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- Journal Article
CO2 normally does not adsorb on atomically flat surfaces with high work functions (e.g. Cu(111)) even at lower temperatures. However, CO2 adsorption can be achieved by activating such surfaces either by introducing steps or by alkali preadsorption. In the present paper we report about thermal desorption spectroscopic (TDS), work function change (ΔΦ) and photoelectron spectroscopic (UPS, XPS) investigations of CO2 + K on the Cu(111) surface in the temperature range from 78 to 900 K. Our results demonstrate that the behaviour of the system can roughly be divided into two ranges depending on the amount of preadsorbed K: (1) at small to medium precoverages (0 < ΘK < 0.2, “ionic” K) mainly adsorbed molecular CO2 is present, associated with a “three peak” UP spectrum and a desorption in TDS around 105 K. (2) At higher coverages (0.2 < ΘK < 0.38; “metal-like” K) two high temperature desorption states between 650 and 750 K are found in TDS. The UP spectrum at 78 K is more complex and arises from a mixture of molecularly bound CO2 and a surface carbonate. The existence of two different carbon oxide species is manifested also in the O 1s spectra from XPS. For ΘK < 0.2 ΔΦ increases with CO2 adsorption. For higher coverages a decrease up to a minimum followed by an increase up to a saturation value is observed. There the coadsorptional behaviour of K and CO2 is believed to result from a direct CO2 - K interaction forming a surface carbonate species Show more
Journal / seriesSurface Science
SubjectAlkali metals; Carbon dioxide; Chemisorption; Low index single crystal surfaces; Photoelectron spectroscopy; Thermal desorption spectroscopy; Work function measurements
Organisational unit08576 - Digitaler Datenerhalt
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