CO adsorption and thermal stability of Pd deposited on a thin FeO(1 1 1) film

We have studied adsorption of CO on Pd deposited on a thin FeO(1 1 1) film grown on a Pt(1 1 1) substrate using temperature programmed desorption, infrared reflection absorption spectroscopy and molecular beam techniques. At sub-monolayer Pd coverage, where formation of Pd(1 1 1) single layer islands upon heating is suggested on the basis of scanning tunneling microscopy studies, the CO desorption temperature is 70–100 K lower than on a Pd(1 1 1) single crystal, which agrees well with the results of ab initio calculations. However, annealing to 600 K results in strong reduction of the CO adsorption capacity, which is rationalized in terms of significant Pd migration through the film as revealed by angular resolved photoelectron spectroscopy measurements using synchrotron radiation. The results demonstrate the complexity of Pd interaction with the thin FeO(1 1 1) film at elevated temperatures.