Hexapod PtRuCu Nanocrystalline Alloy for Highly Efficient and Stable Methanol Oxidation

Article abstract of DOI:10.1021/acscatal.8b00366

A hexapod PtRuCu nanocrystalline alloy material is successfully fabricated by a facile approach based on Stranski-Krastanov growth and galvanic replacement and used as an efficient catalyst for direct methanol fuel cells (DFMCs). Because of the synergetic effect of metallic elements in the methanol oxidation, the activity and durability of the prepared PtRuCu/C catalyst is significantly enhanced. It has a mass activity of 1.35 A mg_Pt^-1 and a specific activity of 3.92 mA cm^-2, which are 3.8 and 8.2 times higher than those of Pt/C, respectively. Its mass activity only decreases 27% after 800 CV cycles compared with Pt/C (60% decline), indicating the admirable stability of the PtRuCu catalyst.

Full text of DOI:10.1021/acscatal.8b00366

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Article
Hexapod PtRuCu Nanocrystalline Alloy for
Highly Efficient and Stable Methanol Oxidation
Shengfeng Xue, Wentao Deng, Fang Yang, Jinlong Yang,
Ibrahim Saana Amiinu, Daping He, Haolin Tang, and Shichun Mu
ACS Catal., Just Accepted Manuscript • Publication Date (Web): 09 Jul 2018
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Hexapod PtRuCu Nanocrystalline Alloy for Highly
Efficient and Stable Methanol Oxidation
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†
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Shengfeng Xue,1 Wentao Deng,2 Fang Yang,1 Jinlong Yang,1 Ibrahim Saana Amiinu,1 Daping He, 1,3
*
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Haolin Tang, 1* Shichun Mu1*
1
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan
University of Technology, Wuhan 430070, China
2 Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K.
3 Hubei Engineering Research Center of RFꢀMicrowave Technology and Application, Wuhan University
of Technology, Wuhan 430070, China
Eꢀmail: hedaping@whut.edu.cn, tanghaolin2005@yahoo.com.cn, msc@whut.edu.cn
KEYWORDS: Pt • ternary metallic alloy • methanol oxidation reaction (MOR) • hexapod •
electrochemical catalysis
ABSTRACT
A hexapod PtRuCu nanocrystalline alloy material is successfully fabricated by a facile approach based on
StranskiꢀKrastanov growth and galvanic replacement and used as an efficient catalyst for direct methanol
fuel cells (DFMCs). Due to a synergetic effect of metallic elements in the methanol oxidation, the activity
and durability of the prepared PtRuCu/C catalyst is significantly enhanced. It has a mass activity of 1.35
A mgPt and a specific activity of 3.92 mA cmꢀ2, which are 3.8 and 8.2 times higher than those of Pt/C,
ꢀ1
respectively. Its mass activity only decreases 27% after 800 CV cycles compared to Pt/C (60% decline),
indicating the admirable stability of the PtRuCu catalyst.
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INTRODUCTION
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Direct methanol fuel cells (DMFCs) are promising and efficient devices in the conversion of
chemical energy into electric power for portable communication devices and small vehicles due to the
high energy density.1 The application of catalysts has attracted enormous attention in order to increase the
efficiency of DMFCs, and of which Pt is found to be an ideal anode catalyst attributed to its distinct
electronic properties for methanol oxidation reaction (MOR).2ꢀ4 However, the active sites on pure Pt are
easily adsorbed and blocked by intermediate products, causing the retard of further reactions. This
poisoning phenomenon is particularly serious in an acidic electrolyte.4
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Researchers in recent years have worked on developing platinum alloys (PtM, M=Pd5, Ru6, Cu7, Co8,
Ni9 etc.) to avoid the catalyst poisoning, especially the poisoning problem caused by CO and HCOOH
which are produced at the active sites on Pt particles during the MOR reaction. An alloy catalyst could
reduce the CO poisoning depending on the properties of the additionally introduced metal element. For
example, it has been reported that catalysts based on PtRu alloys show impressive CO tolerance due to
the fact that CO can be easily oxidized by the aid of Ru(OHꢀ).10ꢀ11 Another catalyst, PtCu also has high
electrocatalytic performance as MOR catalyst, owing to the fact that Cu can lower the d band center of Pt,
which could protect Pt and its active sites from CO blocking.12ꢀ13
In addition, alloys with controlled morphologies, such as nanowires14, nanocages15, nanodendrites16,
