Shape stability and electronic structure of Pt3M (M = Co or Ni) alloy nanoparticles

Abstract

We studied the shape stability of Pt3M alloy nanoparticles (NPs) using density functional theory calculations, where M is Co or Ni. The relationship between the shape and durability of Pt3M NPs is reported. We evaluated the cohesive energies of face-centered cubic (fcc) and face-centered tetragonal (fct) NPs. Truncated octahedron, icosahedron, and truncated cube were considered as shapes for the fcc NPs. The cohesive energies in the truncated octahedral fcc Pt NPs were lower than other shapes, while the icosahedral fcc and truncated octahedral fct Pt3M NPs with the Pt-skin configuration were stable. Co and Ni had lower twin boundary energies than Pt, thus affecting the stability of the icosahedral fcc Pt3M NP; another factor influencing the stability was the high coordination number. An increase in Pt–M bond fraction lowered the cohesive energy of truncated octahedral fct Pt3M NPs. The expansion of the icosahedral fcc NPs competed with the shrinking effect of alloying, thus affecting the d-band center in icosahedral fcc Pt3M NPs. Due to the suppression of the charge transfer and shrinkage effect by alloying, d-band center in the facet with coordination number = 9 was adjusted to the suitable range based on the volcano plot.