Pt-Ru Bulk Phase DiagramPt-Ru Bulk Phase Diagram

+ H2

673 K

?Supported Metal Nanoparticle Metal Salt Precursor

Characterization of final nanoparticles:X-ray Photoelectron Spectroscopy (XPS)Scanning Transmission Electron Microscopy (STEM)Energy Dispersive X-ray Analysis (EDAX)Electron Microdiffraction

Nanoscale Phase BehaviorNanoscale Phase Behavior

Pt/C + RuCl3•3H2ORu/C + H2PtCl6•xH2O

[PtxRuy]/C

[PtxRuy]/C

Ru/C + (CH3)2Pt(COD) [PtxRuy]/C

X-ray Photoelectron Spectroscopy (XPS)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).

Binding Energy (eV)

N(E

)/E

Ru3dPt4f

Binding Energy (eV)N

(E)/E

Ru3d

Pt4f

Growth of Nanoparticles after ReductionGrowth of Nanoparticles after Reduction

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).

Particle Size Distribution:Particle Size Distribution:Ru + Pt/CRu + Pt/C

Rel

ativ

e A

bund

ance

Rel

ativ

e A

bund

ance

Particle Size (Å)

10 % Pt/C

10% Pt/C + RuCl3

Compositional Analysis: Compositional Analysis: Energy Dispersive X-ray Analysis (EDAX)Energy Dispersive X-ray Analysis (EDAX)

Cu

Ru Cu

PtRunanoparticle

carbon support

Pt

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.

Atomic Composition (at.% Ru)

Rel

ativ

e A

bund

ance

A

B

C

A

B

B

B

B

A

A

A

C

A

A

Hexagonal Closest Packed (hcp)Face Centered Cubic (fcc)

Atomic Ordering in SolidsAtomic Ordering in Solids

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

Model XRD of Pt (fcc)

420

400

331

222

311

22020

0

111

Model XRD of Ru (hcp)

20-2

010-1

3

11-2

0

10-1

2

10-1

100

0210

-10

10-1

4

20-2

200

0420

-21

11-2

2

21-3

020-2

3

Sample X-Ray Diffraction PatternsSample X-Ray Diffraction Patterns

2 (deg)

Inte

nsi ty

Inte

nsi ty

Electron MicrodiffractionElectron Microdiffraction

[011]

[0001] [011]

41 Å particle with a composition of 42% Ru

66 Å particle with a composition of 16% Ru 35 Å particle with a composition of 66% Ru

Parti

cle

Size

(Å)

Atomic Composition (% Ru)

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

Parti

cle

Size

(Å)

Atomic Composition (% Ru)

Parti

cle

Size

(Å)

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

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

Binary Nano-Phase DiagramBinary 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.Atomic Composition (% Ru)

Parti

cle

Size

(Å)