A molecular orbital study of surface–adsorbate interactions during the oxidation of CO on the Pt(1 1 1) surface

A Langmuir–Hinshelwood type pathway for the oxidation of CO on the Pt(1 1 1) surface is analysed within a tight binding scheme based on the extended Hückel method. A partitioning of the total electronic energy serves to highlight both CO and O derived contributions to the reaction barrier, the extent to which the surface mediates interactions between the adsorbates and the roles of the individual CO and O orbitals in OC–O bond formation. action barrier is interpreted to be the result of a surface-mediated coactivation of CO and O on the surface. In the initial stages of OC–O bond formation a “side-on” donation of electron density from the p-orbitals on O to the empty CO(2π) orbitals on CO occurs. The transition from reactants to products is characterized by the formation of a carboxylate (CO2−) moiety on the surface. The role of the O s and p orbitals in OC–O bonding is discussed.