Skeletal Octahedral Nanoframe with Cartesian Coordinates via Geometrically Precise Nanoscale Phase Segregation in a Pt@Ni Core–Shell Nanocrystal

Abstract

Catalytic properties of nanoparticles can be significantly enhanced by controlling nanoscale alloying and its structure. In this work, by using a facet-controlled Pt@Ni core-shell octahedron nanoparticle, we show that the nanoscale phase segregation can have directionality and be geometrically controlled to produce a Ni octahedron that is penetrated by Pt atoms along three orthogonal Cartesian axes and is coated by Pt atoms along its edges. This peculiar anisotropic diffusion of Pt core atoms along the ⟨100⟩ vertex, and then toward the ⟨110⟩ edges, is explained via the minimum strain energy for Ni-Ni pair interactions. The selective removal of the Ni-rich phase by etching then results in structurally fortified Pt-rich skeletal PtNi alloy framework nanostructures. Electrochemical evaluation of this hollow nanoframe suggests that the oxygen reduction reaction (ORR) activity is greatly improved compared to conventional Pt catalysts.

Elemental Anisotropic Growth and Atomic-Scale Structure of Shape-Controlled Octahedral Pt–Ni–Co Alloy Nanocatalysts

“…These are the premises that led to establish {111}-Pt 3 Ni surfaces as the ideal electrocatalyst for the ORR 18,19 . Since then, many synthetic routes to obtain PtNi nanooctahedra, which ideally exhibit 8 facets with (111) atomic arrangement, have been developed, in which the co-reduction of the metal precursors takes place in the solution-phase [20][21][22][23][24] . A recent study 25 has shed light onto the growth mechanism of binary PtNi octahedral nanoparticles, revealing an anisotropic growth where a Pt-rich phase first develops into hexapod-like concave NCs in a ligand-controlled kinetic process, followed by a layer-by-layer deposition of a Ni-rich phase at the concave {111} facets.…”

The growth and degradation of binary and ternary octahedral Pt–Ni-based fuel cell catalyst nanoparticles studied using advanced transmission electron microscopy

“…Although the chemical routes for the nanoparticle synthesis are different, a comparison of the growth mechanisms described by Gan et al and Oh et al shows distinct similarities especially at the beginning of the growth [39,62]. In the two studies, growth starts very similarly from Pt-rich seeds, which develop further into concave octahedral structures.…”

“…In 2015, Oh et al investigated CO-induced phase segregation in octahedral nanoparticles [62], which were, in contrast to the work of Gan et al [39], distinctly larger and more Ni-rich. They observed geometrically highly symmetrical phase-segregated Pt-Ni nanostructures, comprising Ni octahedra encased by octahedral Pt frameworks with three intersecting perpendicular Pt axes [62].…”

“…They observed geometrically highly symmetrical phase-segregated Pt-Ni nanostructures, comprising Ni octahedra encased by octahedral Pt frameworks with three intersecting perpendicular Pt axes [62]. Small, geometrically poorly defined Pt-rich Pt-Ni alloy nanocrystals were inferred to have formed initially, with a subsequent gradual transformation into slightly concave octahedral nanoparticles ( Figure 3).…”

Emerging nanostructured electrode materials for water electrolysis and rechargeable beyond Li-ion batteries

“…Moreover, PtAu core-shell nanoparticles exhibited promising electrochemical properties, making them appealing for WE [42]. The next important group derived from alloys consists of the less expensive PtNi core-shell nanocrystals, which are of very high utility since they show a WE performance even better than supported Pt electrocatalysts [54,55]. Although the use of Pt electrocatalysts currently ensures a broad applicability of WE, the development of novel Pt-TM alloys (e.g.…”