Characterization of Au-Rh/TiO 2 bimetallic nanocatalysts by CO and CH 3CN adsorption: XPS, TEM and FTIR measurements

J. Kiss, Róbert Németh, Ákos Koós, J. Raskó

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

On X-ray photoelectron spectra of the Au-Rh/TiO 2 catalysts the position of Au4f peak was practically unaffected by the presence of rhodium, the peak position of Rh3d, however, shifted to lower binding energy with the increase of gold content of the catalysts. Rh enrichment in the outer layers of the bimetallic crystallites was experienced. The bands due to Au 0-CO, Rh 0-CO and (Rh 0) 2-CO were observed on the IR spectra of bimetallic samples, no signs for Rh +-(CO) 2 were detected on these catalysts. The band due to CH 3CN on Lewis acid centers shifted to lower wavenumbers with the increase of Rh content, which shows that the strength of Lewis acid sites weakens with the increase of Rh content of the catalysts. CH 3CN, on the other hand, dissociates producing CN (a) species even at this temperature. From the shift to higher wavenumbers of the band due to CN (a) the strengthening of the C-N bond with increasing Rh content has been established. The results were interpreted by electron donation from titania through gold to rhodium and by the higher particle size of bimetallic crystallites. The effects of catalyst composition, reaction temperature and composition of the reacting gas mixtures have been studied on the oxidation of CO in the presence of hydrogen (PROX process). The presence of both 0 2 and H 2 reduced the surface concentration of CO adsorbed on metallic sites. Mass spectroscopic analysis of the gas phase showed that gaseous C0 2 formed in the highest amount in CO + O 2 mixture, the presence of H 2 suppressed the amount of C0 2 produced. This negative effect of hydrogen was the lowest on 1% Rh/TiO 2, the highest inhibition was observed on Au/TiO 2 systems.

Original languageEnglish
Pages (from-to)3828-3836
Number of pages9
JournalJournal of Nanoscience and Nanotechnology
Volume9
Issue number6
DOIs
Publication statusPublished - Jun 2009

Fingerprint

Fourier Transform Infrared Spectroscopy
Carbon Monoxide
Adsorption
X ray photoelectron spectroscopy
methylidyne
Transmission electron microscopy
catalysts
transmission electron microscopy
Catalysts
adsorption
Rhodium
rhodium
Crystallites
crystallites
Lewis Acids
Gold
gold
Hydrogen
acids
Spectroscopic analysis

Keywords

  • Au-Rh bimetallic nanocatalysts
  • CO adsorption
  • FTIR
  • TEM
  • XPS

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Chemistry(all)
  • Materials Science(all)
  • Bioengineering
  • Biomedical Engineering

Cite this

Characterization of Au-Rh/TiO 2 bimetallic nanocatalysts by CO and CH 3CN adsorption : XPS, TEM and FTIR measurements. / Kiss, J.; Németh, Róbert; Koós, Ákos; Raskó, J.

In: Journal of Nanoscience and Nanotechnology, Vol. 9, No. 6, 06.2009, p. 3828-3836.

Research output: Contribution to journalArticle

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abstract = "On X-ray photoelectron spectra of the Au-Rh/TiO 2 catalysts the position of Au4f peak was practically unaffected by the presence of rhodium, the peak position of Rh3d, however, shifted to lower binding energy with the increase of gold content of the catalysts. Rh enrichment in the outer layers of the bimetallic crystallites was experienced. The bands due to Au 0-CO, Rh 0-CO and (Rh 0) 2-CO were observed on the IR spectra of bimetallic samples, no signs for Rh +-(CO) 2 were detected on these catalysts. The band due to CH 3CN on Lewis acid centers shifted to lower wavenumbers with the increase of Rh content, which shows that the strength of Lewis acid sites weakens with the increase of Rh content of the catalysts. CH 3CN, on the other hand, dissociates producing CN (a) species even at this temperature. From the shift to higher wavenumbers of the band due to CN (a) the strengthening of the C-N bond with increasing Rh content has been established. The results were interpreted by electron donation from titania through gold to rhodium and by the higher particle size of bimetallic crystallites. The effects of catalyst composition, reaction temperature and composition of the reacting gas mixtures have been studied on the oxidation of CO in the presence of hydrogen (PROX process). The presence of both 0 2 and H 2 reduced the surface concentration of CO adsorbed on metallic sites. Mass spectroscopic analysis of the gas phase showed that gaseous C0 2 formed in the highest amount in CO + O 2 mixture, the presence of H 2 suppressed the amount of C0 2 produced. This negative effect of hydrogen was the lowest on 1{\%} Rh/TiO 2, the highest inhibition was observed on Au/TiO 2 systems.",
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