X-Ray Absorption Fine Structure Analysis of Catalytic Nanomaterials

Chun, Wang‐Jae; Takakusagi, Satoru; Uemura, Yohei; Bando, Kyoko K.; Asakura, Kiyotaka

doi:10.1007/978-3-662-48606-1_11

Cited by 1 publication

(2 citation statements)

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“…Here, we address a simple question: Why does the Pt–Pt distance in the PtAu nanoparticles contract, whereas the Pt–Pt distance in a Pt monolayer on a Au(111) surface does not? Bond-length contraction has been reported for various metal nanoparticles. − Although Kaito et al found that the Au–Au bond length in the Au core of PtAu nanoparticles was contracted by 0.04 Å to a value of 2.82 Å, this is still longer than the Pt–Pt bond length in bulk Pt (2.76 Å). If the surface-layer bond length (Pt–Pt) strongly depends on the bond length in the substrate (Au–Au), as it does in the case of a flat surface, then the Pt–Pt distance should be elongated because of the effect of the Au core.…”

Section: Introductionmentioning

confidence: 99%

“…Metal nanoparticles exhibit unique electronic properties, such as discrete energy levels and magic number stability originating from quantum mechanics and a high surface/volume ratio . Unique nanoparticle shapes grown from icosahedra, decahedra, and plane triangles have been stabilized to give twin structures. , Lattice contraction − and expansion, , and negative thermal expansion, have been reported for nanoparticles. Such characteristics of nanoparticles make them useful in numerous applications, including catalysis, photocatalysis, and magnetic and electronic devices…”

Section: Introductionmentioning

confidence: 99%

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Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: In Situ Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition

Bharate

Jiménez

et al. 2022

J. Phys. Chem. C

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To reveal the origin of the difference between the Pt−Pt bond distance in Au(core)−Pt(shell)-type (PtAu) nanoparticles and that in a Pt overlayer on Au(111), alloy-type PtAu nanoparticles were prepared on a highly oriented pyrolytic graphite (HOPG) surface by arc plasma deposition and their structure was investigated under various electrochemical conditions by bentcrystal Laue analyzer (BCLA)-empowered back-illuminated X-ray absorption fine structure (BCLA + BI-XAFS) and high-energyresolution fluorescence detection (HERFD)-empowered backilluminated X-ray absorption near-edge structure (HERFD + BI-XANES) methods. On the basis of the XAFS analysis at both edges, we proposed the formation of a PtAu alloy core covered with a Pt-rich shell at 0.4 V RHE , where the Pt−Pt, Pt−Au, and Au− Au bond lengths were all found to be ∼2.76 Å. The Au−Au bond length was abnormally shorter than that for bulk Au. The Pt shell was dissolved under applied potentials greater than 0.8 V RHE with the aid of the high-intensity X-rays, and the Au−Au distance increased. We concluded that the abnormal bond lengths were due to the strong surface tension from the Pt-rich shell and the relaxation of the lattice distortion. The Pt−Pt bond length in the PtAu nanoparticles decreases as a result of the surface tension of the nanoparticles; this surface tension does not exist on flat Au surfaces, where the lattice distortion between the Pt overlayer and the substrate is the main driving force for the expansion of the Pt−Pt bond length.

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