ACTIVATION OF CARBON-MONOXIDE AND CARBON-DIOXIDE AT CESIUM-PROMOTED CU(110) AND CU(110)-O SURFACES

Through a combination of X-ray photoelectron and vibrational spectrosc opies the interaction of carbon monoxide and carbon dioxide with cesia ted Cu(110) and Cu(110)-O surfaces has been investigated. At 80 K carb on monoxide is adsorbed at an atomically clean Cu(110) surface with a characteristic loss feature at 2085 cm(-1) and O(1s) and C(1s) core-le vel binding energies at 533.8 and 290 eV, respectively. Exposure of th e CO adlayer to cesium at 80 K effects a decrease in the frequency of the loss feature to 1730 cm(-1) and on warming to 298 K this is replac ed by two loss features at 1450 and 196 cm(-1). The O(1s) peak has sim ultaneously shifted to 532 eV. The interaction of CO2 with Cu(110)-Cs at 80 K is characterized by loss features assigned to the ionic CO2 de grees-(a) and physically adsorbed CO2 species; on warming to 298 K the spectrum simplifies to generate two strong losses at 1380 cm(-1) and 1500 cm(-1) and weaker losses at 1050, 600, and 350 cm(-1) and assigne d to carbonate formation. Both chemisorbed and coadsorbed oxygen at a Cu(110)-Cs surface are highly reactive to CO with both core-level and vibrational spectroscopy providing evidence for low-energy pathways to surface carbonate via CO2delta- as an intermediate. These pathways ar e also available at atomically clean Cu(110) surfaces; i.e., in the ab sence of cesium. In this case when CO2-rich CO2-dioxygen mixtures are coadsorbed-reactive oxygen transients participate in the chemistry.