INTERACTION OF CARBON-DIOXIDE WITH POTASSIUM-PROMOTED FE(110) .2. TEMPERATURE-DEPENDENT REACTIONS

The temperature-dependent reactions of carbon dioxide and potassium coadsorbed on Fe(110) have been studied between 85 and 700 K by means of UV photoelectron spectroscopy (WS) and X-ray photoelectron spectroscopy (XPS). Since five different species are formed at 85 K (O-ox, CO, CO3n-, CO2 and a further species, probably of the composition C2O4m-), the thermal behaviour of the system is rather complex. However, quantification of the O 1s spectra by applying Gaussian fits allows a rather detailed description of the reaction paths. There are two ranges of potassium coverage, which exhibit big differences concerning the thermal stability of the carbonate species: small and medium coverages (up to 60% of a monolayer) and high coverages (exceeding 80% of a monolayer). They are separated by a narrow transition range.