Adsorption and dissociation of CO on Fe(100) at low coverage

Abstract

Abstract Adsorption and dissociation of low coverage CO on Fe(100) has been studied. The combination of high resolution electron energy loss spectroscopy (HREELS) and temperature programmed reaction spectroscopy (TPRS) has been used to monitor the CO dissociation process in detail. Adsorption of CO at low temperature (103 K) results in associative adsorption. The adsorption state is characterized by a CO stretching frequency around 1170 cm −1 . For CO coverage below 0.15 monolayer (ML), where 1 ML is defined as the number of top layer Fe atoms on the unreconstructed (100) surface, all adsorbed CO dissociates on the surface upon heating to high temperature (423 K). With CO coverage higher than 0.15 ML, direct desorption of adsorbed molecules takes place in competition with the dissociation process. Reducing the CO coverage and annealing the adsorbed CO overlayer both cause the CO stretching frequency to decrease. Dissociated CO is characterized by MO and MC vibrational peaks, located at 400 and 520 cm −1 respectively.