Interfacial properties of NM/CeO₂(111) (NM = noble metal atoms or clusters of Pd, Pt and Rh): a first principles study

Results from first principles calculations present a rather clear atomic and electronic level picture of the interaction of single noble metals (NM: Pd, Pt and Rh) and the corresponding NM₄ clusters with a CeO₂(111) surface. The most preferable adsorption sites for both the Pd and Pt adatoms are the surface O-bridge sites, while the Rh adatom prefers to stay at the O-hollow site. The Rh adatom shows much stronger interaction with the CeO₂(111) surface than the Pd and Pt adatoms do, while the Pd adatom has the smallest adsorption energy. The dependence of the Rh/ceria interfacial properties on the value of the Hubbard U-term was tested systematically.

The small clusters show stronger interaction than the corresponding single NM adatoms on the CeO₂(111) surface. The reaction of was found for both the single NM adatoms and the small cluster adsorbate, indicating that NM adsorbates were mainly oxidized by the surface Ce ions with obvious charge transfer from NM to the CeO₂(111) surface. The three base atoms of the small clusters that bonded with the CeO₂(111) surface showed positive charges, while the top metal atoms of the NM₄ clusters had a small negative charge.