Synthesis of Core@Shell Cu-Ni@Pt-Cu Nano-Octahedra and Their Improved MOR Activity

Article abstract of DOI:10.1002/anie.202014144

Fabrication of 3d metal-based core@shell nanocatalysts with engineered Pt-surfaces provides an effective approach for improving the catalytic performance. The challenges in such preparation include shape control of the 3d metallic cores and thickness control of the Pt-based shells. Herein, we report a colloidal seed-mediated method to prepare octahedral CuNi@Pt-Cu core@shell nanocrystals using CuNi octahedral cores as the template. By precisely controlling the synthesis conditions including the deposition rate and diffusion rate of the shell-formation through tuning the capping ligand, reaction temperature, and heating rate, uniform Pt-based shells can be achieved with a thickness of <1 nm. The resultant carbon-supported CuNi@Pt-Cu core@shell nano-octahedra showed superior activity in electrochemical methanol oxidation reaction (MOR) compared with the commercial Pt/C catalysts and carbon-supported CuNi@Pt-Cu nano-polyhedron counterparts.

Full text of DOI:10.1002/anie.202014144

Angewandte
Communications
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How to cite: Angew. Chem. Int. Ed. 2021, 60, 7675–7680
International Edition: doi.org/10.1002/anie.202014144
German Edition: doi.org/10.1002/ange.202014144
Nanocatalysis
Synthesis of Core@Shell Cu-Ni@Pt-Cu Nano-Octahedra and Their
Improved MOR Activity
Can Li, Xiaobo Chen, Lihua Zhang, Shaohui Yan, Anju Sharma, Bo Zhao, Amar Kumbhar,
Guangwen Zhou, and Jiye Fang*
Abstract: Fabrication of 3d metal-based core@shell nano-
catalysts with engineered Pt-surfaces provides an effective
approach for improving the catalytic performance. The
challenges in such preparation include shape control of the
3d metallic cores and thickness control of the Pt-based shells.
Herein, we report a colloidal seed-mediated method to prepare
octahedral CuNi@Pt-Cu core@shell nanocrystals using CuNi
octahedral cores as the template. By precisely controlling the
synthesis conditions including the deposition rate and diffusion
rate of the shell-formation through tuning the capping ligand,
reaction temperature, and heating rate, uniform Pt-based shells
can be achieved with a thickness of < 1 nm. The resultant
carbon-supported CuNi@Pt-Cu core@shell nano-octahedra
showed superior activity in electrochemical methanol oxida-
tion reaction (MOR) compared with the commercial Pt/C
catalysts and carbon-supported CuNi@Pt-Cu nano-poly-
hedron counterparts.
blocking the commercialization.[2] Nevertheless, Pt-based
nanomaterials are the best electrocatalysts for promoting
both the cathodic reaction (oxygen reduction reaction, ORR)
and anodic reactions (oxidation of hydrogen and small
molecular hydrocarbons such as methanol, ethanol, and
formic acid).[3] In this regard, there have been considerable
efforts on the design and development of novel-structure
catalysts to reduce the utilization of Pt and to improve the
electrocatalytic performance.[4]
Current efforts on improving the Pt-based fuel cell
catalysts can be outlined in three strategies: alloying Pt with
another metal such as a 3d transition element (e.g. Cu, Ni, Co,
and Fe),[5] tailoring desirable crystallographic facets on the
catalyst surfaces,[6] and structure/composition manipulation
(e.g. core@shell fabrication) with an alternation of surface
lattice strains.[4b,7] For example, M@Pt-Ni core@shell nano-
structures have been synthesized using a seed-mediated
method, in which a non-Pt noble metal (M) acts like the
seeds and Pt-based alloy as the shells.[8] This design could not
only decrease the usage of Pt significantly but also improve
the electrocatalytic performance by creating the surface strain
(compressive or tensile strain) effect that arises from the
lattice mismatch at the interface between the core and shell
through tuning the shell thickness.[4d,9] As a further improve-
ment in the synthesis, strategies of crystallographic plane
control and core@shell scheme were combined to strengthen
the surface function of well-defined Pt facets. For instance,
Xia et al. have successfully coated an ultrathin Pt layer on
morphology-controlled Pd nanocrystals such as Pd nano-
cubes,[7c] nano-octahedra,[7c,9b] and nano-icosahedra.[7d] Since
the Pt thin-layer is grown on the Pd(111) surface, the epitaxial
strain in the Pt(111) shell can be manipulated to favorably
I
n comparison with a heat engine that converts thermal
energy of fossil fuels to mechanical energy via the Carnot
cycle, a fuel cell device can lead to exciting performance
improvements for power generation by directly converting
the chemical energy of a fuel into electricity. The intense
interest in fuel cell technology stems from the fact that fuel
cells are environmentally benign and extremely efficient (40–
70% efficiency by far).[1] Although this energy conversion
strategy has been well developed and some of the commercial
fuel cell products have been already available, there are still
several issues and challenges associated with the fuel cell
catalysts. For proton-exchange membrane fuel cells
(PEMFCs), the slow kinetics of reactions on electrodes and
the high cost of Pt electrocatalysts are still the main obstacles
[*] C. Li, Dr. S. Yan, Prof. Dr. J. Fang
Department of Chemistry
Dr. B. Zhao
College of Arts & Sciences Microscopy
Texas Tech University
State University of New York at Binghamton
Binghamton, NY 13902 (USA)
Lubbock, TX 79409 (USA)
E-mail: jfang@binghamton.edu
Dr. A. Kumbhar
X. Chen, Prof. Dr. G. Zhou, Prof. Dr. J. Fang
Materials Science and Engineering Program
State University of New York at Binghamton
Binghamton, NY 13902 (USA)
Chapel Hill Analytical and Nanofabrication Laboratory
University of North Carolina at Chapel Hill
Chapel Hill, NC 27599 (USA)
Dr. S. Yan
Dr. L. Zhang
Present address: College of Environmental Science and Engineering
Taiyuan University of Technology
Taiyuan, Shanxi Province (China)
Center for Functional Nanomaterials
Brookhaven National Laboratory
Upton, NY 11973 (USA)
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202014144.
