In situ study of atomic structure transformations of Pt-Ni nanoparticle catalysts during electrochemical potential cycling

Xenia Tuaev, Stefan Rudi, Valeri Petkov, Armin Hoell, Peter Strasser

Research output: Contribution to journalArticlepeer-review

88 Scopus citations

Abstract

When exposed to corrosive anodic electrochemical environments, Pt alloy nanoparticles (NPs) undergo selective dissolution of the less noble component, resulting in catalytically active bimetallic Pt-rich core-shell structures. Structural evolution of PtNi6 and PtNi3 NP catalysts during their electrochemical activation and catalysis was studied by in situ anomalous small-angle X-ray scattering to obtain insight in element-specific particle size evolution and time-resolved insight in the intraparticle structure evolution. Ex situ high-energy X-ray diffraction coupled with pair distribution function analysis was employed to obtain detailed information on the atomic-scale ordering, particle phases, structural coherence lengths, and particle segregation. Our studies reveal a spontaneous electrochemically induced formation of PtNi particles of ordered Au3Cu-type alloy structures from disordered alloy phases (solid solutions) concomitant with surface Ni dissolution, which is coupled to spontaneous residual Ni metal segregation during the activation of PtNi6. Pt-enriched core-shell structures were not formed using the studied Ni-rich nanoparticle precursors. In contrast, disordered PtNi3 alloy nanoparticles lose Ni more rapidly, forming Pt-enriched core-shell structures with superior catalytic activity. Our X-ray scattering results are confirmed by STEM/EELS results on similar nanoparticles.

Original languageEnglish
Pages (from-to)5666-5674
Number of pages9
JournalACS Nano
Volume7
Issue number7
DOIs
StatePublished - Jul 23 2013

Keywords

  • ASAXS
  • PtNi alloys
  • fuel cell catalysis
  • in situ characterization
  • pair distribution function

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