Surface composition and possible rearrangement of disperse Pt and Rh catalysts: Does the presence of carbon and oxygen contribute to different catalytic properties?

U. Wild, D. Teschner, R. Schlögl, Z. Paál

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Abstract

The surface composition of Rh and Pt blacks (as determined by XPS) shows carbon and oxygen impurities in the untreated state. Oxygen on Pt is present as adsorbed O as well as OH/H2O groups and oxidized carbon. Rh was partly oxidized to Rr2C3, in agreement with UPS showing hardly any Fermi-edge intensity in untreated Rh as opposed to untreated Pt. High Fermi-edge intensities indicated a predominant metallic surface after an in situ treatment with H2 at 483 K, increasing the purity (XPS) to ∼90%. This treatment reduced Rh to metal and removed its C impurity. Pt, in turn, retained much carbon after H2 treatment, present mainly as graphitic carbon. A minor amount of CO was also detected, some of the O 1s peak belonging to it. The two metals were tested in methylcyclopentane reactions. Considering the necessity of carbon for nondegradative reactions and oxygen enhancing fragmentation, a correlation is suggested between the typical impurities of Pt and Rh and their respective catalytic propensities: the high fragmentation activity of Rh and the predominant nondegradative reactions to C6 "ring opening products" on Pt.

Original languageEnglish
Pages (from-to)93-98
Number of pages6
JournalCatalysis Letters
Volume67
Issue number2-4
Publication statusPublished - Jul 1 2000

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Keywords

  • Methylcyclopentane
  • Platinum black
  • Rhodium black
  • Surface carbon
  • Surface oxygen

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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