Coadsorbate effects on adsorbate vibrational properties

Surface Defects Activating New Reaction Paths: Formation of Formate during Methanol Oxidation on Ru(0001)

“…On the basis of many previous investigations, in particular work on co-adsorption of oxygen and CO, [10] we can safely assign this band to the stretching mode of CO molecules adsorbed on an on-top position on the Ru surface atoms. The spectrum reveals the existence of three main bands, around approximately 2050 cm À1 , 1800 cm À1 and 1210 cm À1 .…”

“…With increasing exposure, the first band, at 2050 cm À1 , evolves from an initial position at 2042 cm À1 to a maximum wavenumber of 2060 cm À1 and then turns back to lower wavenumbers, at the same time decreasing its intensity. On the basis of many previous investigations, in particular work on co-adsorption of oxygen and CO, [10] we can safely assign this band to the stretching mode of CO molecules adsorbed on an on-top position on the Ru surface atoms. In our co-adsorption experiment, the integrated intensity of this band is found to be about 5 times weaker than in the case of sole methanol adsorption.…”

“…The spectrum reveals the existence of three main bands, around approximately 2050 cm À1 , 1800 cm À1 and 1210 cm À1 . This chemical effect has been invoked by Jakob [10] to explain the blue-shift observed in his experiments of CO coadsorption with oxygen and hydrogen. On the basis of many previous investigations, in particular work on co-adsorption of oxygen and CO, [10] we can safely assign this band to the stretching mode of CO molecules adsorbed on an on-top position on the Ru surface atoms.…”

“…However, this extra blue-shift can be attributed to the influence of the other adsorbates, oxygen and hydrogen, the latter originating from methanol dehydrogenation. This chemical effect has been invoked by Jakob [10] to explain the blue-shift observed in his experiments of CO coadsorption with oxygen and hydrogen. Whereas the band at 2050 cm À1 can be confidently attributed to CO on top, the ascription to specific species of the other two bands is less straightforward.…”

“…We argue that during methanol co-adsorption with oxygen, blocking effects can be recognized. [11] Furthermore, in has been observed by others [10,21] that high H and O coverages on Ru(0001) coexist with adsorbed CO. The decrease in the intensity of the adsorbed species is most probably attributed to their displacement by atomic species resulting from surface reactions.…”