The effects of Zr doping on the atomic and electronic properties of the ceria (111) surface were studied using first-principles density functional theory with the inclusion of on-site Coulomb interaction. The atomic structures, electronic structure, and the vacancy formation energies of the Zr-doped and undoped ceria(111) surfaces were compared. It was found that (i) Zr doping induces a severe distortion of the unreduced surface structure; (ii) at the reduced Zr-doped ceria(111) surface, the O anions around the O vacancy show much larger displacements than those on the pure CeO2(111) surface; (iii) an O vacancy was more easily formed around the Zr dopant, and the reduction energy was lowered by about 0.5eV; (iv) the excess electrons left by the removed O atom localize on the two Ce cations neighboring the vacancy and thus brings about the reduction of the two Ce4+ ions; and (v) the atomic structure modification induced by the Zr doping plays a vital role in facilitating the reduction of the ceria–zirconia solid solution as compared to the pure ceria.

Facilitated Vacancy Formation at Zr-Doped Ceria(111) Surfaces. Z.Yang, Y.Wei, Z.Fu, Z.Lu, K.Hermansson: Surface Science, 2008, 602[6], 1199-206