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In situ XAS and XRF study of nanoparticle nucleation during O3-based Pt deposition

Paper ID Volume ID Publish Year Pages File Format Full-Text
54106 46997 2014 12 PDF Available
Title
In situ XAS and XRF study of nanoparticle nucleation during O3-based Pt deposition
Abstract

•First time in situ XAS and XRF study of ALD-based synthesis of Pt catalysts.•The diameter, shape, packing and density of the deposited Pt clusters are obtained.•The degree of cluster surface oxidation after O3 pulsing is gained quantitatively.•During deposition nucleation dominates initially followed by gradual coalescence.•The synergy of the simultaneous in situ application of XAS and XRF is proven.

X-ray absorption spectroscopy (XAS) and X-ray fluorescence (XRF) were combined in situ to study the ALD-based synthesis of Pt catalysts. This first time combination of synchrotron-based techniques was applied during the (methylcyclopentadienyl)trimethylplatinum/ozone deposition process executed at 150 °C on a silica support. A nucleation delay indicative for nanoparticle formation was observed for Pt loadings below 1 equivalent monolayer. XAS and XRF were recorded simultaneously at different catalyst loadings in this nucleation regime. Analysis of the combined in situ data yielded a quantitative picture of the evolution of the diameter, shape, lattice packing and density of the deposited Pt clusters. Additionally, the degree of oxidation at the cluster surface after the ozone pulse could be monitored. At the early start of the deposition process, Pt adatoms cluster together to form stable nuclei. A strong increase in the density of nuclei is seen below 0.16 equivalent monolayers, after which coalescence gradually occurs. From 0.04 to 0.71 equivalent monolayers, Pt clusters are fcc packed and correspond best to a hemispherical (1 1 1)-truncated cuboctahedral shape. By crosslinking the XRF and XAS data, a linear increase in cluster diameter with Pt loading is observed within this range. The surface of the Pt clusters is shown to be oxidized immediately after the ozone exposure. The degree of surface oxidation remains approximately constant for clusters with a 1–3 nm diameter. This surface oxygen is shown to be crucial for further growth during deposition. The combined application of in situ XRF and XAS thus allowed for an advanced identification of the ALD-deposited Pt nanoparticles.

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Keywords
Ozone-based Pt deposition; Nucleation; In situ characterization; X-ray absorption spectroscopy; X-ray fluorescence; Atomic layer deposition
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In situ XAS and XRF study of nanoparticle nucleation during O3-based Pt deposition
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Today - Volume 229, 15 June 2014, Pages 2–13
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us