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 SrTiO, SrFeO, CeO, anatase-TiO, ZrO, and γ-AlO supports and the platinum-group metal cluster (Pd, Pt, and Rh) using slab-model density functional theory calculations. These metal clusters can be strongly adsorbed at these metal oxide surfaces. The Pt and Rh clusters show larger adsorption energies than the Pd cluster, yet the γ-AlO(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 SrFeO case, indicating the significant role of the interplay between the metal cluster and oxygen vacancy.