nanoframes17, or coreꢀshell structures18 have been employed to minimize Pt loading and maximize the
stability and activity of catalysts, especially nanomaterials with distinct 3D structures possess better
catalytical activities in virtue of abundant active sites and large specific areas.19ꢀ20 Recently, diversified
reagents have been found conducive to synthesize nanoparticles with controlled morphologies or new
structures. For instance, CO can play a significant role in constructing Pt nanocubes and meanwhile
limiting the growth of PtCu nanoparticles.21 By the assistance of CO, nanomaterials with special
morphologies can be created22. Cetyltrimethyl Ammonium Bromide (CTAB) has also been reported to be
a surfactant propitious to form high index facets (HIFs) like Pt(110) or (111) which can improve the
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catalyst activity and affect reduction rates through ligand effects in metal nanoparticle fabrication.23ꢀ24
Despite the fact that many researchers have developed catalysts with high catalytic efficiency, most of
their synthetic methods are complicated.25ꢀ26
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In this work, we report a facile synthesis approach for making ternary PtRuCu alloy nanoparticles
with a hexapod structure. In a typical procedure, Cu(COOH)2 was reduced to produce Cu seeds colloidal
by the assistance of oleylamine, glucose and CTAB in the atmosphere of CO. Oleylamine containing
Pt(acac)2 and Ru(acac)3 were then added into the colloidal to get PtRuCu alloying nanocrystals (See
details in experimental section). The electrocatalytic performance of the asꢀsynthesized catalyst was
studied in acidic electrolyte containing methanol. The results indicated that the hexapod PtRuCu alloy
nanocrystals possessed greatly enhanced performance when used as a methanol oxidation catalyst
compared with the commercial Pt/C catalyst.
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EXPERIMENTAL SECTION
Chemicals and Materials
Platinum acetylacetonate (Pt(acac)2, 97.0%), ruthenium acetylacetonate (Ru(acac)3，97.0%), cupric
acetate (Cu(COOH)2, 97.0%), oleylamine (C18H37N, 80~90%) and cetyltrimethylꢀ ammonium bromide
(CTAB, 99%) were all purchased from Macklin, China. Glucose (AR), methanol (AR), absolute ethanol
(AR), toluene (AR) and isopropanol (AR) were all supplied by Aldrich. Vulcan XCꢀ72 was purchased
from SigmaꢀAldrich. Perchloric acid (HClO4, 70~72%) was purchased from Aladdin. Carbon monoxide
(CO, 99.5%) was purchased from Beiwen gas factory, China. Nafion solution (5 wt%) was purchased
from SigmaꢀAldrich. Commercial Pt/C for comparison was purchased from Johnson Matthey. All
chemicals were used directly without further purification.
Synthesis of PtRuCu alloy
To prepare the PtRuCu hexapods, Cu(COOH)2 (7.2 mg, 0.04 mmol), glucose (60 mg, 0.3 mmol), CTAB
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(73 mg, 0.2 mmol) were dissolved in oleylamine (5mL, 13 mmol), and sonicated for 30 minutes to get a
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homogeneous solution. After a removal of oxygen under vacuum, the solution was heated to 270℃ and
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kept at this temperature under carbon monoxide atmosphere for 30 minutes with vigorous stirring. Then,
it was cooled down to room temperature before 5 mL oleylamine solution containing Pt(acac)2 (20.4 mg,
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0.052 mmol) and Ru(acac)3 (3.2 mg, 0.008 mmol) were added. The solution was again heated up to 300℃
and kept for 1h with stirring. The products were collected by washing under centrifugation at 10000 rpm
with the mixture of toluene and methanol (v/v=1:1) for at least three times. PtCu alloy was synthesized by
the same method in the absence of Ru(acac)3. PtRuCu dendrites were synthesized by the same method
except changing the holding time at 300℃ from 1h to 2 h.
Materials Characterization
Morphologies of PtRuCu alloy were carried out by a transmission electron microscopy (TEM)
(JEMꢀ2100F STEM/EDS, JEOL, Japan) operated at 200 kV. Powder Xꢀray diffraction (XRD) was tested
on an Xꢀray diffractometer (D/MAXꢀRB, Rigaku, Japan) with a KαCu Xꢀray source (λ=1.530598Å). The
content of each element in the catalyst was determined by Inductive Coupled Plasma Optical Emission
Spectrometer (ICPꢀOES) (Prodigy 7, Teledyne Leeman Labs). Xꢀray photoelectron spectroscopy (XPS)
measurements were performed by ESCALAB 250Xi.