Dr. A. Sharma
Analytical and Diagnostics Lab
State University of New York at Binghamton
Binghamton, NY 13902 (USA)
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alter the bonding energy between the relevant reaction
species and the Pt surface sites. These shape-controlled
core@shell nano-architectures demonstrated much enhanced
ORR performance.[7c,d,9b] However, the lattice parameter
differences among the selected noble metals (the core and
the shell) are still not large enough to result in sufficient
lattice mismatch and strain effect (e.g., Pd-Pt, the lattice
parameter difference fr < 1%). Consequently, synthesis of
shape-controlled core@shell nanostructures with large fr
(generally, fr > 5%) still remains a challenge.[4a,h,9c]
Figure 1. a) TEM image of CuNi nano-octahedra. b) High-resolution
TEM of a typical CuNi nano-octahedron along the zone axis of [011];
Inset is the corresponding Fast Fourier Transform pattern of the
HRTEM image.
Based on these developments, in this work, we replaced
the noble metal cores using 3d transition alloy (CuNi)
nanocrystals (NCs) that are terminated with {111} facets to
increase the core@shell lattice mismatch. Moreover, in this
novel nano-architecture (designed as “CuNi@Pt-Cu nano-
octahedra”), our structural characterization suggested a thin
layer of Pt-Cu alloy as the shell, instead of the pure Pt. Such
structures after a carbon loading treatment (designed as
“CuNi@Pt-Cu nano-octahedra/C”) would further improve
the catalytic performance. As a counterpart, a similar nano-
architecture was also comparatively synthesized without
a shape control (designed as “CuNi@Pt-Cu nano-poly-
hedra”), carbon-loaded (designed as “CuNi@Pt-Cu nano-
polyhedra/C”), and characterized.
To fabricate CuNi@Pt-Cu core@shell nanocatalysts, CuNi
nano-octahedra as the seeds were prepared in the first step,
followed by a Pt-based shell formation in a colloidal system.
The entire preparation procedure is illustrated in Scheme 1.
In a typical synthesis, CuNi octahedra were pre-synthesized
by co-reducing 13.0 mg of copper(II) acetylacetonate and
13.0 mg of nickel(II) acetylacetonate using a borane morpho-
line solution at 2308C in a colloidal system containing
oleylamine, oleic acid, and diphenyl ether.[10] The detailed
preparation is given in Supporting Information. Figure 1a
shows a representative transmission electron microscopy
(TEM) image of the shape-controlled CuNi octahedra.
Their self-assembly further indicated the high quality in
terms of size and shape.[11] Based on the TEM image, the
average size of the CuNi NCs was measured as 13.0 Æ 1.0 nm,
with a uniform distribution of octahedral particles. Figure 1b
is a high-resolution TEM image of a selected individual CuNi
NC along the [011] zone axis. It presents the CuNi crystallo-
graphic fine structure with a (111) lattice spacing of 0.21 nm.
