Investigation of the CO induced lifting of the (1 x 2) reconstruction on Pt{110} using synchrotron far-infrared RAIRS

We present a study of the coverage and temperature dependence of the Pt-CO stretching vibration of CO adsorbed on both the reconstructed Pt{1 1 0}-(1 x 2) and the unreconstructed Pt{1 1 0}-(1 x 1) surfaces. The metal-carbon stretching vibration is shown to be a sensitive probe of the structure of the underlying Pt{1 1 0} surface. As a function of coverage, the position of the adsorption peak shifts from 471 to 480 cm(-1) at 310 K, accompanying the adsorbate induced lifting of the reconstruction. At 115 K, where the reconstruction is not lifted, the absorption band remains centered at 466 cm(-1), however the FWHM increases from 6 cm(-1) at 0.05 L to 15 cm(-1) at saturation. The band at 466 cm(-1) is attributed to initial adsorption into atop sites on the atomic ridges followed by adsorption into atop sites on the (1 1 1) microfacets. The sensitivity of the synchrotron far-infrared RAIRS technique has allowed the lifting of the reconstruction to be followed as a function of temperature and, for the first time, allowed detection of localised lifting of the (1 x 2) reconstruction at a temperature 50 K lower than previously reported. (C) 2002 Elsevier Science B.V. All rights reserved.