Electrochemical Measurements
The electrochemistry measurements were carried out by using a threeꢀelectrode system on an
electrochemical workstation (CHI 760E, Chenhua Co., Shanghai, China). A glassy carbon electrode (GCE,
5 mm diameter), a saturated calomel electrode (SCE) and a platinum wire were used as the working
electrode, the reference electrode and the counter electrode, respectively. The asꢀsynthesized PtRuCu
alloy was mixed with Vulcan XCꢀ72 (nanoparticle to carbon w/w=20/80) in a 10 mL ethanol aqueous
solution (90 vol%). The slurry was sonicated for an hour before centrifugation. The sediment was
collected and dried at 80℃ in a drying box for 12 hours to prepare the catalyst labeled as PtRuCu/C. 5
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mg PtRuCu/C was mixed with 1000 ꢁL isopropanol aqueous solution (90 vol%) and 20ꢁL Nafion
solution (5 wt%) to prepare the ink for electrochemistry measurements. 5 ꢁL ink was dropped on the
electrode for each measurement.
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Cyclic voltammogram (CV) measurements were carried out in a threeꢀelectrode system with 0.1 M
HClO4 as the electrolyte at a scan rate of 50mV sꢀ1, and the potential window is from ꢀ0.3V to 0.9V.
Before the measurements, the electrolyte was blown with nitrogen for 20 minutes.
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Methanol oxidation reaction (MOR) curves were also obtained in 1M methanol and 0.1 M HClO4 by
cyclic voltammogram in a threeꢀelectrode system as mentioned above. The system was scanned at 50mV
sꢀ1 in the potential range from 0 V to 1.2 V. Electrolyte used was bubbled with nitrogen before and during
the MOR measurements.
CO stripping curves were obtained in 0.1M HClO4. Before each measurement, CO was bubbled into the
electrolytic cell for 10 min. Then the potential of the working electrode was hold at 0.1V vs. reversible
hydrogen electrode (RHE) for 10 min via iꢀt technique to make CO adsorbed on the catalyst. After that,
CO was removed from the electrolyte by bubbling N2 for 30 min. Then CO stripping curves were
recorded at a scan rate of 50mV/s between 0.05 V and 1.2 V vs RHE.
RESULTS AND DISCUSSION
As shown in Figure. 1a, b and c, the hexapod PtRuCu nanocrystal particles with six identical arms
can be identified by transmission electron microscopy (TEM). They can be regarded as an octahedral
structure with six islands on each corner. More evidences can be found in the structure evolution observed
through TEM images (Figure. 2). In addition, the Fast Fourier Transform (FFT) pattern (Figure. 1d)
shows a regularly arranged spots, indicating that the PtRuCu hexapods is presented in a single crystal
with the (111) facets. As shown in Figure 1a, such particles have a size range of 26ꢀ30 nm based on TEM
observation, and the average size is about 28 nm. As shown in the high resolution TEM images (Figure.
1e), the spacing of the lattice fringes of PtRuCu nanoparticles is 0.22 nm, corresponding to PtCu (111)
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facet.27 Elemental mappings of the product manifested that Pt, Ru and Cu are uniformly distributed in the
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hexapod PtRuCu particles. (Figure. 1f-i)
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Figure 1 (a) TEM images of PtRuCu hexapods; (bꢀc) HRTEM image of PtRuCu hexapods viewed from
two perspectives and their corresponding models as insets; (d) FFT pattern of Figure (b); (e) magnified
selected area in Figure (b), (fꢀi) the corresponding elemental mappings of Pt, Ru and Cu.
