The adsorption of CO2 and CO on Ca and CaO films studied with MIES, UPS and XPS

Metastable Induced Electron Spectroscopy (MIES), Ultraviolet Photoelectron Spectroscopy (UPS), and X-ray Photoelectron Spectroscopy (XPS) are employed to study the adsorption of CO2 and CO on Ca and CaO films. Ca films are prepared by evaporation of Ca onto clean Si(1 0 0) substrates. CaO films are produced by Ca evaporation in an oxygen atmosphere at a substrate temperature of 670 K. CO2 interaction with the Ca films is initiated by dissociation of the impinging molecules leading to the formation of Ca–O bonds. These Ca–O bonds are subsequently consumed in the formation of a closed CaCO3 layer on top of the surface. CO interaction with the Ca surfaces also leads to the dissociation of the molecule and the formation of Ca–O bonds. We find evidence for the subsequent formation of CO 3 2 - complexes on top of the surface. On CaO surfaces, both CO2 and CO lead to the formation of a closed CaCO3 top layer, though displaying very different reaction rates.