Oxygen vacancy clusters on ceria: Decisive role of cerium f electrons

摘要: Defects such as oxygen vacancies dominate the electronic and chemical properties of ceria. However, fundamental understanding defects, especially clusters vacancies, is sparse. In this work, we use density-functional theory with addition Hubbard U term to investigate various including vacancy monomer, dimer, trimer, tetramer, in which subsurface can also be involved. We show that individual surface have very similar stabilities; dimer consisting two not reported experimentally, stable theory; between trimers observed experiments, triangular cluster more than double linear containing a vacancy, agrees some experiments but disagrees others; tetramer emerges most among possible tetramers although it less those no vacancies. These findings are rationalized terms change upon removal oxygen, namely, localization resulting excess electrons on Ce f orbitals. identify correlation energy levels occupied states reduced ions their coordination numbers, proves pivotal interpreting formation stability Comparisons made apparent discrepancies discussed. Results for gold adsorption presented, implications these catalysis briefly