Stability of Core-Shell Nanoparticles for Catalysis at Elevated Temperatures: Structural Inversion in the Ni-Au System Observed at Atomic Resolution

Martin Schnedlitz, Maximilian Lasserus, Ralf Meyer, Daniel Knez, Ferdinand Hofer, Wolfgang E. Ernst*, Andreas W. Hauser

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

We present in situ transmission electron microscopy (TEM) studies of nanoscale Ni-Au core-shell particles on heatable TEM grids. The bimetallic clusters, grown fully inert within superfluid helium nanodroplets to avoid any template or solvent effects, are deposited on amorphous carbon and monitored through a heating cycle from room temperature to 400 °C and subsequent cooling. Diffusion processes, known to impair the catalytic activities of core-shell structures, are studied as a function of the temperature and quantified through fits of a temperature-dependent diffusion constant directly derived from the experiment. After cooling, spatially resolved energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy measurements prove the inversion of the core-shell structure from Ni-Au to Au-Ni. Furthermore, a strong oxidation of the now exposed Ni shell is observed in the latter case. In combination with theoretical studies employing density functional theory, we analyze the influence of oxygen on the observed intermetallic diffusion.

Original languageEnglish
Pages (from-to)1113-1120
Number of pages8
JournalChemistry of Materials
Volume30
Issue number3
DOIs
Publication statusPublished - 13 Feb 2018

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

Fields of Expertise

  • Advanced Materials Science

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