Published on Web 11/24/2009
A General Strategy for Preparation of Pt 3d-Transition Metal
(Co, Fe, Ni) Nanocubes
Jun Zhang and Jiye Fang*
Department of Chemistry, State UniVersity of New York at Binghamton,
Binghamton, New York 13902
Received October 5, 2009; E-mail: jfang@binghamton.edu
Abstract: A facile, reliable, general, and robust synthetic method for preparation of high-quality, (100)-
terminated Pt3M nanocubes (M ) Pt or 3d-transition metals Co, Fe, and Ni) has been developed. It was
identified that addition of W(CO)6 is crucial for control of the nucleation process when the metallic precursors
are reduced, whereas an optimized ratio of the solvent pair, oleylamine and oleic acid, is the key to enabling
the lowest total surface energy on {100} facets in order to develop cubic nanocrystals in the present system.
The resultant monodisperse nanocubes, in which Pt is partially substituted, are expected to exhibit unusual
electrocatalytic characteristics, providing an alternative for developing high-performance electrocatalysts
for use in fuel cells.
Introduction
natures. In order to enhance catalytic performance while
minimizing the use of precious metal Pt, it is worthwhile to
The precious metal platinum is traditionally used as a high-
performance electrocatalyst for proton-exchange membrane fuel
cells and fine chemical synthesis.1 Due to the high cost and the
scarcity of Pt, it is an urgent task to develop substitutes for the
pure Pt catalyst. To date, one of the most successful alternatives
has involved partially substituting Pt using less expensive 3d-
transition metals.1-8 It has also been recognized that the shape
and surface structure of nanocrystals (NCs) play significant roles
in electrocatalytic activity9-11 and reaction durability.4,12 For
instance, it has been reported that cubic Pt NCs possess unusual
catalytic activity in oxidation reactions.1,13 As is well-known,
the electron density of states is actually sensitive to the surface
structure, and different crystal facets could have diverse catalytic
prepare various shape-controlled nano-polyhedra containing Pt
and 3d-transition metals, such as {100}-terminated nanocubes
and {111}-bounded nano-octohedra, and to experimentally
survey the catalytic characteristics of various crystal facets on
each binary alloy. Unfortunately, there is still no general strategy
to fabricate shape-controlled nano-polyhedra of Pt-based alloys,
although syntheses of pure Pt1,14-16 and PtFe17 nanocubes
(NCbs) have recently been demonstrated.
In this article, we report a novel, robust, and general approach
to the synthesis of monodisperse and high-yield NCbs of Pt
and Pt-based binary alloys containing a relatively broad
spectrum of 3d-tranistion metals. The unique aspects of this
new synthetic strategy are the control of both the nucleation
process and the subsequent crystal growth stage by using
tungsten hexacarbonyl [W(CO)6] and the ability to tune the
total surface energies on various crystal facets in solution
by altering their binding-agent capability (Vide infra). Specif-
ically, reduction of platinum(II) acetylacetonate [Pt(acac)2]
produces Pt NCbs, whereas co-reduction of Pt(acac)2 and a
metal salt (M ) Co, Fe, or Ni)sthat is, cobalt acetate
tetrahydrate (CoAc2 · 4H2O), iron(II) chloride tetrahydride
(FeCl2 · 4H2O), or nickel(II) chloride hexahydride (NiCl2 ·
6H2O)sgenerates Pt3Co, Pt3Fe, or Pt3Ni NCbs.
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Experimental Section
NCbs of Pt3M (M ) Pt, Co, Fe, and Ni) were systematically
prepared through a general approach in which a co-reduction of
platinum(II) acetylacetonate [Pt(acac)2] and M-salt in a mixed
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9
10.1021/ja908245r 2009 American Chemical Society
J. AM. CHEM. SOC. 2009, 131, 18543–18547 18543