Evidence for subsurface ordering of oxygen vacancies on the reduced CeO2(111) surface using density-functional and statistical calculations

G. E. MURGIDA; M. V. GANDUGLIA PIROVANO

PHYSICAL REVIEW LETTERS

AMER PHYSICAL SOC

Lugar: New York; Año: 2013 vol. 110 p. 246101 - 246101

0031-9007

AbstractOxygen vacancies on ceria surfaces play a crucial role in catalytic applications, yet whether vacancies are at surface or subsurface sites on reduced CeO2(111), and whether vacancies agglomerate or repel each other, is still under discussion, with few and inconsistent experimental results. By combining density-functional theory with the DFT+U approach and statistical thermodynamics, we show that the energetically most stable near-surface oxygen vacancy structures for a broad range of vacancy concentrations, Θ (1/16 ≤ Θ ≤ 1 monolayer), have all vacancies at subsurface oxygen sites, and predict that the thermodynamically stable phase for a wide range of reducing conditions is a (2×2) ordered subsurface vacancy structure (Θ = 1/4). Vacancy induced lattice relaxations effects are crucial for the interpretation of the repulsive interactions which are at the basis of the vacancy spacing in the (2×2) structure. The findings provide theoretical data to support the interpretation of the most recent experiments, bringing us closer to solve the debate.