INTERACTION OF HYDROGEN WITH CU3PT(111) - DISSOCIATION VIA ISOLATED PLATINUM ATOMS

The interaction of H-2 with the ordered Cu3Pt(111) surface has been studied with Auger electron spectroscopy (AES), low energy electron diffraction (LEED), thermal desorption spectroscopy (TDS), UV-photoelectron spectroscopy (UPS), and work function measurements (DELTAphi). The ordered Cu3Pt(111) surface consists of a 2 x 2 lattice of isolated Pt atoms completely surrounded by Cu atoms (d(Pt-Pt) = 5.2 angstrom). In contrast to Cu(111) hydrogen adsorption does take place. TD spectra exhibit only one H-2 desorption state of second order desorption kinetics and show no evidence for a compression of the H layer at higher coverages in contrast to Pt(111). The H induced changes in the substrate valence band spectra (UPS) suggest H adsorption at Pt sites. Preadsorption of CO on the Pt atoms blocks the H-2 adsorption, and the H coverage depends on the number of CO free Pt atoms. All these results are interpreted in terms of the Pt atoms - although isolated - to provide the channel for H adsorption.