Synthesis of Supported Pd0 Nanoparticles from a Single-Site Pd2+ Surface Complex by Alkene Reduction

Aidan R. Mouat, Cassandra L. Whitford, Bor Rong Chen, Shengsi Liu, Frédéric A. Perras, Marek Pruski, Michael J. Bedzyk, Massimiliano Delferro*, Peter C. Stair, Tobin J. Marks

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

A surface metal-organic complex, (-AlOx)Pd(acac) (acac = acetylacetonate), is prepared by chemically grafting the precursor Pd(acac)2 onto γ-Al2O3 in toluene at 25 °C. The resulting surface complex is characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and dynamic nuclear polarization surface-enhanced solid-state nuclear magnetic resonance spectroscopy (DNP SENS). This surface complex is a precursor in the direct synthesis of size-controlled Pd nanoparticles under mild reductive conditions and in the absence of additional stabilizers or pretreatments. Indeed, upon exposure to gaseous ethylene or liquid 1-octene at 25 °C, the Pd2+ species is reduced to form Pd0 nanoparticles with a mean diameter of 4.3 ± 0.6 nm, as determined by scanning transmission electron microscopy (STEM). These nanoparticles are catalytically relevant using the aerobic 1-phenylethanol oxidation as a probe reaction, with rates comparable to a conventional Pd/Al2O3 catalyst but without an induction period. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature-programmed reaction mass spectrometry (TPR-MS) reveal that the surface complex reduction with ethylene coproduces H2, acetylene, and 1,3-butadiene. This process reasonably proceeds via an olefin activation/coordination/insertion pathway, followed by β-hydride elimination to generate free Pd0. The well-defined nature of the single-site supported Pd2+ precursor provides direct mechanistic insights into this unusual and likely general reductive process.

Original languageEnglish (US)
Pages (from-to)1032-1044
Number of pages13
JournalChemistry of Materials
Volume30
Issue number3
DOIs
StatePublished - Feb 13 2018

ASJC Scopus subject areas

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

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