TEMPERATURE EFFECTS ON THE INFRARED-SPECTRUM OF CARBON-MONOXIDE ADSORBED BY SUPPORTED PLATINUM

When alumina-supported platinum with adsorbed carbon monoxide is heated to 200°C an infrared band at about 2000 cm- grows in and the main band at 2060 cm-1 decreases in intensity. When the sample is allowed to cool, the 2000 cm-1 band virtually disappears and the 2060 cm-1 band increases in intensity. The main band for CO adsorbed by silica-supported platinum at 2070 cm-1 decreases in intensity on heating and increases on cooling. The 2000 cm-1 band is absent on silica-supported platinum. We tentatively attribute this band to the CO stretching vibration of linearly adsorbed CO which interacts with electron withdrawing sites on the support. The increase in the 2060 cm-1 (2070 cm-1 for Pt/SiO2) band on cooling may be due to increasing dipolar interactions enhancing the intensity of high-frequency absorbers at the expense of low-frequency absorbers. © 1990.