Effects of Zr doping on stoichiometric and reduced ceria: A first-principles study.

The Zr doping in CeO₂ may change the reduction properties and therefore the redox properties of CeO₂. Using first-principles density functional theory with the inclusion of on-site Coulomb interaction for a 96-atom supercell, these effects are studied by comparing the differences in atomic structures, electronic structures, and reduction energies of the doped CeO₂ and those of the nondoped CeO₂. It is found that (1) Zr doping of the ceria structure results in important modifications involving nonequivalent O atoms; (2) the oxygen anions (still four-coordinated) next to the doping center show considerably lower reduction energies (by 0.6 eV) and larger displacements (“higher mobilities”); (3) an O vacancy is most easily created close to the Zr centers, therefore the Zr-doping centers might serve as nucleation centers for vacancy clustering; and (4) the electrons left by the released oxygen localize on two Ce cations neighboring the vacancy, which results in the reduction of two Ce⁴⁺ ions. [ABSTRACT FROM AUTHOR]