Structural and architectural evaluation of bimetallic nanoparticles: a case study of Pt-Ru core-shell and alloy nanoparticles.
A comprehensive structural/architectural evaluation of the PtRu (1:1) alloy and Ru@Pt core-shell nanoparticles (NPs) provides spatially resolved structural information on sub-5 nm NPs. A combination of extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), pair distribution function (PDF) analyses, Debye function simulations of X-ray diffraction (XRD), and field emission transmission electron microscopy/energy dispersive spectroscopy (FE-TEM/EDS) analyses provides complementary information used to construct a detailed picture of the core/shell and alloy nanostructures. The 4.4 nm PtRu (1:1) alloys are crystalline homogeneous random alloys with little twinning in a typical face-centered cubic (fcc) cell. The Pt atoms are predominantly metallic, whereas the Ru atoms are partially oxidized and are presumably located on the NP surface. The 4.0 nm Ru@Pt NPs have highly distorted hcp Ru cores that are primarily in the metallic state but show little order beyond 8 A. In contrast, the 1-2 monolayer thick Pt shells are relatively crystalline but are slightly distorted (compressed) relative to bulk fcc Pt. The homo- and heterometallic coordination numbers and bond lengths are equal to those predicted by the model cluster structure, showing that the Ru and Pt metals remain phase-separated in the core and shell components and that the interface between the core and shell is quite normal.
Alayoglu
Selim
S
Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
Zavalij
Peter
P
Eichhorn
Bryan
B
Wang
Qi
Q
Frenkel
Anatoly I
AI
Chupas
Peter
P
D000497:Alloys / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010084:Oxidation-Reduction; D010316:Particle Size; D010984:Platinum / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy; D014961:X-Ray Diffraction
D000497:Alloys; D010984:Platinum; D012428:Ruthenium