CO chemisorption on PdCu(110): a work function study

The work function change (ΔΦ) that occurs upon CO chemisorption on PdCu(110) single crystal was studied using the Kelvin probe technique. The ΔΦ measurements were carried out for various surface compositions ranging from 100% Pd to 100% Cu, which were prepared by sputtering and annealing the sample at different conditions. Auger Electron Spectroscopy (AES) and Thermal Desorption Spectroscopy (TDS) were used to characterise the surface before and after each ΔΦ measurement. The results obtained in this study prove that the ΔΦ technique is very sensitive to changes in surface composition and can be therefore successfully used to determine quantitatively the top layer composition of PdCu(110) single crystal alloy. The ΔΦ results reported here indicate a charge transfer from Pd to Cu in PdCu alloys. As a result of this transfer process, the back donation of electrons from Pd to adsorbed CO is reduced and the dipole moment of adsorbed CO on Pd becomes smaller