An infrared spectroscopic study of CO and NO adsorption on bimetallic Pd-Rh/SiO2 catalysts

✍ Scribed by Y.J. Mergler; D.R.G. Ramsaransing; B.E. Nieuwenhuys

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 737 KB
• Volume: 113
• Category: Article
• ISSN: 0165-0513
• DOI: 10.1002/recl.19941131005

✦ Synopsis

Abstract

Pure Pd/SiO~2~, pure Rh/SiO~2~, and bimetallic PdRh/SiO~2~ catalysts, with Pd and Rh in the atomic ratios of 75/25 at% and 50/50 at%, were studied by means of infrared (IR) spectroscopy. Spectra of adsorbed CO and NO were recorded in the temperature range from 298 to 573K. The IR spectra obtained for the bimetallic catalysts exhibit characteristic features of both Pd and Rh. The results point to the presence of alloy crystallites with properties between those of the constituent metals. Most likely the PdRh(1:1)/SiO~2~ catalyst consists of small Rh clusters or atoms, surrounded by Pd, whereas for the PdRh(3:1)/SiO~2~ catalyst the surface consists primarily of Pd. However, in the presence of NO, Rh migrates to the surface, due to the dissociation of NO and the concomitant oxidation of the metal particles. No indication of mixed sites, consisting of both Pd and Rh atoms, was found. The results are compared with those previously reported for Pt‐Rh catalysts.