Stable structure optimization of Pt-X-Cu (X = Au, Ag, Pd and Rh) trimetallic nanoparticles

Abstract Metallic nanoparticles (NPs) are becoming a hot issue in the field of catalyst because of their extraordinary catalytic potential. Especially, the Pt-alloy catalysts have drawn most of attention. Since the surface structures of Pt-alloy NPs strongly affect the catalytic performance, a thorough study of their surface structures is important for the syntheses and applications of Pt-alloy catalysts. In this study, we investigate the stable structures of tetrahexahedral (THH) Pt-X-Cu(X = Au, Ag, Pd and Rh) trimetallic NPs by adopting Q-SC many body potentials and an improved genetic algorithm. Moreover, the structural stability and segregation behavior of the four Pt-alloy NPs with different particle sizes and composition ratios are explored. The simulation results reveal that Pt atoms firstly have a trend to distribute little fractions on the surface for Pt-Au-Cu, Pt-Ag-Cu and Pt-Pd-Cu NPs, even its composition is lower than 10%, then they gradually occupy the inner layers. Meanwhile, Cu and X (Au, Ag, Pd) atoms preferentially segregate to the surface. Especially, Au and Ag atoms exhibit stronger surface segregation than Cu ones when their compositions are the same. For Pt-Rh-Cu trimetallic NPs, Rh atoms prefer to distribute in the interior, while Pt and Cu atoms tend to occupy the surface. Additionally, the Pt fractions on the surface of Pt-Rh-Cu NPs are higher than that in the other three trimetallic NPs. Finally, we have predicted a linear relation between the surface Pt fractions and Pt compositions for the four trimetallic NPs when Pt composition is bigger than the surface-to volume ratio.