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Title:Charge Compensation and Ce3+ Formation in Trivalent Doping of the CeO2(110) Surface: The Key Role of Dopant Ionic Radius
Authors:Michael Nolan, 2011
Abstract: In this paper, we use density functional theory corrected for on-site Coulomb interactions (DFT+U) and hybrid DFT (HSE06 functional) to study the defects formed when the ceria (110) surface is doped with a series of trivalent dopants, namely, Al3+, Sc3+, Y3+, and In3+. Using the hybrid DFT HSE06 exchange-correlation functional as a benchmark, we show that doping the (110) surface with a single trivalent ion leads to formation of a localized MCe/ + OO• (M = the 3+ dopant), O− hole state, confirming the description found with DFT+U. We use DFT+U to investigate the energetics of dopant compensation through formation of the 2MCe′ +VO·· defect, that is, compensation of two dopants with an oxygen vacancy. In conjunction with earlier work on La-doped CeO2, we find that the stability of the compensating anion vacancy depends on the dopant ionic radius. For Al3+, which has the smallest ionic radius, and Sc3+ and In3+, with intermediate ionic radii, formation of a compensating oxygen vacancy is stable. On the other hand, the Y3+ dopant, with an ionic radius close to that of Ce4+, shows a positive anion vacancy formation energy, as does La3+, which is larger than Ce4+ ( J. Phys.: Condens. Matter 2010, 20, 135004). When considering the resulting electronic structure, in Al3+ doping, oxygen hole compensation is found. However, Sc3+, In3+, and Y3+ show the formation of a reduced Ce3+ cation and an uncompensated oxygen hole, similar to La3+. These results suggest that the ionic radius of trivalent dopants strongly influences the final defect formed when doping ceria with 3+ cations. In light of these findings, experimental investigations of these systems will be welcome.
ICHEC Project:Surface Reactions at Metal Oxides from Hybrid Density Functional Theory
Publication:The Journal of Physical Chemistry C, Vol. 115, No. 14, pp. 6671-6681 (14 April 2011). doi:10.1021/jp112112u
URL: http://dx.doi.org/10.1021/jp112112u
Status: Published

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