Adsorption of CO on Co(0001) and Pt-Co(0001) surfaces:: an experimental and theoretical study

CO adsorption on Co(0001) and Pt submonolayer deposits on Co(0001) at room temperature have been investigated by combining the surface techniques of low-energy electron diffraction and X-ray and UV photoelectron spectroscopy. The influence of bimetallic system formation on the CO adsorption was studied, CO is molecularly adsorbed on both surfaces, The saturation coverage under ultrahigh vacuum conditions corresponds to a well-ordered (root3 x root3)R30 degrees structure in the presence of Pt, The CO uptake on Pt-Co(0001) was found to be lowered in comparison with Co(0001) as the platinum coverage increased between 0 to 0.6 ML, However, CO is adsorbed both on the Pt and Co areas, It is shown that CO is located in the top Pt sites, with an adsorption energy reduced by 38% with respect to the pure Pt(111) surface, This result is in good agreement with our theoretical results of CO chemisorption energy an a pseudomorphic Pt overlayer supported by Co(0001), A decreased Pt density of states at the Fermi level and a high binding energy shift of the d-band center in comparison with the pure metal was observed both experimentally and theoretically, (C) 2000 Elsevier Science B,V, All rights reserved.