Adsorption on ordered binary alloy surfaces: Hydrogen adsorption on the clean and co-covered Cu3Pt(111) surface

The adsorption of hydrogen, as well as the interaction of adsorbed CO and hydrogen, on the Cu3Pt(111) surface have been studied using thermal desorption spectroscopy (TDS), high resolution electron energy loss spectroscopy (HREELS) and work function change measurements (Delta Phi). The results show that hydrogen adsorption and dissociation occur via platinum sites. The process proceeds with second order kinetics with respect to the number of platinum sites available. The desorption spectra are successfully simulated using a lattice gas model. From the simulations the desorption and lateral interaction energies are deduced, showing a weak hydrogen-hydrogen repulsion. The interaction of coadsorbed CO and hydrogen has also been investigated. In contrast to the Pt(111) surface where a lateral segregation of the two adsorbed species takes place, the results presented here suggest a mixed overlayer.