This value is consistent with the (111) lattice spacing
determined from the powder XRD pattern of CuNi nano-
octahedra previously.[10b,c] The HAADF-STEM image and
corresponding energy dispersive X-ray (EDX) elemental
mapping are presented in Figure S1A–D. Unlike the previous
report,[10a] the CuNi octahedron showed a heterogeneous
elemental distribution according to the EDX elemental
mapping. The elemental analysis indicates that the inner
core is dominated by Cu whereas the outer region shows
a uniform distribution of Cu and Ni, leading to a core@shell
structure. This may arise from the modified synthesis
condition in this work. For example, one of the modifications
in the present work was to choose a lower nucleation
temperature (230 vs. 2408C) in the “hot injection” process
when the reducing reagent solution was introduced.[10] The
formation of a heterogeneous structure in CuNi nano-
octahedra is also due to the reduction potential difference
of the precursors at a low temperature. The reduction
potential of Ni2+/Ni0 (À0.26 V vs. RHE) is more negative
than that of Cu2+/Cu0 (+ 0.34 V vs. RHE) (room temperature
data). Therefore Cu2+ would be reduced first, generating Cu-
based nuclei at the initial stage. Once such seeds were yielded,
the further reduced Ni and Cu atoms would epitaxially grow
on the Cu-based seeds easily and result in Cu-Ni alloy as the
outer component. In the bulk of NCs, the average Cu fraction
was determined as ꢀ 52 at% based on the analysis of
inductively coupled plasma-optical emission spectroscopy
(ICP-OES), which is well consistent with the STEM-EDX
result ( ꢀ 51 at%) (Table S1).
Followed by the successful synthesis of the CuNi nano-
octahedra as the core components, CuNi@Pt-Cu core@shell
nanocatalysts were prepared in tandem as illustrated in
Scheme 1. The Pt-based shell growth was carried out by
introducing PtCl4 into the CuNi colloidal system at 608C and
was stirred for ꢀ30 min to generate a uniform mixture under
Argon (Ar) gas protection (for the details see the Supporting
Information). Since the temperature and the Pt reducing rate
are the key factors in this process,[9c] precise control of the
deposition rate and diffusion rate is crucial to the successful
formation of the core@shell CuNi@Pt-Cu nano-octahedra.
Figure 2a is a TEM image of the as-prepared CuNi@Pt-Cu
core@shell nano-octahedra with an average size of 13.3 Æ
1.2 nm. The octahedral core@shell nanostructure was also
imaged using HAADF-STEM (Figure 2b,c) and EDX ele-
mental mapping (Figure S1E–I), respectively. EDX elemental
mapping reveals a core@shell octahedral structure, indicating
that Pt atoms are mainly located on the surface while the
interior consists of Cu-Ni alloy. The Cu- and Ni-EDX
elemental mapping (Figure S1E,F) shows that Cu is still the
Scheme 1. Schematic illustration of the as-synthesized CuNi@Pt-Cu
core@shell nano-octahedra through a seed-mediated process.
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in their shell structure. Compared to Cu in the shell, the
higher Pt contents suggested by XPS possibly indicate that Pt
atoms expose on the shell-surfaces in both samples.
Furthermore, the (111) diffraction peaks of fcc Pt-Cu shell
and fcc Cu-abundant CuNi core can be readily distinguished
in the X-ray diffraction (XRD) patterns of core@shell
CuNi@Pt-Cu nano-octahedra/C as presented in Figure S4.
Compared with the standard ICDD card[14] and previous work
(Table S2),[15] we identified a right-shift at the (111) peak of
the Pt-Cu shell (41.358). This indicates a compressive lattice
strain from the shell induced by the CuNi core that has
a smaller lattice parameter. This effect was also reported in
many core–shell systems previously, such as Au@FePt3,
AgPd@Pt, Ni@FePt, and FePt@Pt NCs.[4b,5d,16] In addition,
the asymmetric shape of the diffraction peak (Figure S4)
further supports the presence of the lattice strain.
Figure 2. a) TEM image of CuNi@Pt-Cu core@shell nano-octahedra.
b) HAADF-STEM image of a typical CuNi@Pt-Cu core@shell nano-
octahedron. c) Crystal structure model of the HAADF-STEM image.
most abundant element in the core center. This is well
consistent with the observation of the CuNi octahedron
(Figure S1B–D). Such a result indicates that the Pt deposition
process mainly occurred on the surface of the CuNi octahe-
dral template whereas the CuNi core kept the same. Based on
these characterizations, no hollow or porous structure was
observed, either. It is, therefore, believed that the Pt-based
shell would protect the CuNi core from etching in the later
evolution stage once it forms. The EDX elemental mapping
further exhibits the presence of Cu signal from the surface
region, implying that the shell component contains both Pt
and Cu elements, instead of a sole Pt constituent. Since the
reduction potential of Ni2+/Ni0 is much lower than those of
Cu2+/Cu0, PtCl4/Pt2+, and Pt2+/Pt0,[12] the reduction of Pt ions
into metallic Pt was most likely achieved through a galvanic
replacement with Ni atoms on the CuNi surface, producing
the CuNi@Pt-Cu core@shell nanostructure. The ICP-OES
composition analysis indicated that the Cu/Ni molar ratio
increased from ꢀ 1.1 (52:48) to ꢀ 2.0 (60:30) after the Pt
deposition (Table S1). Assuming that the content of Cu in the
core was unchanged and no additional Cu atoms were
deposited on the shell during the shell formation process,
the analysis shows a significant decrease of the Ni molar
fraction in the Cu-Ni-based core@shell structure after the
shell formation. This further supports the occurrence of the
Pt4+-Ni0 galvanic replacement reaction during the shell
growth, leading to alloying between the deposited Pt and
the residual Cu on the core surface.
