Adsorption dynamics and kinetics of CO2 on Fe/FeOx nanoclusters supported on HOPG



The adsorption dynamics and kinetics of CO2 on FeOx clusters have been studied using thermal desorption spectroscopy (TDS) and molecular beam scattering. According to AES data, even at good vacuum conditions, the vapor-deposited Fe clusters oxidize readily. An ensemble of metallic and oxidized Fe clusters form. Three structures at 120 K, 160 K, and 500 K are seen in CO2 TDS, which are assigned to physisorbed CO2 and carbonate decomposition. The latter structure is only present for large Fe exposures, χFe. The initial adsorption probabilities, S0, decrease with increasing impact energy. S0 increases with adsorption temperature, Ts, which is discussed in the framework of the capture-zone model (CZM). Small effects of the cluster size on the initial adsorption probabilities, S0, as well as its coverage dependence, S(Θ), have been seen. The coverage dependence of the adsorption probabilities obeys the Kisliuk precursor model, as predicted by the CZM. Copyright © 2008 John Wiley & Sons, Ltd.