The interaction of CO sub 2 with potassium-promoted Cu(100): adsorption, reactions and radiation induced dissociation of CO sub 2

The coadsorption of CO sub 2 and K on Cu(110) has been studied by the methods of photoelectron spectroscopy using synchrotron radiation, high resolution electron energy loss spectroscopy (HREELS) and work function measurements ( Delta Phi ). Both weakly adsorbed molecular carbon dioxide. Chemisorbed carbonate and carbon monoxide are found at 107K. It was found that the presence of free copper sites is necessary for the adsorption of CO and the large amount of physisorbed CO sub 2 in comparison with the Cu surface completely covered with potassium. A coherent picture of the adsorption and reactions of CO sub 2 with a K modified Cu(110) surface is obtained by combination of the above mentioned spectroscopies with earlier thermally programmed desorption measurements and binding energy determinations of C 1s and O 1s. Irradiation with 125 eV photons causes a transformation of physisorbed CO sub 2 to chemisorbed CO and O. The kinetics of this photoinduced process was followed via the intensity variations of the O 1s characteristic of physisorbed and reacted CO sub 2 . The cross-section for the reaction was determined to be 3x10 exp 7 barn at a photon energy of 125 eV. Both the large cross-section and the photon energy dependence indicate that photon generated secondary electrons play a dominant role in the transformation process.