Based on Table S1, the core@shell bulk composition is
Cu60Ni30Pt10. The elemental mapping (Figure S1E–I) further
reveals that the thickness of the Pt-Cu shell is less than 1 nm.
To further identify the near-surface composition, these
samples were also characterized using X-ray photoelectron
spectroscopy (XPS), a surface/near-surface sensitive techni-
que[4i,7a,13] (Figures S2–S3). XPS suggested a composition of
Cu44Ni15Pt41 on the surface/near-surface of CuNi@Pt-Cu
nano-octahedra/C. Compared with the ICP-based (as well
as EDX-based) bulk composition Cu60Ni30Pt10 (or
Cu59Ni31Pt11) presented in Table S1 (note that the average
molar ratio between Cu and Ni in the core is roughly 1:1),
XPS reveals extra Cu on the shell together with Pt, supporting
the binary component in the shell structure. By carefully
examining the elemental fraction of CuNi@Pt-Cu nano-
polyhedra/C determined by XPS (Cu32Ni20Pt48) and ICP
(Cu58Ni30Pt12), one can identify the similar Pt-Cu component
It is worth pointing out that several reaction conditions
are crucial to the success of this shape-controlled core@shell
synthesis. First, optimizing the reaction temperature is
essential to tune the equilibrium between the Pt deposition
rate and diffusion rate during the shell formation stage.
Coinciding with the previous reports,[7c,d,9a,b] we identified that
1808C is a promising temperature, at which reduced Pt atoms
successfully deposited on truncated corners or edges of the
CuNi nano-octahedra and subsequently transferred to their
{111} facets.[6c,9b] Second, the ramp rate of heating plays
a significant role in this shell formation process. We deter-
mined that a slow ramp rate of heating (e.g. 1–28CminÀ1)
favors the well-defined shell growth on the octahedral CuNi
NCs. In contrast, a fast ramp rate of heating (e.g. > 68CminÀ1)
could result in branched structures in the products (refer to
Figure S5). Third, as reported earlier,[10c] chloride ions (ClÀ) as
a kind of capping agents prefer their adsorption on the CuNi
{100} facets (such as the truncated vertices), leading to
a successful “coating” of Pt atoms on the uncapped CuNi
{111} facets. We have alternately re-conducted this shell
growth synthesis in the absence of ClÀ by replacing PtCl4
precursor with Pt(acac)2. As a result, “core-satellite”-like
nanostructures were received as shown in Figure S6. Last, we
noticed that this shell formation process is sensitive to oxygen.
Once the surfaces of CuNi NCs were oxidized, it would be
impossible for Pt atoms to deposit on the CuNi cores and
yield the core@shell nano-architecture. Figure S7 represents
an unfavorable example. With oxidized shells on the CuNi
NCs, Pt atoms would not continuously deposit and grow on
the oxide surface according to the HAADF-STEM EDX
elemental mapping analysis. It is worth pointing out that the
developed CuNi@Pt-Cu nano-octahedra (Figure 2) are more
truncated compared with the CuNi octahedral cores. The
possible reason is that the Cu or Ni atoms located at the
vertices/edges possess higher surface energy. Compared with
the atoms on {111} facets, they are more active to be oxidized
and dissolved into the reaction system. This “etching”-based
development reported previously[17] further validates the
aforementioned hypothesis, that is, the Pt deposition started
from the corners or edges.
To evaluate the electrocatalytic performance of these
nanocatalysts, we carried out a methanol oxidation reaction
(MOR) over the nanocatalysts after a carbon loading treat-
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ment (CuNi@Pt-Cu octahedra/C). The detailed procedure is
described in the Supporting Information. For comparison,
CuNi@Pt-Cu nano-polyhedra/C and a commercial Pt/C
(20 wt% Pt) sample were co-evaluated as well (see Support-
ing Information, Figures S8 and S9). Cyclic voltammograms
(CVs) of those catalysts were recorded using N2-saturated
0.1 M HClO4 solution at a scan rate of 50 mVsÀ1 (Figure S10)
and their CO-stripping tests were conducted in N2-saturated
0.1 M HClO4 solution between À0.2 and 0.9 V (vs. Ag/AgCl)
at a sweep rate of 50 mVsÀ1. The electrochemical surface
areas (ECSAs) were integrated using the region between 0.4
and 0.8 V (vs. Ag/AgCl), depicted in Figure S11 and Table S3.
