A SEMIEMPIRICAL QUANTUM APPROACH TO THE FORMATION OF CARBON-DIOXIDE ADSORBATES ON PT(100) AND PT(111) CLUSTER SURFACES

The geometries and binding energies of CO2 adsorbates on Pt(100) and P t(111) cluster surfaces were calculated by means of an improved versio n of the extended Huckel molecular orbital method. The polarization of the surface by an applied electric potential and coadsorption of H at oms were included in the model. For simulated applied potentials in th e range -1.0 to 1.0 V, CO2 coordination geometries (side-on, formate) involving two adsorbate atoms bonded to the surface are favored, regar dless the surface topology and the presence of coadsorbed H atoms. In agreement with experiment, larger binding energies are always calculat ed for the Pt(100) cluster surface.