Oxygen Defects at Reducible Oxide Surfaces: The Example of Ceria and Vanadia

Abstract

Cerium and vanadium oxide-based systems play a major role in a variety of technological applications, with the reducibility of the systems being crucial to their functionality in the applications. The in-depth understanding and control of the type, density, and distribution of oxygen vacancies provide a means to influence the electronic structure and to tailor the systems’ functionality. Hence, a great deal of experimental and theoretical work has been devoted to the study of partially reduced ceria and vanadia, both surfaces and bulk. Here, theoretical data for structural and electronic properties and energetic quantities related to the formation and interaction of neutral oxygen vacancies at the CeO2(111) and V2O5(001) surfaces are reviewed, discussed and compared. Experimental findings on oxygen defects in ceria and vanadia are briefly reported. Special attention is given to the fate of the electrons left in the system upon vacancy formation, the vacancy-induced lattice relaxation, whether vacancies agglomerate or repel each other, and the ability of state-of-the-art quantum-mechanical methods to provide an accurate decription of the geometric and electronic structures of the partially reduced oxide systems as well as reliable oxygen defect formation energies.