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Anchoring Sites for Initial Au Nucleation on CeO2{111}: O Vacancy versus Ce Vacancy Changjun Zhang,

Summary: Anchoring Sites for Initial Au Nucleation on CeO2{111}: O Vacancy versus Ce Vacancy
Changjun Zhang,
Angelos Michaelides,
David A. King,
and Stephen J. Jenkins*,
Department of Chemistry, UniVersity of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K., and
Materials Simulation Laboratory, London Centre for Nanotechnology & Department of Chemistry, UniVersity
College London, London, WC1H 0AH, U.K.
ReceiVed: NoVember 17, 2008; ReVised Manuscript ReceiVed: February 5, 2009
Gold atoms act as anchoring sites for gold nanoparticles in the ceria-catalyzed water-gas shift reaction;
however, the anchoring site of the nanoparticle is a matter of debate. Both oxygen and cerium vacancies have
been suggested as the anchoring sites in different studies. Aiming to provide insight into this issue, we utilize
density functional theory and ab initio thermodynamics approaches to investigate the formation of various
vacancies at a CeO2{111} surface, both with and without gold adatoms. We find that, under reaction conditions,
the cerium vacancy is much harder to form and is much less stable than the oxygen vacancy, regardless of
the absence or presence of gold on the surface. Gold adsorption at the oxygen vacancy site is strongly preferred
to that on the cerium vacancy; the latter becomes favorable only near the extreme oxygen-rich limit, which
would not be achievable under the reaction conditions. Other possible vacancies have also been examined.
We find that in addition to a single oxygen vacancy, oxygen vacancy clusters could also be anchoring sites
for gold nucleation. This study lays a foundation toward understanding the boundary structure between Au


Source: Alavi, Ali - Department of Chemistry, University of Cambridge


Collections: Chemistry