Investigation of the CO induced lifting of the (1×2) reconstruction on Pt{1 1 0} 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}-(1×2) and the unreconstructed Pt{1 1 0}-(1×1) 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 (1×2) reconstruction at a temperature 50 K lower than previously reported.