Explaining Cu@Pt Bimetallic Nanoparticles Activity Based on NO Adsorption.

Cu@Pt nanoparticles (NPs) are experimentally regarded as improved catalysts for the NO x storage-reduction, with higher activities and selectivities compared to pure Pt or Cu NPs, and to inverse Pt@Cu NPs. Here, a density-functional theory based study on such NP models with different sizes and shapes reveals that the observed enhanced stability of Cu@Pt compared to Pt@Cu NPs is due energetic reasons. On both types of core@shell NPs charge is transferred from Cu to Pt, strengthening the NP cohesion energy in Pt@Cu NPs, and spreading charge along the surface in Cu@Pt NPs. The negative surface Pt atoms in the latter diminish the NO bonding due to an energetic rise of the Pt bands, as detected by the appliance of the d -band model, although other factors such as atomic low coordination or the presence of an immediate subsurface Pt atom do as well. A charge density difference analysis discloses a donation/backdonation mechanism in the NO adsorption.