The nature of oyxgen states on the surfaces of CeO2 and La-doped CeO2

The oxygen states on CeO2 surfaces were investigated with DFT + U calculations. The results reveal the variable nature of the oxygen states, including the never before modeled intrinsic peroxide surface defect. Under O-rich conditions, the peroxide defects on the (1 0 0) and (1 1 0) surfaces is more stable than oxygen vacancies. On surfaces doped with La (III) it is found that under O-rich conditions the (1 0 0) and (1 1 0) surface will preferentially form peroxide ions in response to the presence of the dopants while the (1 1 1) surface prefers oxygen vacancies. Calculated shifts in core levels match experimental binding energies, further suggesting the presence of peroxide species.