As illustrated in Figure S11, the onset potential of CO electro-
oxidation peaks on CuNi@Pt-Cu nano-octahedra/C is over
30 mV more negative than that on the commercial Pt/C and
ꢀ 5 mV negative than that on the CuNi@Pt-Cu nano-poly-
hedra/C, indicating a weaker CO adsorption affinity on the
active sites of CuNi@Pt-Cu nano-octahedron surfaces and
higher electrochemical oxidation activity. Moreover, Table S3
summarizes the QCO/2QH ratios, where CuNi@Pt-Cu nano-
octahedra/C (1.13) and CuNi@Pt-Cu nano-polyhedra/C
(1.29) are higher than that of the commercial Pt/C (1.03),
implying the presence of the non-Pt element (Cu, in this
work) on the outer surfaces of the core@shell catalysts. This
result is consistent with the EDX elemental mapping analysis
discussed above.
The catalytic activity of the CuNi@Pt-Cu nano-octahedra/
C, as well as the counterparts towards MOR, was subse-
quently investigated. CV profiles of CuNi@Pt-Cu nano-
octahedra/C in N2-saturated solution containing 0.1 M
HClO4 + 1 M methanol are shown in Figure 3a and b. For
comparison, results from CuNi@Pt-Cu nano-polyhedra/C and
commercial Pt/C samples are also included. Figure 3a is based
on the specific activities that were calculated using the ECSA
determined from the CO-stripping experiments, whereas
Figure 3b is based on the mass activities that were calculated
from the loaded Pt mass on the electrodes. The electrode
potentials are reported versus an Ag/AgCl electrode. The
CVs show that the highest MOR current density was
determined from CuNi@Pt-Cu nano-octahedra/C. For exam-
ple, the maximum peak value of MOR current density on
À1
CuNi@Pt-Cu octahedra/C is 7.49 mAcmÀ2 (or 0.99 Amg ),
Pt
Figure 3. a,b) CV curves by normalizing with (a) specific area and (b) Pt loading mass of the three nano-catalysts (CuNi@Pt-Cu nano-octahedra/
C, CuNi@Pt-Cu nano-polyhedra/C, and commercial Pt/C) in N2-saturated 0.1 M HClO4 + 1 M methanol solution at a sweep rate of 50 mVsÀ1
c) Chronoamperometry (CA) curves of the three nano-catalysts at 0.75 V vs. Ag/AgCl measured in N2-saturated 0.1 M HClO4 + 1 M methanol
solution. d) Specific activities and mass activities of the three nano-catalysts at 0.75 V vs. Ag/AgCl.
.
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whereas those for the CuNi@Pt-Cu nano-polyhedra/C and
sess numerous structural features, such as {111} shape effect
and strain effect, and exhibit superior catalytic activity
À1
commercial Pt/C sample are 5.57 mAcmÀ2 (or 0.66 Amg
)
Pt
À1
and 1.30 mAcmÀ2 (or 0.23 Amg ), respectively. This indi-
towards MOR electrochemically. In the first report dissemi-
nated in this journal twelve years ago,[5] we ever demonstrated
that PtCu nanocubes terminated with {100} facets showed
outstanding MOR electrocatalytic activity (current density of
peak value: ꢀ 4.7 mAcmÀ2). Our current results indicate that
the {111}-profiled Pt-Cu facets originated from these core@-
shell nano-architectures can further promote the MOR
activity (current density of peak value: ꢀ 7.5 mAcmÀ2)
while the use of the Pt component is greatly reduced. This
work paves the way for integrating the three strategies of Pt-
based electrocatalyst improvement, that is, alloying with a 3d
metal, crystal shape control, and core@shell structure (with
lattice strain), into one design. Since most of the electro-
chemical reactions are catalyst facet- and surface composi-
tion-dependent, we envisage that the CuNi@Pt-Cu nano-
catalysts yielded from this approach could potentially possess
high activity towards other small molecule oxidation reac-
tions such as formic acid oxidation.
Pt
cates that MOR specific activity of core@shell CuNi@Pt-Cu
nano-octahedra/C is ꢀ 1.34- and ꢀ 5.76-fold higher than those
of CuNi@Pt-Cu nano-polyhedra/C and the commercial Pt/C
(or ꢀ1.50- and ꢀ 4.30-fold higher in mass activity), respec-
tively. A recent report[18] of hollow PtCu nano-octahedra
supports that the {111}-terminated facets of octahedral Pt-Cu
shell should add an advantage towards MOR in addition to
lattice strain effect. It is consequently believed that the lattice
strain and shape effect mainly contribute to the MOR activity
enhancement in CuNi@Pt-Cu nano-octahedra/C. As a coun-
terpart, the CuNi@Pt-Cu nano-polyhedra/C lacks {111} shape
effect and therefore exhibits lower MOR activity than
CuNi@Pt-Cu nano-octahedra/C (Table S4) although the
strain effect may still exist as confirmed in Table S2 and
Figure S8. The higher methanol oxidation current density on
CuNi@Pt-Cu nano-octahedra/C was further confirmed by the
chronoamperometric measurements performed at 0.75 V (vs.
