Infrared emission and theoretical study of carbon monoxide adsorbed on alumina-supported Rh, Ir, and Pt catalysts

Tamás I. Korányi, J. Mihály, Éva Pfeifer, Csaba Németh, Tatiana Yuzhakova, J. Mink

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Abstract

The infrared emission spectra of CO adsorbed on alumina-supported 1, 3, and 5 wt % Rh, Ir, and Pt metal-containing catalysts were studied at 423 and 473 K. While CO is adsorbed in dicarbonyl (dimer), linearly (on-top) bonded and bridged carbonyl forms on rhodium and platinum, the dimer form is dominant on iridium. The relative intensity of Rh-CO and Ir-CO linear bands decrease with increasing temperature compared to the intensity of the dicarbonyl bands; the corresponding bands on Pt behave the opposite way. Two dicarbonyl and two linear Pt-CO bands were identified in the infrared spectra of Pt/Al2O 3 catalysts. The surface structure (kinked or planar Pt atoms), the dispersity of the metal, the temperature, and the quantity of adsorbed CO on the surfaces all have an effect on the fine structure of the Pt-CO stretching bands. The metal-carbon and CO stretching force constants were calculated for surface dicarbonyl, linearly bonded CO, and bridged carbonyl species. The metal-carbon stretching wavenumbers and force constants were predicted and compared between surface species and metal carbonyl complexes. The iridium-carbon bonds were found always stronger than the Rh-C and Pt-C ones in all surface species. The observed stretching wavenumbers and force constants seem to support the idea that CO and metal-carbon bonds are always stronger in metal carbonyl complexes than in adsorbed surface species. The distribution and mode of CO adsorption on surface metal sites can be effectively studied by means of infrared emission spectroscopy.

Original languageEnglish
Pages (from-to)1817-1823
Number of pages7
JournalJournal of Physical Chemistry A
Volume110
Issue number5
DOIs
Publication statusPublished - Feb 9 2006

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Aluminum Oxide
Carbon Monoxide
carbon monoxide
aluminum oxides
Infrared radiation
catalysts
Catalysts
Metals
metals
Stretching
carbon
iridium
Carbon
Iridium
infrared spectra
dimers
Dimers
rhodium
metal surfaces
emission spectra

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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Infrared emission and theoretical study of carbon monoxide adsorbed on alumina-supported Rh, Ir, and Pt catalysts. / Korányi, Tamás I.; Mihály, J.; Pfeifer, Éva; Németh, Csaba; Yuzhakova, Tatiana; Mink, J.

In: Journal of Physical Chemistry A, Vol. 110, No. 5, 09.02.2006, p. 1817-1823.

Research output: Contribution to journalArticle

Korányi, Tamás I. ; Mihály, J. ; Pfeifer, Éva ; Németh, Csaba ; Yuzhakova, Tatiana ; Mink, J. / Infrared emission and theoretical study of carbon monoxide adsorbed on alumina-supported Rh, Ir, and Pt catalysts. In: Journal of Physical Chemistry A. 2006 ; Vol. 110, No. 5. pp. 1817-1823.
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abstract = "The infrared emission spectra of CO adsorbed on alumina-supported 1, 3, and 5 wt {\%} Rh, Ir, and Pt metal-containing catalysts were studied at 423 and 473 K. While CO is adsorbed in dicarbonyl (dimer), linearly (on-top) bonded and bridged carbonyl forms on rhodium and platinum, the dimer form is dominant on iridium. The relative intensity of Rh-CO and Ir-CO linear bands decrease with increasing temperature compared to the intensity of the dicarbonyl bands; the corresponding bands on Pt behave the opposite way. Two dicarbonyl and two linear Pt-CO bands were identified in the infrared spectra of Pt/Al2O 3 catalysts. The surface structure (kinked or planar Pt atoms), the dispersity of the metal, the temperature, and the quantity of adsorbed CO on the surfaces all have an effect on the fine structure of the Pt-CO stretching bands. The metal-carbon and CO stretching force constants were calculated for surface dicarbonyl, linearly bonded CO, and bridged carbonyl species. The metal-carbon stretching wavenumbers and force constants were predicted and compared between surface species and metal carbonyl complexes. The iridium-carbon bonds were found always stronger than the Rh-C and Pt-C ones in all surface species. The observed stretching wavenumbers and force constants seem to support the idea that CO and metal-carbon bonds are always stronger in metal carbonyl complexes than in adsorbed surface species. The distribution and mode of CO adsorption on surface metal sites can be effectively studied by means of infrared emission spectroscopy.",
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N2 - The infrared emission spectra of CO adsorbed on alumina-supported 1, 3, and 5 wt % Rh, Ir, and Pt metal-containing catalysts were studied at 423 and 473 K. While CO is adsorbed in dicarbonyl (dimer), linearly (on-top) bonded and bridged carbonyl forms on rhodium and platinum, the dimer form is dominant on iridium. The relative intensity of Rh-CO and Ir-CO linear bands decrease with increasing temperature compared to the intensity of the dicarbonyl bands; the corresponding bands on Pt behave the opposite way. Two dicarbonyl and two linear Pt-CO bands were identified in the infrared spectra of Pt/Al2O 3 catalysts. The surface structure (kinked or planar Pt atoms), the dispersity of the metal, the temperature, and the quantity of adsorbed CO on the surfaces all have an effect on the fine structure of the Pt-CO stretching bands. The metal-carbon and CO stretching force constants were calculated for surface dicarbonyl, linearly bonded CO, and bridged carbonyl species. The metal-carbon stretching wavenumbers and force constants were predicted and compared between surface species and metal carbonyl complexes. The iridium-carbon bonds were found always stronger than the Rh-C and Pt-C ones in all surface species. The observed stretching wavenumbers and force constants seem to support the idea that CO and metal-carbon bonds are always stronger in metal carbonyl complexes than in adsorbed surface species. The distribution and mode of CO adsorption on surface metal sites can be effectively studied by means of infrared emission spectroscopy.

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