Unusual non-bulk properties in nanoscale materials: Thermal metal-metal bond contraction of γ-alumina-supported Pt catalysts

Joo H. Kang, Laurent D. Menard, Ralph G. Nuzzo, Anatoly I. Frenkel

Research output: Contribution to journalArticlepeer-review

Abstract

Variable-temperature X-ray absorption spectroscopy measurements of sub-nanometer Pt nanoparticles on a high-surface-area γ-alumina support reveal that the Pt-Pt bonds exhibit contraction upon heating [i.e., negative thermal expansion (NTE)]. Bare clusters under a He environment show an average linear expansion coefficient of -2.5 × 10-5 K-1 over the temperature range studied. Adsorption of hydrogen results in an overall bond relaxation and less dramatic Pt-Pt thermal bond-length contraction. From the temperature effect on bond length, disorder parameters, and the X-ray absorption near edge structure (XANES) spectra, temperature-dependent charge transfer between the support and the Pt clusters was concluded to be responsible for the observed behavior.

Original languageEnglish (US)
Pages (from-to)12068-12069
Number of pages2
JournalJournal of the American Chemical Society
Volume128
Issue number37
DOIs
StatePublished - Sep 20 2006

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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