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Pt-Ru Bulk Phase Diagram - PowerPoint PPT Presentation


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Pt-Ru Bulk Phase Diagram. H 2. +. 673 K. Supported Metal Nanoparticle. Metal Salt Precursor. ?. Pt/C + RuCl 3 •3H 2 O. [Pt x Ru y ]/C. Ru/C + H 2 PtCl 6 • x H 2 O. [Pt x Ru y ]/C. Ru/C + (CH 3 ) 2 Pt(COD). [Pt x Ru y ]/C. Nanoscale Phase Behavior.

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Presentation Transcript
slide2

H2

+

673 K

Supported Metal Nanoparticle

Metal Salt Precursor

?

Pt/C + RuCl3•3H2O

[PtxRuy]/C

Ru/C + H2PtCl6•xH2O

[PtxRuy]/C

Ru/C + (CH3)2Pt(COD)

[PtxRuy]/C

Nanoscale Phase Behavior

Characterization of final nanoparticles:

X-ray Photoelectron Spectroscopy (XPS)

Scanning Transmission Electron Microscopy (STEM)

Energy Dispersive X-ray Analysis (EDAX)

Electron Microdiffraction

slide3

Ru3d

Ru3d

Pt4f

Pt4f

N(E)/E

N(E)/E

Binding Energy (eV)

Binding Energy (eV)

X-ray Photoelectron Spectroscopy (XPS)

X-Ray Photoelectron Spectroscopy (XPS) probes the composition of the bulk sample. These figures show that bimetallic nanoparticles are formed upon reduction of a a metallic salt in the presence of supported nanoparticles (Ru or Pt).

slide4

Dark field micrograph of 10% Ru/Carbon Black (ETEK) after addition of H2PtCl6, followed by reduction.

Dark field micrograph of 10% Ru/Carbon Black (ETEK).

Growth of Nanoparticles after Reduction

slide5

10 % Pt/C

Relative Abundance

10% Pt/C + RuCl3

Relative Abundance

Particle Size (Å)

Particle Size Distribution:

Ru + Pt/C

slide6

Cu

Ru

Ru

nanoparticle

Pt

Pt

Cu

carbon support

Compositional Analysis:

Energy Dispersive X-ray Analysis (EDAX)

Relative Abundance

Atomic Composition (at.% Ru)

Using EDAX, the composition of individual particles is probed. The figure on the left shows sample EDAX spectra for both the carbon support and a particle of ca. 80 % Ruthenium. The figure on the right shows the representative composition distribution for all bimetallic samples.

slide7

A

A

B

B

C

A

A

B

B

A

C

B

A

A

Hexagonal Closest Packed (hcp)

Face Centered Cubic (fcc)

Atomic Ordering in Solids

Adapted from: http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch13/structureframe.html

slide8

111

Model XRD of Pt (fcc)

420

311

331

200

220

222

400

Model XRD of Ru (hcp)

10-11

11-22

0002

10-13

10-10

20-23

11-20

20-21

10-12

21-30

20-22

10-14

20-20

0004

Sample X-Ray Diffraction Patterns

Intensity

Intensity

2  (deg)

slide9

[011]

[0001]

[011]

Electron Microdiffraction

66 Å particle with a composition of 16% Ru

35 Å particle with a composition of 66% Ru

41 Å particle with a composition of 42% Ru

slide10

Particle Size (Å)

Particle Size (Å)

Particle Size (Å)

Atomic Composition (% Ru)

Atomic Composition (% Ru)

Template Effects in the Binary Phase Diagram of Pt-Ru Nanoparticles

“Nano”-phase diagram of bimetallic particles formed on supported Ru clusters.

“Nano”-phase diagram of bimetallic particles formed on supported Pt clusters.

slide11

Particle Size (Å)

Atomic Composition (% Ru)

Binary Nano-Phase Diagram

  • Supported bimetallic nanoparticles can be synthesized by reducing metallic salts onto pre-existing metallic nanoparticles.
  • XPS, EDAX, and STEM provide evidence of the formation of bimetallic particles with wide size and compositional distributions.
  • These bimetallic nanoparticles have an organized close-packed structure that shows phase-sensitive behavior across the compositional space. Microdiffraction results show template effects via the coexistence of both (fcc) and (hcp) structures within the same samples.