Strain‐Enhanced Metallic Intermixing in Shape‐Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics

Abstract

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd‐Ni‐Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low‐temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape‐controlled multimetallic nanoparticles tailored to each potential application.

Modulating Electronic Structure of an Au‐Nanorod‐Core–PdPt‐Alloy‐Shell Catalyst for Efficient Alcohol Electro‐Oxidation

“…[1][2][3][4][5][6] Compared with hydrogen in proton-exchange membrane fuel cells, DAFCs effectively controlled, up to the difference of intrinsic lattice parameters between the core and the shell. [34][35][36][37][38][39][40][41] For example, an expanded strain increases the d-band center of the active shell, resulting in strengthened adsorption of ethanol and OH species, and eventually much facilitated ethanol electrooxidation. [33] Moreover, the exposed crystal plane on the shell is possible to be modified during an epitaxial growth process.…”

Noble Metal‐Based Multimetallic Nanoparticles for Electrocatalytic Applications

“…Reproduced with permission. [ 242 ] Copyright 2020, Wiley‐VCH. g) Schematic illustration of epitaxial Cu shell formation on 4H (or 4H/fcc) Au nanorods.…”

“…[ 241 ] Recently, Tsung and co‐workers reported an effective strategy to prepare intermetallic alloy shells on Pd cores through thermal intermixing of Pt and Ni from epitaxially grown Pt and Ni shells. [ 242 ] Compared to thicker Ni–Pt shells on Pd, the 4‐layered Pd–(Ni–Pt) 2 (Pd–(Ni–Pt–Ni–Pt)) core–shell structure (Figure 12e,f ) induced strain and provided a shorter diffusion length between Pt and Ni, so that only 400 °C was sufficient for full mixing of Pt and Ni to produce intermetallic PtNi 3 shells on Pd nanocubes, while 2‐layered Pd–(Ni–Pt) with thicker shells of Pt and Ni showed incomplete intermixing after annealing. Finally, epitaxial shell growth on unconventional phases has recently been explored by Zhang and co‐workers, starting from 4H/fcc Au nanorods, 2H Pd nanoparticles, and 4H(or 4H/fcc) Au nanorods to prepare 4H/fcc Au@Pd, [ 243 ] fcc‐2H‐fcc Pd@M (M = Au, Ag, or Pt), [ 244 ] and 4H(or 4H/fcc) Au@Cu nanoparticles (Figure 12g ) [ 245 ] under mild conditions, which are already well known for shell growth.…”

Pt‐based Intermetallic Nanocatalysts for Promoting the Oxygen Reduction Reaction

“…It is also highly expected that this method will be applicable for the preparation of shape‐controlled intermetallic nanocrystals, as the shape of the product is roughly dependent on that of precursor random alloy nanocrystals 65,66 …”