Ag/AgCl) as shown in Figure 3c. CuNi@Pt-Cu nano-octahe-
dra/C exhibit the highest current density while on the contrary
CuNi@Pt-Cu nano-polyhedra/C and the commercial Pt/C are
either relatively decayed rapidly or remain low value. There-
fore, the developed core@shell CuNi@Pt-Cu nano-octahedra/
C facilitate the synergistic enhancement in MOR activity by
increasing the superior CO tolerance, which can also be
supported by the lower onset potential of CO-stripping peaks
(Figure S11). Figure 3d summarizes the MOR peak values of
the three typical catalysts presented in Figure 3a and b,
demonstrating that the CuNi@Pt-Cu nano-octahedra/C out-
perform the counterparts in terms of the MOR performance.
After the CA durability test, the CV profiles of CuNi@Pt-Cu
nano-octahedra/C and CuNi@Pt-Cu nano-polyhedra/C in N2-
saturated HClO4 solution were further recorded and are
presented in Figure S12. In CuNi@Pt-Cu nano-octahedra/C,
the negligible change in the HUPD area before and after the
CA durability test exhibits the high catalytic stability and
demonstrates that the compressive strain could downshift the
d-band center, weaken all the poisoning species binding
strength, and facilitate the MOR activity.[19] Although the
compressive strain also exists in the CuNi@Pt-Cu nano-
polyhedra/C, their HUPD area decreased after the CA
durability test, indicating that some of the Pt sites were
poisoned by the poisoning species. This further revealed that
the poisoning species have weakened the binding strength on
(111) facets rather than other facets, which is one of the main
reasons why the CuNi@Pt-Cu nano-octahedra/C show better
MOR performance than CuNi@Pt-Cu nano-polyhedra/C.
In conclusion, by taking advantage of the CuNi nano-
octahedron preparation achieved previously, we have suc-
cessfully demonstrated the preparation of octahedral
CuNi@Pt-Cu core@shell nanocatalysts. The shell formation
could be facilitated by a precise selection and tuning of the
experimental conditions, including the temperature
( ꢀ 1808C), heating rate ( ꢀ 28CminÀ1), the Pt precursor/
capping ligand (PtCl4), and other parameters. The thickness
of the Pt-based shell could be controlled to less than 1 nm.
The obtained CuNi@Pt-Cu core@shell nano-octahedra pos-
Acknowledgements
This work is primarily supported by the National Science
Foundation (DMR 1808383). We also acknowledge the
Center for Alkaline-Based Energy Solutions (CABES), an
Energy Frontier Research Center program supported by the
US Department of Energy, under Grant DE-SC0019445 for
its support of the CO-stripping measurements, as well as
partial support to C.L., X.C. and G.Z. thank the support by
the U.S. Department of Energy, Office of Basic Energy
Sciences, Division of Materials Sciences and Engineering
under Award No. DE-SC0001135 for TEM/EDX work. L.Z.
acknowledges the use of TEM facilities in the early stage for
the structural characterizations, at the Center for Functional
Nanomaterials, Brookhaven National Laboratory, which is
supported by the U.S. DOE, Office of Basic Energy Sciences
under Contract No. DE-SC0012704. Partial TEM imaging
work (low resolution) is supported by S3IP, State University
of New York at Binghamton. C.L. appreciates Yiliang Luan
for his help in the TEM characterization and useful sugges-
tions in the synthesis work and MOR characterization. C.L. is
also grateful to Dr. In-tae Bae for his training and support in
using the TEM facility.
Conflict of interest
The authors declare no conflict of interest.
Keywords: core@shell · CuNi@Pt-Cu · MOR activity ·
nanocatalysts · nano-octahedra
[1] a) E. D. Wachsman, K. T. Lee, Science 2011, 334, 935 – 939;
b) V. R. Stamenkovic, D. Strmcnik, P. P. Lopes, N. M. Markovic,
Nat. Mater. 2017, 16, 57 – 69; c) Z. W. Seh, J. Kibsgaard, C. F.
Dickens, I. Chorkendorff, J. K. Nørskov, T. F. Jaramillo, Science
2017, 355, eaad4998.
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Chemie
[2] H. A. Gasteiger, S. S. Kocha, B. Sompalli, F. T. Wagner, Appl.
Catal. B 2005, 56, 9 – 35.
2210; g) F. Kong, Z. Ren, M. Norouzi Banis, L. Du, X. Zhou, G.
Chen, L. Zhang, J. Li, S. Wang, M. Li, K. Doyle-Davis, Y. Ma, R.
Li, A. Young, L. Yang, M. Markiewicz, Y. Tong, G. Yin, C. Du, J.
Luo, X. Sun, ACS Catal. 2020, 10, 4205 – 4214.
[3] a) K. D. Gilroy, A. Ruditskiy, H.-C. Peng, D. Qin, Y. Xia, Chem.
Rev. 2016, 116, 10414 – 10472; b) M. Shao, Q. Chang, J.-P.
