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

Research output: Contribution to journalArticle

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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
Pages (from-to)1032-1044
Number of pages13
JournalChemistry of Materials
Volume30
Issue number3
DOIs
Publication statusPublished - Feb 13 2018

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Alkenes
Olefins
Nanoparticles
Ethylene
Atomic emission spectroscopy
Acetylene
X ray absorption spectroscopy
Toluene
Inductively coupled plasma
Butadiene
Hydrides
Nuclear magnetic resonance spectroscopy
Fourier transform infrared spectroscopy
Mass spectrometry
X ray photoelectron spectroscopy
Metals
Chemical activation
Polarization
Transmission electron microscopy
Oxidation

ASJC Scopus subject areas

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

Cite this

Synthesis of Supported Pd0 Nanoparticles from a Single-Site Pd2+ Surface Complex by Alkene Reduction. / Mouat, Aidan R.; Whitford, Cassandra L.; Chen, Bor Rong; Liu, Shengsi; Perras, Frédéric A.; Pruski, Marek; Bedzyk, Michael J.; Delferro, Massimiliano; Stair, Peter C; Marks, Tobin J.

In: Chemistry of Materials, Vol. 30, No. 3, 13.02.2018, p. 1032-1044.

Research output: Contribution to journalArticle

Mouat, AR, Whitford, CL, Chen, BR, Liu, S, Perras, FA, Pruski, M, Bedzyk, MJ, Delferro, M, Stair, PC & Marks, TJ 2018, 'Synthesis of Supported Pd0 Nanoparticles from a Single-Site Pd2+ Surface Complex by Alkene Reduction', Chemistry of Materials, vol. 30, no. 3, pp. 1032-1044. https://doi.org/10.1021/acs.chemmater.7b04909
Mouat, Aidan R. ; Whitford, Cassandra L. ; Chen, Bor Rong ; Liu, Shengsi ; Perras, Frédéric A. ; Pruski, Marek ; Bedzyk, Michael J. ; Delferro, Massimiliano ; Stair, Peter C ; Marks, Tobin J. / Synthesis of Supported Pd0 Nanoparticles from a Single-Site Pd2+ Surface Complex by Alkene Reduction. In: Chemistry of Materials. 2018 ; Vol. 30, No. 3. pp. 1032-1044.
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AU - Liu, Shengsi

AU - Perras, Frédéric A.

AU - Pruski, Marek

AU - Bedzyk, Michael J.

AU - Delferro, Massimiliano

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AU - Marks, Tobin J

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N2 - 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.

AB - 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.

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