To investigate the healing of oxygen vacancies in ceria, a study was made of the

interaction of atomic and molecular oxygen and NO2 with oxygen vacancies on

gold-doped (110) and (100) surfaces using density functional theory, corrected for

on-site Coulomb interactions (DFT+U). For atomic and molecular oxygen,

adsorption at the reduced surface was favorable and resulted in an oxygen atom

sitting in an oxygen lattice site; healing the oxygen vacancy. On undoped surfaces,

O2 adsorbed as a peroxo O2

2- species. However, on the doped (110) surface a

super-oxo, O2

- species was present. When NO2 adsorbed (exothermically) at a

divacancy surface, one oxygen of the molecule sat in the vacancy site and the N-O

distances were elongated and an NO2

- anion forms, similar to the undoped surface.

Vacancy healing of ceria surfaces was favorable, even if vacancy formation was

enhanced, justifying the current focus on improving the oxidative power of ceria. A

catalytic cycle was briefly examined: the reaction of CO with adsorbed O2 on the

undoped and doped surfaces. It was found that the doped (110) surface facilitated

CO oxidation.

Healing of Oxygen Vacancies on Reduced Surfaces of Gold-Doped Ceria.

M.Nolan: Journal of Chemical Physics, 2009, 130[14], 144702