Dodelet, R. Chenitz, Chem. Rev. 2016, 116, 3594 – 3657; c) W.
Xiao, W. Lei, M. Gong, H. L. Xin, D. Wang, ACS Catal. 2018, 8,
3237 – 3256.
[8] X. Zhao, S. Chen, Z. Fang, J. Ding, W. Sang, Y. Wang, J. Zhao, Z.
Peng, J. Zeng, J. Am. Chem. Soc. 2015, 137, 2804 – 2807.
[9] a) S. Xie, S.-I. Choi, N. Lu, L. T. Roling, J. A. Herron, L. Zhang,
J. Park, J. Wang, M. J. Kim, Z. Xie, M. Mavrikakis, Y. Xia, Nano
Lett. 2014, 14, 3570 – 3576; b) J. Park, L. Zhang, S.-I. Choi, L. T.
Roling, N. Lu, J. A. Herron, S. Xie, J. Wang, M. J. Kim, M.
Mavrikakis, Y. Xia, ACS Nano 2015, 9, 2635 – 2647; c) Y. Xia,
K. D. Gilroy, H.-C. Peng, X. Xia, Angew. Chem. Int. Ed. 2017, 56,
60 – 95; Angew. Chem. 2017, 129, 60 – 98.
[10] a) M. Wang, L. Wang, H. Li, W. Du, M. U. Khan, S. Zhao, C. Ma,
Z. Li, J. Zeng, J. Am. Chem. Soc. 2015, 137, 14027 – 14030; b) C.
Li, Y. Luan, B. Zhao, A. Kumbhar, J. Fang, MRS Adv. 2019, 4,
263 – 269; c) C. Li, Y. Luan, B. Zhao, A. Kumbhar, X. Chen, D.
Collins, G. Zhou, J. Fang, MRS Adv. 2020, 5, 1491 – 1496.
[11] a) Z. Quan, H. Xu, C. Wang, X. Wen, Y. Wang, J. Zhu, R. Li, C. J.
Sheehan, Z. Wang, D.-M. Smilgies, Z. Luo, J. Fang, J. Am. Chem.
Soc. 2014, 136, 1352 – 1359; b) J. Zhang, J. Zhu, R. Li, J. Fang, Z.
Wang, Nano Lett. 2017, 17, 362 – 367; c) J. Zhang, Z. Luo, B.
Martens, Z. Quan, A. Kumbhar, N. Porter, Y. Wang, D.-M.
Smilgies, J. Fang, J. Am. Chem. Soc. 2012, 134, 14043 – 14049.
[12] H.-P. Liang, H.-M. Zhang, J.-S. Hu, Y.-G. Guo, L.-J. Wan, C.-L.
Bai, Angew. Chem. Int. Ed. 2004, 43, 1540 – 1543; Angew. Chem.
2004, 116, 1566 – 1569.
[4] a) J. Wu, P. Li, Y.-T. Pan, S. Warren, X. Yin, H. Yang, Chem. Soc.
Rev. 2012, 41, 8066 – 8074; b) S. Zhang, Y. Hao, D. Su, V. V. T.
Doan-Nguyen, Y. Wu, J. Li, S. Sun, C. B. Murray, J. Am. Chem.
Soc. 2014, 136, 15921 – 15924; c) H. Mistry, A. S. Varela, S. Kꢀhl,
P. Strasser, B. R. Cuenya, Nat. Rev. Mater. 2016, 1, 16009; d) M.
Luo, S. Guo, Nat. Rev. Mater. 2017, 2, 17059; e) Y. Xiong, Y.
Yang, F. J. DiSalvo, H. D. AbruÇa, J. Am. Chem. Soc. 2018, 140,
7248 – 7255; f) Q. Feng, S. Zhao, D. He, S. Tian, L. Gu, X. Wen,
C. Chen, Q. Peng, D. Wang, Y. Li, J. Am. Chem. Soc. 2018, 140,
2773 – 2776; g) X. Tian, X. Zhao, Y.-Q. Su, L. Wang, H. Wang, D.
Dang, B. Chi, H. Liu, E. J. M. Hensen, X. W. Lou, B. Y. Xia,
Science 2019, 366, 850 – 856; h) Z. Xia, S. Guo, Chem. Soc. Rev.
2019, 48, 3265 – 3278; i) Y. Qin, W. Zhang, K. Guo, X. Liu, J. Liu,
X. Liang, X. Wang, D. Gao, L. Gan, Y. Zhu, Z. Zhang, W. Hu,
Adv. Funct. Mater. 2020, 30, 1910107.
[5] a) D. Xu, Z. Liu, H. Yang, Q. Liu, J. Zhang, J. Fang, S. Zou, K.
Sun, Angew. Chem. Int. Ed. 2009, 48, 4217 – 4221; Angew. Chem.
