edges and distinct flat surfaces give rise to a higher X-ray crystallinity. Bulk CuO crystals were detected by high-energy diffraction above a 30% Cu content. However, the extreme copper dispersion is preserved even for higher copper contents, showing no limit of surface saturation. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Chemistry of Materials
volume
14
issue
9
pages
3686 - 3699
publisher
The American Chemical Society
external identifiers
  • wos:000178128900012
  • scopus:0036734703
ISSN
0897-4756
DOI
10.1021/cm021101u
language
English
LU publication?
yes
id
b07f7329-6ba5-4057-bfcd-5b6f0f73afa3 (old id 328422)
date added to LUP
2007-11-07 18:38:48
date last changed
2017-10-22 03:44:40
@article{b07f7329-6ba5-4057-bfcd-5b6f0f73afa3,
  abstract     = {Inert gas condensation (IGC) has been employed to produce nanoparticles of the low-temperature combustion catalyst CuOx/CeO2. For the first time we have used a multiple heating crucible setup to tailor various morphologies over the whole compositional range (2-98% Cu). The factors that control the growth, structure, and morphology of the nanocomposite have been studied. A powerful combination of complementary characterization methods has been used to elucidate the catalytic synergistics of this material. Investigations by high-resolution transmission electron microscopy (HRTEM) and energy-filtered TEM (EFTEM) are supported by X-ray photoelectron spectroscopy (XPS) and high-energy diffraction (HED) measurements. The nonstoichiometric CuOx/CeO2 composite displays an amorphous character consisting of aggregated CeO2 (ceria) nanocrystallites over which amorphous copper clusters (or a thin film of a solid solution) are finely dispersed. In the range 6similar to20% Cu, copper is predominantly located at the surface, which can give the material optimum catalytic properties. Development of crust structures, for example, core-shells, are formed in the 30similar to70% Cu concentration range and is attributable to a sequential oxidation of Ce followed by Cu and an ideal proportion of lattice expansion for the oxides. We suggest a model that illustrates the formation of the crust structure and may explain the observed extreme dispersion of copper on ceria. The helium gas pressure during the thermalization controls the crystal size and the degree of crystallite aggregation. Rounded particle shapes consisting of epitaxially interfaced nanocrystallites exhibit an X-ray amorphous character, while block-shaped crystals displaying sharp edges and distinct flat surfaces give rise to a higher X-ray crystallinity. Bulk CuO crystals were detected by high-energy diffraction above a 30% Cu content. However, the extreme copper dispersion is preserved even for higher copper contents, showing no limit of surface saturation.},
  author       = {Skårman, Björn and Nakayama, T and Grandjean, D and Benfield, RE and Olsson, E and Niihara, K and Wallenberg, Reine},
  issn         = {0897-4756},
  language     = {eng},
  number       = {9},
  pages        = {3686--3699},
  publisher    = {The American Chemical Society},
  series       = {Chemistry of Materials},
  title        = {Morphology and structure of CuOx/CeO2 nanocomposite catalysts produced by inert gas condensation: An HREM, EFTEM, XPS, and high-energy diffraction study},
  url          = {http://dx.doi.org/10.1021/cm021101u},
  volume       = {14},
  year         = {2002},
}