THE INTERACTION OF CO2 WITH POTASSIUM-PROMOTED CU(100) - ADSORPTION, REACTIONS AND RADIATION-INDUCED DISSOCIATION OF CO2

The coadsorption of CO2 and K on Cu(110) has been studied by the metho ds of photoelectron spectroscopy using synchrotron radiation, high res olution electron energy loss spectroscopy (HREELS) and work function m easurements (Delta Phi). Both weakly adsorbed molecular carbon dioxide , chemisorbed carbonate and carbon monoxide are found at 107 K. It was found that the presence of free copper sites is necessary for the ads orption of CO and the large amount of physisorbed CO2 in comparison wi th the copper surface completely covered with potassium. A coherent pi cture of the adsorption and reactions of CO2 with a potassium modified Cu(110) surface is obtained by combination of the above mentioned spe ctroscopies with earlier thermally programmed desorption measurements and binding energy determinations of C 1s and O 1s. Irradiation with 1 25 eV photons causes a transformation of physisorbed CO2 to chemisorbe d CO and O. The kinetics of this photoinduced process was followed via the intensity variations of the O 1s characteristic of physisorbed an d reacted CO2. The cross-section for the reaction was determined to 3 X 107 barn at a photon energy of 125 eV. Both the large cross-section and the photon energy dependence indicate that photon generated second ary electrons play a dominant role in the transformation process.