Interaction of carbon dioxide with oxidised La/Cu(111)

Abstract

The interaction of carbon dioxide at 300 K with various types of pre-oxidised lanthanum films on Cu(111) has been examined in detail by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), ΔΦ(work function) measurements and temperature-programmed desorption (TPD). The exact nature and extent of the interactions of CO₂ with the LaO_x films proved to be strongly dependent on the oxide preparation and the thickness of the film, although spectral evidence points to the predominant formation of various surface carbonate complexes in all cases. On the partially-reduced surfaces there is a greater probability for irreversible adsorption, with thermal dissociation leading to the generation of gas-phase CO, but the extent of the overall adsorption process is not related to the surface oxygen vacancy concentration. The strongest binding and largest uptake of CO₂ were found on disordered, unannealed oxide films and this is discussed in the context of the properties of metal/lanthana catalysts for methanol synthesis.