The adsorption of methyl radicals on oxygen-modified Mo(100) studied by HREELS

The adsorption of methyl radicals on two different oxygen-modified Mo(100) surfaces at room temperature has been studied using high-resolution electron energy-loss spectroscopy (HREELS) and low-energy electron diffraction (LEED). Previous experiments have shown that methyl radicals adsorbed to these surfaces produce CH₄, H₂ and CO as reaction products. Since the data from this earlier study was inconclusive, vibrational spectroscopic evidence was sought in order to obtain a chemical identification of the surface species. This study confirms the previous data, which suggested that methyl radicals do not form surface methoxy but rather a metal alkyl analog when adsorbed at 300 K. Methyl groups dehydrogenate at room temperature and reveal an O-H stretching vibration as well as the CH₂ scissor mode. This data is compared to the results observed when CH₃OH is adsorbed on the same surface. In the latter case, no O-H vibrations are detected in the spectrum and modes corresponding to adsorbed methoxy are seen.