Generation of Pd Model Catalyst Nanoparticles by Spark Discharge

Messing, Maria E.; Westerström, Rasmus; Meuller, Bengt; Blomberg, Sara; Gustafson, Johan; Andersen, Jesper N; Lundgren, Edvin; Rijn, Richard M. van; Balmès, Olivier; Bluhm, Hendrik; Deppert, Knut

doi:10.1021/jp101390a

Cited by 35 publications

(25 citation statements)

References 30 publications

(46 reference statements)

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“…As reported in Ref. [34], the resulting samples are highly carbon contaminated and the Pd nanoparticles are covered by a shell of Pd carbide. This contamination can be removed through oxidation.…”

Section: Methodsmentioning

confidence: 83%

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Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

et al. 2011

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Using in situ high pressure X-ray photoelectron spectroscopy (HPXPS), we have followed the oxidation and the reduction of Pd model catalysts in oxygen and CO pressures in the mbar range. The study includes a Pd(100) single crystal as well as SiOx supported Pd nanoparticles of 15 or 35 nm diameter respectively. We demonstrate that also nanoparticles form ultra-thin surface oxides prior to the onset of the bulk PdO. The Pd nano particles are observed to bulk oxidize at sample temperatures 40 degrees lower than the single crystal surface. In the Pd 3d 5/2 and the O 1s spectrum we identify a component corresponding to under-coordinated atoms at the surface of the PdO oxide. The experimentally observed PdO CLS is supported by density functional theory calculations (DFT). In a CO atmosphere, the Pd 3d 5/2 component corresponding to under-coordinated PdO atoms is shifted by +0.55 eV with respect to PdO bulk, demonstrating that CO molecules preferably adsorbs at these sites. CO coordinated to Pd atoms in the metallic and the oxidized phase can also be distinguished in the C 1s spectrum. The initial reduction by CO is similar for the single crystal and the nanoparticle samples, but after the complete removal of the oxide we detect a significant deviation between the two systems, namely that the nanoparticles incorporate carbon to form a Pd carbide. Our results indicates that CO can dissociate on the nanoparticle samples, whereas no such behavior is observed for the Pd(100) single crystal. These results demonstrate the similarities, as well as the important differences, between the single crystal used as model systems for catalysis and nm sized particles on oxide supports.

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Section: Methodsmentioning

confidence: 83%

“…[34]. In brief, areosol Pd particles were size selected and deposited onto a Si wafer that has been cleaned by HF etching and brought out in air in order to grow a native SiO x oxide.…”

Section: Methodsmentioning

confidence: 99%

Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

et al. 2011

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“…Another gas-phase method for the production of metal nanoparticles is spark generation, where particles are produced from the electrode material by sublimation (Messing et al 2009;Messing et al 2010;Tabrizi et al 2009). Spark generation of nanoparticles is most commonly achieved by repeatedly discharging a current between two electrodes composed of a metal of interest.…”

Section: Introductionmentioning

confidence: 99%

Hot-Wire Synthesis of Gold Nanoparticles

Boies

Lei

Calder

et al. 2011

Aerosol Science and Technology

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Gold nanoparticles were synthesized by a hot-wire generator at atmospheric pressure using a gold-platinum composite wire. At low gas flow velocities the nanoparticles were found to be agglomerates of partially sintered primary particles. By reducing the tube size via the insertion of a nozzle with a throat diameter of 3 mm, the hot-wire generator was found to produce small (<10 nm diameter) crystalline gold particles. Elemental and x-ray photoelectron spectroscopy analysis of the particles showed that they were composed of gold with no platinum impurity. Charging analysis of the "as-produced" nanoparticles showed that fewer than 10% of the particles were charged, but the charge fraction increased as the applied power increased, as did the ratio of negatively-topositively-charged particles.

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“…This sample has been produced ex-situ by a sparkdischarge method. 27 Ex-situ sample preparation gives additional flexibility, for example, this spark-discharge method produces particles with a well-defined size, but it adds the risk of introducing contaminations during sample transfer. Even though the lateral dimensions of the images of the particles are influenced by the shape of the tip-a common problem with AFM 28 -these images directly give unique information on the particle morphology and size distribution under catalytic conditions.…”

Section: A Imagingmentioning

confidence: 99%

The ReactorAFM: Non-contact atomic force microscope operating under high-pressure and high-temperature catalytic conditions

Roobol

Cañas‐Ventura

Bergman

et al. 2015

Review of Scientific Instruments

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An Atomic Force Microscope (AFM) has been integrated in a miniature high-pressure flow reactor for in-situ observations of heterogeneous catalytic reactions under conditions similar to those of industrial processes. The AFM can image model catalysts such as those consisting of metal nanoparticles on flat oxide supports in a gas atmosphere up to 6 bar and at a temperature up to 600 K, while the catalytic activity can be measured using mass spectrometry. The high-pressure reactor is placed inside an Ultrahigh Vacuum (UHV) system to supplement it with standard UHV sample preparation and characterization techniques. To demonstrate that this instrument successfully bridges both the pressure gap and the materials gap, images have been recorded of supported palladium nanoparticles catalyzing the oxidation of carbon monoxide under high-pressure, high-temperature conditions.

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Generation of Pd Model Catalyst Nanoparticles by Spark Discharge

Cited by 35 publications

References 30 publications

Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

Oxidation and reduction of Pd(100) and aerosol-deposited Pd nanoparticles

Hot-Wire Synthesis of Gold Nanoparticles

The ReactorAFM: Non-contact atomic force microscope operating under high-pressure and high-temperature catalytic conditions

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