An infrared study of CO adsorption on Pt(111)

Infrared spectroscopy of isotopic mixtures is used to examine island formation during carbon monoxide (CO) adsorption on Pt(111) at 300 K. It was found that the linear CO band shifts from 2084.0 cm−1 at low coverage to 2094.7 cm−1 at saturation. This shift can be decomposed into a 14.4 cm−1 downward shift due to changes in the binding of the CO with coverage, and a 25.1 cm−1 upward shift due to dipole interactions within the adlayer. Analysis of the measured band shifts with coverage and isotopic dilution shows that no islands are formed upon CO adsorption on Pt(111) at low coverage. The interpretation of the data is less clear at high coverage. However, all of the observations can be explained without invoking island formation.