Infrared spectroscopic measurements were performed for NO and CO adsorbed on reduced and oxidized Ir supported on γ-Al2O3. Adsorption of NO on a reduced sample produced bands at 1900 and 1850 cm-1. These bands are attributed to NO adsorbed as NO+δ on metal atoms of larger iridium crystallites (Site A) and on iridium atoms influenced strongly by the support (Site B), respectively. Spectra of NO adsorbed on an oxidized sample showed only a single band at 1950 cm-1. This band is assigned as NO+δ on partially oxidized Ir sites. CO adsorption on a reduced sample produced bands at 2070-2060 and 2020 cm-1, which are associated with CO linearly bonded to Site A and Site B, respectively. Oxidation of the sample and subsequent adsorption of CO caused a band only at 2060 cm-1, which is assigned as CO linearly bonded to Site A. Detailed investigations were made on the effect of the pressure, adsorption temperature, and evacuation at different temperatures on the intensities of the above bands.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry