ION DIPOLE INTERACTIONS BETWEEN ADSORBED CO AND SUPPORT CATIONS IN PTK-LTL/

The adsorption of carbon monoxide on a non-acidic Pt/K-LTL catalyst ha s been studied by diffuse reflectance and transmission IR spectroscopy . The CO spectrum is strongly dependent on the experimental conditions . Adsorption on the small Pt clusters in the presence of water gives l inear-CO bands between 2060 and 1990 cm-1 and a bridging-CO band aroun d 1800 cm-1. In the absence of water, the linear bands are red shifted to about 1940 and 1720 cm-1, respectively. The frequency shift is att ributed to an ion-dipole interaction between adsorbed CO and support c ations. The ion-dipole interaction is screened by the adsorbed water l eading to a smaller red shift in the CO stretching frequency.