Surface oxygen and chemical specificity at copper and caesium surfaces

The chemical specificity of surface oxygen at copper and caesium surfaces is shown to determine the reaction pathways for oxidation of methanol, carbon dioxide and ethene. Both photoelectron spectroscopy and temperature-programmed desorption establish that two reaction pathways are possible in methanol oxidation to give either formaldehyde or formate. Both preadsorbed oxygen, at low coverages, and coadsorbed oxygen activate CO2 adsorption on copper to give a surface carbonate at 300 K, whereas ethene carbon-carbon bond cleavage and carbonate formation occur at caesium surfaces at 80 K. The relevance of the data to studies by scanning tunnelling microscopy is discussed.