The role of surface Pt on the coadsorption of hydrogen and CO on Pt monolayer film modified Ru(0001) surfaces

Abstract We have investigated the impact and role of the Pt surface modification on the coadsorption of hydrogen and CO on structurally well defined bimetallic Pt monolayer island/film modified Ru(0001) surfaces with Pt contents up to a complete Pt layer, employing temperature programmed desorption (TPD) and infrared reflection absorption spectroscopy (IRRAS). Kinetic limitations in the surface diffusion are shown to play an important role for adsorption at 90 K, and lead to profound effects of the dosing sequence on the adsorption and desorption characteristics. Furthermore, they are responsible for spill-over effects during the TPD measurements, where CO ad becomes mobile and can spill-over from weakly bonding Pt monolayer areas to strongly bonding Pt-free Ru(0001) areas, which displaces D ad from these surface areas. The present findings are discussed in comparison with previous results on related metallic and bimetallic adsorption and coadsorption systems.