Interaction of CO2 with Cs-promoted Fe(110) as compared to Fe(110)/K+CO2

The interaction of CO2 with Cs-promoted Fe(110) at 85 K as well as temperature-dependent reactions between 100 and 700 K have been studied by means of ultraviolet photoelectron spectroscopy ( UPS) and X-ray photoelectron spectroscopy (XPS). Several surface species could be detected 85 K, i.e. carbon monoxide (CO); carbonate (CO3a-), physisorbed linear carbon dioxide (CO2lin) and very small amounts of oxidic oxygen (O-ox). An oxalate species (C2O4m-) could not be identified definitively, but from comparison with the literature there is evidence that C2O4m- is present. Increasing the temperature after saturation with CO2 leads to a complicated reaction behaviour. CO2 either desorbs or dissociates into CO and CO3n- or forms C2O4m- at temperatures between 85 and 160 K. Above 160 K C2O4m-, decomposes in parallel reactions into CO2, CO3n- and CO. Above 320 K. adsorbed CO either desorbs into the pas phase ol dissociates into C and O. In the temperature region between 500 and 700 K a recombination of C and O to CO and the desorption of Cs take place. As in the case of Fe(110)/K+CO2, at high alkali coverages two carbonate species could be detected which dissociate upon heating at different temperatures. The system Fel(110)/Cs+CO2 is proved to be very similar to the system Fr(110)/K+CO2. (C) 1998 Elsevier Science B.V.