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Rapid and Surfactant-Free Synthesis of Bimetallic Pt–Cu Nanoparticles Simply via Ultrasound-Assisted Redox Replacement
journal contribution
posted on 2012-08-03, 00:00 authored by Zhenyu Sun, Justus Masa, Wei Xia, Dennis König, Alfred Ludwig, Zi-An Li, Michael Farle, Wolfgang Schuhmann, Martin MuhlerThe synthesis of bimetallic nanoparticles (NPs) with
well-defined
morphology and a size of <5 nm remains an ongoing challenge. Here,
we developed a facile and efficient approach to the design of bimetallic
nanostructures by the galvanic replacement reaction facilitated by
high-intensity ultrasound (100 W, 20 kHz) at low temperatures. As
a model system, Pt–Cu NPs deposited on nitrogen-doped carbon
nanotubes (NCNTs) were synthesized and characterized by spectroscopic
and microscopic techniques. Transmission electron microscopy (TEM)
inspection shows that the mean diameter of Pt–Cu NPs can be
as low as ≈2.8 nm, regardless of the much larger initial Cu
particle size, and that a significant increase in particle number
density by a factor of 35 had occurred during the replacement process.
The concentration of the Pt precursor solution as well as of the size
of the seed particles were found to control the size of the bimetallic
NPs. Energy dispersive X-ray spectroscopy performed in the scanning
TEM mode confirmed the alloyed nature of the Pt–Cu NPs. Electrochemical
oxygen reduction measurements demonstrated that the resulting Pt–Cu/NCNT
catalysts exhibit an approximately 2-fold enhancement in both mass-
and area-related activities compared with a commercial Pt/C catalyst.
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Keywords
bimetallic nanoparticlesalloyed natureElectrochemical oxygen reduction measurements20 kHzseed particlesCu particle sizereplacement processreplacement reactionbimetallic NPsNCNTtransmission electron microscopyscanning TEM modePt precursor solutionbimetallic nanostructuresmodel systemparticle number density
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