Theoretical insights into the support effect on the NO activation over platinum-group metal catalysts.

We systematically explored NO activation at metal/oxide interfaces by the combination of Sr 3 Ti 2 O 7 , Sr 3 Fe 2 O 7 , CeO 2 , anatase-TiO 2 , ZrO 2 , and γ-Al 2 O 3 supports and the platinum-group metal cluster (Pd 4 , Pt 4 , and Rh 4 ) using slab-model density functional theory calculations. These metal clusters can be strongly adsorbed at these metal oxide surfaces. The Pt 4 and Rh 4 clusters show larger adsorption energies than the Pd 4 cluster, yet the γ-Al 2 O 3 (100) surface shows smaller adsorption energies than other metal oxide surfaces. One oxygen vacancy close to the metal cluster was constructed to evaluate the NO activation at those metal/oxide interfaces. The O atom of NO refills the oxygen vacancy after NO dissociation, while the N adatom is left on the metal cluster. The exothermic process was identified for the NO activation except for the Sr 3 Fe 2 O 7 case, indicating the significant role of the interplay between the metal cluster and oxygen vacancy.