Direct atomic scale analysis of the distribution of Cu valence states in Cu/γ-Al2O3 catalysts

Kai Sun, Jingyue Liu, Nigel D. Browning

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

In this paper, the microstructure of a 1 wt.% Cu/γ-Al2O3 catalyst that was reduced in a 4% hydrogen/argon atmosphere at temperatures of 523, 773 and 1073 K, is studied by Z-contrast imaging and electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Results show that the copper species are well dispersed when the catalyst is reduced below 523 K. At 773 K, separated Cu(I) and Cu(0) species are found existing as ring-like and bulk-like particles. This appears to indicate that the copper has not been reduced to its metallic form due to the interaction between the copper oxide and the support. Large spherical particles having core-shell structures with Cu(I) in the shells and Cu(0) in the cores are generated when the catalyst is reduced at 1073 K. The formation of partially oxidized copper species upon reduction at 1073 K is attributed to the metallic copper interaction with the alumina support. This study also demonstrates that high-spatial resolution Z-contrast imaging and EELS performed simultaneously can provide unique information on the morphology and chemistry of metal species in supported metal catalysts.

Original languageEnglish (US)
Pages (from-to)271-281
Number of pages11
JournalApplied Catalysis B: Environmental
Volume38
Issue number4
DOIs
StatePublished - 2002
Externally publishedYes

Keywords

  • Cu/γ-AlO
  • EELS
  • Metal-support interaction (MSI)
  • Reduction
  • STEM
  • Valence state
  • Z-contrast imaging

ASJC Scopus subject areas

  • Catalysis
  • Environmental Science(all)
  • Process Chemistry and Technology

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