2009, 121, 4281 – 4285; b) J. Zhang, H. Yang, J. Fang, S. Zou,
Nano Lett. 2010, 10, 638 – 644; c) J. Li, S. Sharma, X. Liu, Y.-T.
Pan, J. S. Spendelow, M. Chi, Y. Jia, P. Zhang, D. A. Cullen, Z.
Xi, H. Lin, Z. Yin, B. Shen, M. Muzzio, C. Yu, Y. S. Kim, A. A.
Peterson, K. L. More, H. Zhu, S. Sun, Joule 2019, 3, 124 – 135;
d) J. Li, Z. Xi, Y.-T. Pan, J. S. Spendelow, P. N. Duchesne, D. Su,
Q. Li, C. Yu, Z. Yin, B. Shen, Y. S. Kim, P. Zhang, S. Sun, J. Am.
Chem. Soc. 2018, 140, 2926 – 2932.
[6] a) J. Zhang, J. Fang, J. Am. Chem. Soc. 2009, 131, 18543 – 18547;
b) N. S. Porter, H. Wu, Z. Quan, J. Fang, Acc. Chem. Res. 2013,
46, 1867 – 1877; c) Y. Xia, X. Xia, H.-C. Peng, J. Am. Chem. Soc.
2015, 137, 7947 – 7966; d) Z. Zhao, H. Liu, W. Gao, W. Xue, Z.
Liu, J. Huang, X. Pan, Y. Huang, J. Am. Chem. Soc. 2018, 140,
9046 – 9050.
[7] a) P. Strasser, S. Koh, T. Anniyev, J. Greeley, K. More, C. Yu, Z.
Liu, S. Kaya, D. Nordlund, H. Ogasawara, M. F. Toney, A.
Nilsson, Nat. Chem. 2010, 2, 454 – 460; b) C. Chen, Y. Kang, Z.
Huo, Z. Zhu, W. Huang, H. L. Xin, J. D. Snyder, D. Li, J. A.
Herron, M. Mavrikakis, Science 2014, 343, 1339 – 1343; c) L.
Zhang, L. T. Roling, X. Wang, M. Vara, M. Chi, J. Liu, S.-I. Choi,
J. Park, J. A. Herron, Z. Xie, M. Mavrikakis, Y. Xia, Science
2015, 349, 412 – 416; d) X. Wang, S.-I. Choi, L. T. Roling, M. Luo,
C. Ma, L. Zhang, M. Chi, J. Liu, Z. Xie, J. A. Herron, M.
Mavrikakis, Y. Xia, Nat. Commun. 2015, 6, 7594; e) C. Wang, X.
Sang, J. T. L. Gamler, D. P. Chen, R. R. Unocic, S. E. Skrabalak,
Nano Lett. 2017, 17, 5526 – 5532; f) C. Wang, L. Zhang, H. Yang,
J. Pan, J. Liu, C. Dotse, Y. Luan, R. Gao, C. Lin, J. Zhang, J. P.
Kilcrease, X. Wen, S. Zou, J. Fang, Nano Lett. 2017, 17, 2204 –
[13] F. Tao, M. E. Grass, Y. Zhang, D. R. Butcher, J. R. Renzas, Z.
Liu, J. Y. Chung, B. S. Mun, M. Salmeron, G. A. Somorjai,
Science 2008, 322, 932 – 934.
[14] JCPDS ICDD 48-1549.
[15] a) F. Zhao, Q. Yuan, B. Luo, C. Li, F. Yang, X. Yang, Z. Zhou,
Sci. China Mater. 2019, 62, 1877 – 1887; b) J. Zhang, H. Yang, B.
Martens, Z. Luo, D. Xu, Y. Wang, S. Zou, J. Fang, Chem. Sci.
2012, 3, 3302 – 3306.
[16] a) C. Wang, D. van der Vliet, K. L. More, N. J. Zaluzec, S. Peng,
S. Sun, H. Daimon, G. Wang, J. Greeley, J. Pearson, A. P.
Paulikas, G. Karapetrov, D. Strmcnik, N. M. Markovic, V. R.
Stamenkovic, Nano Lett. 2011, 11, 919 – 926; b) J. Yang, J. Yang,
J. Y. Ying, ACS Nano 2012, 6, 9373 – 9382.
[17] Z. Wang, G. Yang, Z. Zhang, M. Jin, Y. Yin, ACS Nano 2016, 10,
4559 – 4564.
[18] G. Chen, X. Yang, Z. Xie, F. Zhao, Z. Zhou, Q. Yuan, J. Colloid
Interface Sci. 2020, 562, 244 – 251.
[19] J.-H. Choi, K.-W. Park, I.-S. Park, K. Kim, J.-S. Lee, Y.-E. Sung, J.
Electrochem. Soc. 2006, 153, A1812 – A1817.
Manuscript received: October 21, 2020
Revised manuscript received: January 5, 2021
Accepted manuscript online: January 13, 2021
Version of record online: February 25, 2021
7680 www.angewandte.org
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