The state of metals in the Pt/Al₂O₃ and (Pt-Cu)/Al₂O₃ catalysts as indicated by IR spectroscopy with isotope dilution of ¹²C¹⁶O with ¹³C¹⁸O molecules

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• 作者：V. Yu. Borovkov ; S. P. Kolesnikov ; V. I. Koval鈥檆huk and J. L. d鈥橧tri
• 关键词：adsorption ; IR spectroscopy ; catalysts
• 刊名：Russian Chemical Bulletin
• 出版时间：May, 2007
• 出版年：2007
• 期刊代码：114_1066-5285
• 类别：ch
• 卷：56
• 期：5
• 页码：863-869
• 数据来源：sp

摘要

Adsorption of 13C18O+12C16O mixtures on the Pt(2.9%)/γ-Al₂O₃, (Pt(2.6%)+Cu(2.7%))/γ-Al₂O₃, and (Pt(2.6%)+Cu(5.1%))/γ-Al₂O₃ catalysts was studied by FTIR spectroscopy. On the metallic Pt surface at coverages close to saturation, CO is adsorbed both strongly and weakly to form linear species for which the vibrational frequencies of the isolated 13C18O molecules adsorbed on Pt are ∼1940 and ∼1970 cm−1, respectively. The redistribution of intensities of the high-and low-frequency absorption bands in the spectra of adsorbed 13C18O indicates that these linear forms are present on the adjacent metal sites. The weak adsorption is responsible for the fast isotope exchange between the gaseous CO and CO molecules adsorbed on metal. The Pt-Cu alloys, in which the electronic state of the surface Pt atoms characteristic of monometallic Pt remains unchanged, are formed on the surface of the reduced Pt-Cu bimetallic catalysts. The decrease in the vibrational frequencies of the isolated C=O bonds in the isolated Pt-CO complexes suggests that the CO molecules adsorbed on the Cu atoms affect the electronic properties of Pt.