The structure evolution from Cu particles to PtRuCu hexapods is illustrated in Figure 2. As described in
the experimental part, the reactions correspond to two stages. Copper particles were firstly obtained
through reduction of Cu(OAc)2 (Figure 2a). At the second stage which relates to the StranskiꢀKrastanov
growth and galvanic replacement,5 the reaction time was found of great importance in determining the
composition and morphology of the product. When the reaction system was kept for 30 min at 300 °C
after the addition of Pt(acac)2 and Ru(acac)3 (noting that the Pt and Ru precursors were added at the same
time), the resulted product was octahedral (Figure 2c) rather than the hexapods (Figure 2d). When
Pt(acac)2 and Ru(acac)3 were added into the reaction system, Pt(acac)2 was reduced to Pt, and PtCu
octahedra were then constructed.27ꢀ28 This process is prior to the reduction of Ru(acac)3 due to the more
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positive reduction potential of PtII. With the proceeding of the reaction, PtII and RuIII were both reduced
and then constructed a skin on PtCu octahedra based on a layerꢀbyꢀlayer mechanism (epitaxial growth).
However, the standard potential of PtII/Pt pair (1.18V) are more
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Figure 2 (a) Structure evolution from Cu particles to PtRuCu hexapods and (bꢀd) corresponding TEM
images for Cu particles, PtCu octahedra and PtRuCu hexapods.
positive than that of CuII/Cu pair (0.34V), giving rise to a galvanic replacement between PtII and Cu, and
it then results in the presence of Pt and Ru atoms in the core of the hexapods according to the elemental
maps of PtRuCu hexapods.29 When the reaction time was sufficient (i.e. 60 min in this work), Cu
(reduced from CuII being replaced in the presence of Pt atoms) Pt and Ru started preferential growth at six
vertices of the octahedra and formed PtRuCu hexapods with octahedra cores. Simultaneously, the
galvanic replacement was still continuing, which was the main reason that the distribution of Pt was
basically the same as that of Cu in elemental maps. However, when the reaction time was extended to 2 h,
the PtRuCu hexapods would grow into crystals with more complex morphologies like dendrites (Figure
S1).
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The alloy was further investigated by powder Xꢀray diffraction (XRD) measurement to understand
the phase and crystal information. The obtained XRD patterns of Pt/C, PtCu/C, PtRu/C and PtRuCu/C are
shown in Figure 3a. It is observed that the peaks of PtRuCu shift to higher angles compared with pure Pt
(JCPDS: 04ꢀ0802), indicating that Pt has been alloyed with other metals. The XRD pattern of PtRuCu is
similar to that of PtCu, but slightly shifts toward the peaks of PtRu. The Peaks located at 41.4°, 48.1°
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and 70.6°can be assigned to (111), (200) and (220) facets of PtCu, respectively30. The XRD pattern of
PtRuCu dendrites were also measured and the dendrites show a similar crystal structure with PtRuCu
hexapods (Figure S2). Noting that no Ru phase was detected in XRD patterns in both PtRu and PtRuCu
due to the detection limit of XRD measurement. To prove the existence of Ru in the alloy, Energy
Figure 3 (a) XRD patterns of Pt/C, PtRu/C, PtCu/C and PtRuCu(hexapods)/C. PDF cards of Pt
(JCPDS:04ꢀ0802, black), Ru (JCPDS:06ꢀ0663, red) and Cu (JCPDS:48ꢀ1549, blue) are as illustrated
below the XRD patterns; (b)EDS spectrum of PtRuCu hexapods; (c)XPS spectra in Pt 4f region for
PtRuCu/C and commercial Pt/C.
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Dispersive Spectrometer (EDS) and TEM elemental mapping were employed and confirmed the existence
of Ru (Figure 1f and Figure 3b), and Ru accounts for 0.5 at% in the alloy, identified by ICPꢀOES. The
content of Pt and Cu was also measured to be 51.5 at% and 48 at%. As shown in Figure 3c, the XPS
spectrum of Pt in 4f regions can be decomposed into two groups of peaks: Pt (0) (71.18 eV and 74.58 eV)
and Pt (II) (72.98 eV and 76.38 eV, listed in Table S1). Significantly, the Pt (0) peak of PtRuCu/C located
at 71.18 eV (4f 5/2) shows a 0.32 eV negative shift in comparison with the commercial Pt/C (71.50 eV).
In the Cu 2p spectrum, peaks located at 952.66 eV (Cu 2p 1/2) and 932.80 eV (Cu 2p 3/2) indicate the
presence of Cu (Figure S3), and the positive shifts of Cu 2p peaks compared with metallic Cu indicate
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the decline of Cu electron density and a downshift of the dꢀband center of Pt, which is beneficial for the
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catalytic activity.
