Adsorption and dissociation of carbon trioxide on Ag(100)

Abstract

ABSTRACT:Using density functional theory methods, we have studied carbon trioxide, its adsorption and dissociation on Ag(100). In the gas phase, two isomers are found, D 3h and C 2v , with the latter of 2.0 kcal mol −1 lower in energy at the PW91PW91/6-31G(d) level. For CO 3 on Ag(100), the calculated adsorption energy is 91.2 and 89.1 kcal mol −1 for the bi-coord perpendicular and tri-coord parallel structures, respectively. Upon the adsorption, 0.50 ∼ 0.56 electron is transferred from silver to CO 3 , indicative of significant ionic characters of the adsorbate-surface bonding. In addition, the geometry of CO 3 is largely changed by its strong interaction with silver. For CO 3(ad) → O (ad) + CO 2(gas) , the energy barrier is calculated to be 19.8 kcal mol −1 through the bi-coord path. The process is endothermic with an enthalpy change of +17.3 ∼ +26.7 kcal mol −1 and the weakly chemisorbed CO 2 is identified as an intermediate on the potential energy surface.

Formation, Binding, and Stability of O-Ag-CO2-Ag-O Compounds on Ag(100) Investigated by Low Temperature Scanning Tunneling Microscopy and Manipulation

“…One remaining depression at the border of the image suggests that this novel species consists of three oxygen atoms and one carbon atom, i.e. carbon trioxide, which might be anionic according to ref . In contrast to the O-CO 2 compound discussed above, this species is stable under manipulation as high as 7 eV.…”

“…On Ag(100) it has been suggested that CO 2 can only be stabelized on oxygen precovered surfaces , and the species produced has been attributed to carbonate . Recent DFT (density functional theory) calculations found two almost isonergetic forms of CO 3 , a bicoordinated perpendicular adsorption and a near parallel tricoordinated form . This study calculated a charge transfer of approximately 0.5 e. Furthermore the dissociation of the species into adsorbed oxygen and desorbed CO 2 was calculated.…”

“…The oxygen atom is negatively charged on Ag(100). 16 Though an attraction of O δwith the carbon atom of CO 2 could be envisioned this is at odds with the bonding of the molecule to two oxygen atoms. However, the four silver atoms adjacent to the oxygen atom have been calculated to be electron deficient because of charge transfer to the oxygen atom.…”

CO Oxidation by Molecular and Atomic Oxygen on Ag(100): A Density Functional Theory Study

“…For the reaction of CO oxidation on silver, the formation of surface carbonate species (CO 2(g) + O (ad) → CO 3(ad) ) has been identified . Two adsorption structures are bicoordinated perpendicular and tricoordinated parallel with calculated adsorption energy of 91.2 and 89.1 kcal/mol, respectively.…”

“…All calculations were performed using the suite program of Gaussian 09 . The pw91pw91 hybrid exchange–correlation functional , was used, which has shown good reliability and accuracy in previous reports. − For silver, the effective core potential (ECP) of Lanl2 combined with the DZ basis set was adopted, − while for O and C atoms, the full electron basis set of 6-31G­(d) was employed. − All stationary points on the potential energy surface (PES) were verified by calculated vibrational frequencies at the same theoretical level as used in the geometry optimization. To locate a transition state (TS), a relaxed PES scan was carried out first to find the structure with the highest energy on the reaction path.…”