THE ADSORPTION AND DISSOCIATION OF CARBON-MONOXIDE ON CLEAN AND OXYGEN-MODIFIED MO(110) SURFACES

The adsorption and the dissociation of CO on clean and oxygen-modified Mo(110) surfaces have been investigated using high-resolution electron energy loss spectroscopy (EELS) and thermal desorption mass spectrometry (TDS). An inclined CO species with a nu(CO) of 1345 cm-1 has been observed as the only adsorbed species on Mo(110) at low CO coverages at 120 K. It can either be converted completely to atomic carbon and oxygen through a dissociation channel, via a stable intermediate with a nu(CO) of 1130 cm-1, or be converted completely to conventionally-bonded CO (terminal and/or bridging) through a channel induced by the additional adsorption of either CO or O2, via an intermediate with a nu(CO) of approximately 1500 cm-1. Preadsorption of a saturation coverage of oxygen on Mo(110) preferentially inhibits the CO-dissociation channel. The distinct nu(CO) vibrational frequencies due to CO adsorbed in different orientations allow us to propose a detailed picture of the reaction channels leading to CO dissociation and to inhibition of CO dissociation on Mo(110).