Formation of mixed (NOads+COads) (1x1) islands on the Pt(100)-(hex) surface

The coadsorption of NO and CO on the reconstructed Pt(100)-(hex) surface at 300 K was studied by means of high-resolution electron energy-loss spectroscopy (HREELS). NO + CO coadsorption layers prepared in three different ways were investigated: (1) CO adsorption after coverage of the surface with NOads/(1 x 1) islands; (2) NO adsorption after coverage of the surface with CO, which was mainly adsorbed on structural defects of the reconstructed (hex) phase (low coverage of COads); and (3) NO adsorption after coverage of the surface with COads/(1 x 1) islands (high coverage of COads). In all cases the strong mutual interaction between NOads and COads molecules resulted in the formation of mixed (NOads + COads)/(1 x 1) islands. The mixed islands of NOads and COads covered unreconstructed(1 x 1) patches. The islands were separated from each other by either free (hex) phase or a region consisting of structural defects, which appeared during the course of a surface (hex)-->(1 x 1) back-reconstruction. In the mixed (NOads + COads)/(1 x 1) islands, it was found that structural defects were occupied preferentially by molecularly adsorbed CO. (C) 1998 Elsevier Science B.V. All rights reserved.