The adsorption of CO2 on the clean and potassium-predosed Pd(100) surface is studied using Auger electron, electron energy loss (in the electronic range), and thermal desorption spectroscopies. Adsorption of CO2 on a clean Pd(100) surface is weak and nondissociative. However, the preadsorbed potassium dramatically affected the adsorption behavior of CO2 on Pd(100) and it caused significant changes in the electron energy loss spectrum of adsorbed CO2. It increased (i) the amount of weakly adsorbed CO2, (ii) the rate of CO2 adsorption, and (iii) the binding energy of CO2, and (iv) it induced the formation of new adsorption states and lowered the activation barrier for dissociation. The lowest potassium coverage where the dissociation of CO2 was detected was θK = 0.21. The peak temperatures for CO desorption were 624 and 693 K, which are significantly higher than those measured for the clean Pd(100) surface. The adsorption of CO2 on potassiumdosed Pd leads to a work function increase of 2.20 eV at nearly monolayer of potassium. This indicates a substantial charge transfer from the potassium-dosed metal to an empty CO2πr* orbital; as a result the bonding and the structure of adsorbed CO2 are basically changed. In the interpretation of the data a direct interaction between preadsorbed K and CO2 leading to the formation of carbonate and CO is also considered.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry