Does CO₂ dissociatively adsorb on Cu surfaces?

The interactions of CO₂ with a clean Cu(110) surface have been studied both in an ultrahigh-vacuum surface analytical chamber and in an attached, high-pressure cell. No adsorption or dissociation of CO₂ was measured for exposures up to 350 L at 110 K and 250 K. Exposures of 65 to 650 Torr of CO₂ at 400-600 K led to the build-up of atomically adsorbed oxygen according to the reaction CO_2.g to CO_g+O_a at a rate which increased with temperature ( approximately 16 kcal mol^-1) and decreased with reaction time, saturating in a p(2*1)-O overlayer. The observed dissociative reaction probabilities for CO₂ of approximately 10^-9-10^-11 (per collision with the surface) are favorably compared with predictions based upon the thermodynamics of adsorbed oxygen and the known kinetics of the reverse reaction: CO_g+O_a to CO_2.g. The rates are also reasonably close to the reaction probability for CO₂ reported in the reverse water-gas shift reaction over Cu-based catalysts, which suggests a catalytic redox mechanism involving the dissociative adsorption of CO₂, followed by consumption of the resulting O_a by reaction with H₂. The results also show that CO₂:CO ratios in excess of approximately 100 would be required to produce significant oxygen concentrations on copper surfaces under catalytic methanol synthesis conditions. The authors were unable to produce surface carbonate from O_a plus CO₂ on Cu(110).