An atomistic thermodynamics study of the structural evolution of the Pt3Ni(111) surface in an oxygen environment

Abstract

The structural evolution of the Pt3Ni(111) surface under oxidizing conditions was studied by ab initio atomistic thermodynamics. The thermodynamic phase diagram from Ni-rich to Pt-rich conditions with oxygen coverages up to one monolayer was constructed from their 560 possible surface structures. With an increase in the oxygen chemical potential, there were only two types of thermodynamically stable structures, which were a clean Pt-skin surface and a Ni-skin surface with chemisorbed oxygen, regardless of the underlying Pt-rich or Ni-rich conditions. Bimetallic surfaces with chemisorbed oxygen were only metastable. The detail analysis revealed that the structural evolution is determined by the factors of segregation cost, difference between oxygen-metal (Pt and Ni) bonding strength, and oxygen chemical potential.

Surface Segregation in Bimetallic Nanoparticles: A Critical Issue in Electrocatalyst Engineering

“…DFT calculation results have demonstrated that the oxidizing atmosphere (such as O 2 or NO) could promote Ni segregating onto the surface of Pt–Ni NPs. Nevertheless, due to the weak bonding with H and C, Ni surface segregation is not remarkable in a reducing atmosphere (such as H 2 or CO) . This was also confirmed by experiments .…”

Enhanced dry reforming of methane on Ni and Ni-Pt catalysts synthesized by atomic layer deposition

“…[34] The lattice constant for the NiPt bulk alloy in a ratio A phase diagram was generated using atomistic thermodynamics, as described in detail in previous work. [35,36] Briefly, the most stable surface structure at a given set of chemical potentials is the one that minimizes the surface energy:…”

Surface segregation and oxidation of Pt3Ni(1 1 1) alloys under oxygen environment

“…As well known, the stability in electrochemistry is one of the critical factors to consider for its successful application to fuel cell. Consequently, the issues of surface segregation of TM in Pt 3 TM system and its loss of reactivity have become the most important problems to resolve [7,8]. Previously, the stability of Pt-3d TM system was investigated with DFT calculation, showing the structural evolution under various reaction conditions [7].…”

“…ultrahigh vacuum condition (UHV) and CO conditions, while 3d TM-skin surface become more stable under oxidizing condition. Furthermore, the group looked into the case of oxygen induced segregation of Pt 3 Ni(1 1 1) system and calculated the corresponding phase diagram [8]. According to their calculation, under UHV condition, the Pt-skin surface is energetically more stable.…”