CO-adsorbed FTIR spectra were registered on a Nicolett 6700 spectrometer equipped with MCT detector and a diffuse reflection chamber. Prior to exposure to CO, the samples were reduced at an appropriate temperature in 5% H2 in Ar for 1 h, then cooled to room temperature in an Ar flow to remove the adsorbed hydrogen and the background spectra were collected. CO adsorption was carried out for 30 min at 5 bar pressure of CO (5 vol%) in Ar. Each spectrum was recorded with a resolution of 4 cm -1 performing 64 scans.