Density Functional Theory Study of the Adsorption of Au Atom on Cerium Oxide: Effect of Low-Coordinated Surface Sites

摘要

Periodic density functional calculations within the LDA+U and GGA+U formalisms have been carried for slabs representing the CeO2(111) surface and a stepped model surface. The surface active sites have been determined and the chemical bond between Au and the underlying substrate quantified by means of analysis of Bader charges and calculated magnetic moments. For most of the active sites involving O atoms at (111) terraces or at the corresponding step edges the adsorption energy is very similar (～0.7 eV), and adsorbed Au remains essentially neutral. However, the interaction of Au with one of the facets intersecting the (111) terrace is much stronger (2.4 eV), and the adsorbed metal atom is oxidized. The present results permit one to understand the very large effect of nanostructured ceria on the activity of Au supported catalysts reported recently.