Lateral interaction of H and CO coadsorbed on Cu 3Pt(111)

Abstract

The coadsorption of hydrogen and CO on the ordered Cu 3Pt(111) surface has been studied using low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), UV-photoelectron spectroscopy (UPS), and high resolution electron energy loss spectroscopy (HREELS). The main feature of the ordered Cu 3Pt(111) surface is a 2 × 2 structure of the Pt atoms in the surface, hence, Pt atoms are completely surrounded by Cu atoms. At temperatures above 180 K CO adsorbs on top of the Pt atoms. A constant hydrogen desorption temperature regardless of the CO pre-coverage in TDS indicates a repulsive CO-H interaction. In this case the HREEL spectra of the CO are not different from the spectra of CO on the clean surface. Dosing CO on a hydrogen saturated surface at 130 K leads to a shift of the hydrogen TD spectra to lower temperatures. Eventually this shift will stop accompanied by the occurrence of a new higher coordination CO adsorption state (HREELS) that has not been found on the clean surface. The experiments suggest a short-range repulsive interaction between hydrogen and CO on the ordered Cu 3Pt(111) surface.