Three-Layer Core/Shell Structure in Au−Pd Bimetallic Nanoparticles

Ferrer, Domingo; Torres–Castro, Alejandro; Gao, Xueqin; Sepúlveda-Guzmán, S.; Ortiz-Méndez, Ubaldo; José–Yacamán, Miguel

doi:10.1021/nl070694a

Cited by 297 publications

(254 citation statements)

References 32 publications

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“…Annealing these clusters up to 450 K, on the other hand, has led to the emergence of an XRD signal at 38.8°, suggesting gradual crystallization of the Pd-Au alloy, as discussed above ( brighter in STEM than palladium clusters as a result of their different atomic numbers. 25,26 Elemental analysis of a single (typical) cluster (along the red line marked in the STEM images) using the STEM-EDX mode revealed the role of preparation mode on clusters composition and shape. Clusters of type A (Figure 3a) include bright spots that are predominantly composed of gold atoms, located on top of dim, elongated palladium clusters (that were deposited first) (Figure 3d).…”

Section: Resultsmentioning

confidence: 99%

Chemical Reactivity of Pd−Au Bimetallic Nanoclusters Grown via Amorphous Solid Water as Buffer Layer

2009

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Bimetallic Pd-Au nanoclusters were prepared on SiO 2 /Si(100) via amorphous solid water (ASW) as buffer layer. Selective growth pathways have led to segregated palladium and gold clusters or alloy bimetallic crystallites. Morphology and chemical composition were determined by AFM, SEM, and HR-TEM coupled to EDX analysis. Correlation between clusters morphology and composition to their chemical reactivity is reported for the first time. Temperature programmed reaction studies revealed that conversion of acetylene to ethylene and trimerization to benzene are significantly enhanced over crystalline alloy Pd-Au clusters when compared to clean Pd. A remarkable selectivity toward ethylene formation over benzene is unique to the alloy bimetallic clusters grown via ASW buffer layer on silica, presumably due to suppression of the trimerization pathway. The intrinsic, modified electronic properties of the bimetallic alloy clusters are believed to drive their enhanced chemical reactivity when compared with the pure Pd clusters.

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Section: Resultsmentioning

confidence: 99%

Chemical Reactivity of Pd−Au Bimetallic Nanoclusters Grown via Amorphous Solid Water as Buffer Layer

2009

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“…16 They exhibit a Pd-rich core, with the first shell highly enriched in Au, and a Pd-rich outer shell. A typical HAADF image of the three-layer Au/Pd particles is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Atomic structure of three-layer Au/Pd nanoparticles revealed by aberration-corrected scanning transmission electron microscopy

et al. 2008

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Aberration-corrected imaging is employed under the scanning transmission electron microscopy (STEM) mode to precisely determine the chemical ordering of Au/Pd nanoparticles. These colloids exhibit a core-shell structure with a three-layer arrangement that surprisingly presents alloying events in the observed layers. Aberration-corrected imaging is employed under the scanning transmission electron microscopy (STEM) mode to precisely determine the chemical ordering of Au/Pd nanoparticles. These colloids exhibit a coreshell structure with a three-layer arrangement that surprisingly presents alloying events in the observed layers. The study of nanomaterials can be greatly improved with the use of aberration-corrected transmission electron microscopy (TEM), which provides image resolutions at the level of 1 Å and lower. Sub-Å ngströ m image resolution can yield a new level of understanding of the behavior of matter at the nanoscale. For example, bimetallic nanoparticles are extremely important in catalysis applications; the addition of a second metal in many cases produces much-improved catalysts. In this paper, we study the structure and morphology of Au/Pd bimetallic particles using primarily the high-angle annular dark-field (HAADF) imaging mode in an aberration-corrected STEM/TEM. It is well established that, when recorded under appropriate illumination and collection geometries, incoherent HAADF-STEM images are compositionally sensitive and provide direct information on atomic positions. We matched the experimental intensities of atomic columns with theoretical models of three-layer Au/Pd nanoparticles, in different orientations. Our findings indicate that the surface layer of the nanoparticle contains kinks, terraces and steps at the nanoscale. The effect of adding a second metal induces the formation of such defects, which might very likely promote the well-known improved catalytic activity of this system.

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“…In many cases random mixed configuration is often called alloyed nanoparticles. Multishell alloys configuration may present layered or onion-like alternating -A-B-A-shells 8,9 . However, one of the most important challenges nowadays is to know the distribution of the elements and the atomic positions in the above-mentioned configurations.…”

Section: Introductionmentioning

confidence: 99%

Study of PtPd Bimetallic Nanoparticles for Fuel Cell Applications

et al. 2017

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Bimetallic nanoparticles are of special interest for their potential applications for fuel cells, mainly for portable power applications. Among the bimetallic systems, Pt-Pd bimetallic nanoparticles have received great interest as they can be widely used as effective catalysts for various electrochemical reactions. In this work, Pt-Pd alloy bimetallic nanoparticles were synthesized through a chemical reduction method. The nanoparticles were characterized using aberration-corrected scanning/transmission electron microscopy (STEM). Also, parallel beam X-Ray diffraction analysis was carried out to evaluate the crystallographic structure. High-angle annular dark field (HAADF)-STEM images of the Pt-Pd bimetallic nanoparticles were obtained. The contrast of the images shows that the nanoparticles have an alloy structure with an average size of 7.15 nm. To understand the properties of the bimetallic nanoparticles, it is necessary to know the distribution of the elements in the nanostructure. We have used a semi-quantitative method to analyze the HAADF-STEM images, which allowed us to measure the total intensity of the scattered electrons for each atomic column. HAADF-STEM images of the Pt-Pd bimetallic nanoparticles were compared directly with image simulations, good agreement between simulation and experimental images was found. Cyclic voltammetry studies were carried out to analyze the electrochemical behavior of the bimetallic nanoparticles.

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Three-Layer Core/Shell Structure in Au−Pd Bimetallic Nanoparticles

Cited by 297 publications

References 32 publications

Chemical Reactivity of Pd−Au Bimetallic Nanoclusters Grown via Amorphous Solid Water as Buffer Layer

Chemical Reactivity of Pd−Au Bimetallic Nanoclusters Grown via Amorphous Solid Water as Buffer Layer

Atomic structure of three-layer Au/Pd nanoparticles revealed by aberration-corrected scanning transmission electron microscopy

Study of PtPd Bimetallic Nanoparticles for Fuel Cell Applications

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