The interaction of HNCO with oxygen dosed Rh(111) surface has been investigated by Auger electron, electron energy loss and thermal desorption spectroscopy. The presence of adsorbed oxygen exerted no apparent influence on the weakly adsorbed HNCO (Tp = 130 K). It promoted, however, the dissociative adsorption of HNCO by forming a strong O-H bond which prevented the associative desorption of HNCO. As a result no H2 and NH3 formation occurred, in contrast with the clean surface, and the surface concentration of irreversibly bonded NCO was also increased. New products of the surface reaction were H2O and CO2, in addition to CO and N2 observed on a clean surface. From the behavior of the losses characteristic for the adsorbed NCO it appeared that the preadsorbed oxygen exerted a significant stabilizing effect on the NCO bonded to the Rh.
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