Adsorption of carbonate species on silver. I. Nature of the surface bond.

E. M. PATRITO; P. PAREDES OLIVERA

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 1998 vol. 22 p. 1237 - 1245

0013-4686

The adsorption of carbon trioxide, carbonate and bicarbonate is investigated on the 111, 110 and 100 surfaces ofsilver from a quantum mechanical point of view. Several aspects of the metal/ion bonding such as the adsorbatebinding energy, charge transfer to/from the metal and the relaxation of the adsorbates upon adsorption areinvestigated. On the hollow site of Ag(110) bicoordinated carbonate has a binding energy of 226.9 kcal/mol. Thehighest binding energies for carbonate are obtained on Ag(110) while on Ag(111) and Ag(100) comparable bindingenergies are observed. The bicarbonate ion has a binding energy of 74.0 kcal/mol bicoordinated on the hollow siteof Ag(100). The binding energy of bicoordinated CO3 is 117 kcal/mol on Ag(100). There is a charge transfer towards the metal of 0.5 electrons in the case of carbonate and 0.25 electrons for bicarbonate. On the other hand, CO3 adsorption leads to a charge transfer of 1.5 electrons from the metal to the adsorbate. Adsorbed carbonate and carbon trioxide have the same formal charge of ÿ1.5 electrons and the same geometry, which is very close to that ofcarbonate compounds. For all adsorbates, the geometry distortion upon adsorption follows the same trend: the carbon-coordinated oxygen bond length increases while the bond length between the carbon atom and the noncoordinatedoxygen atom decreases. The changes in bond lengths induced by the adsorption process are between 4 to 8%. # 1998 Elsevier Science Ltd. All rights reserved.