Both Ru 3d and Ru 3p peaks are shown in Figure S4. It is difficult to distinguish
the peaks of Ru 3d peak and C1s (Figure S4a), as Ru 3d peak is close to C 1s peak and the content of Ru
is rather low (0.5%). However, Ru can be observed via XPS spectra in the Ru 3p region, which is shown
in Figure S4b. An evolution of composition change has been illustrated by XPS spectra (Figure S5) in
which the element and content information from Cu particles, PtCu octahedra to PtRuCu hexapods are
exhibited.
To compare the electrocatalytic performances of asꢀsynthesized catalyst to the commercial Pt/C,
cyclic voltammetry(CV) and methanol electrooxidation experiments were conducted. From the CV
curves in Figure 4a, the electrochemical active surface area (ECSA) of the three catalysts were
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determined to be 34.57 m2/gPt (PtRuCu hexapods/C), 52.28 m2/gPt (PtRuCu dendrites/C), 13.3
m2/gPtꢀ1(PtCu/C) and 74.62 m2/gPtꢀ1(Pt/C). Compared with commercial Pt/C, the decreased ECSA of
PtRuCu/C can be ascribed to the large sizes of metallic nanoparticles.20
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Figure 4 Electrocatalytic activity and stability performances of PtRuCu hexapods/C (PtRuCu/C), PtRuCu
dendrites/C, PtCu/C and commercial Pt/C. (a) CV curves in 0.1M HClO4; (b) Mass activity in 0.1M
HClO4 + 1M CH3OH solution for commercial Pt/C, PtRuCu hexapods/C (PtRuCu/C), PtRuCu
dendrites/C and PtCu/C, respectively; (c) MOR mass activity and specific activity in 0.1M HClO4 + 1M
CH3OH solution for commercial Pt/C, PtRuCu hexapods/C (PtRuCu/C), PtRuCu dendrites/C and PtCu/C;
(d)MOR durability comparison of commercial Pt/C and PtRuCu hexapods/C (PtRuCu/C).
The prepared PtRuCu trimetallic catalyst shows impressive electrocatalytic performance. When used
for methanol oxidation reaction (MOR), as displayed in Figure 4b, the PtRuCu/C catalyst owns nearly a
threeꢀfold mass activity (1.35A mg Ptꢀ1) over the commercial Pt/C catalyst (0.47A mgPtꢀ1). Moreover, as
shown in Figure 4c, it exhibits a higher specific activity than the commercial Pt/C (5.22 vs. 0.59 mA cmꢀ2)
and a better activity than the PtRuCu dendrites/C catalyst (1.35 A mg ꢀ1 vs 1.13 A mg ꢀ1). The activity
Pt
Pt
difference is partly caused by the different morphologies between them. As the PtRuCu hexapods were
not completely grown, therefore, some high index facets (such as Pt (111) on PtCu octahedra) on the alloy
were still exposed. This helps to enhance the catalysis activity. As another important index, the ratio of If
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(forward current) to Ib (backward current) can be used to estimate the tolerance of the catalyst to the
poisoning of intermediate carbonaceous species such as CO, HCHO and HCOOH.27 The ratio calculated
from Figure 4b indicates that PtRuCu/C (If/Ib=1.32) has better durability (antiꢀCO poisoning capability)
than commercial Pt/C (If/Ib=0.84). In addition, after hundreds of CV cycles, PtRuCu/C and commercial
Pt/C catalyst display relatively different stability behaviors (Figure S6). The activity of PtRuCu/C
degraded in a much slower rate after the first 200 CV cycles than the commercial Pt/C, and eventually its
activity only decreased 27% after 800 CV cycles, which is much better than that of Pt/C (60% decreased,
as exhibited in Figure 4d and Figure S6). Interestingly, after 800 CV cycles, the PtRuCu dendrites/C also
shows high stability with only 18% decays for MOR catalytic activity (Figure S6c). Notably, PtRuCu /C
maintains higher If/Ib ratio compared with commercial Pt/C (1.27 vs 1.10) at the 800th CV scan,
suggesting that PtRuCu is still tolerant to CO poisoning even after hundreds of CV cycles (Figure S7).
We further investigated the CO tolerance of PtRuCu/C, PtRu/C and Pt/C catalysts by CO stripping
test in 0.1M HClO4 at a scan rate of 50 mV/s. The CO stripping curves are shown in Figure 5. The CO
stripping peak of PtRuCu/C (0.85 V) locates at a lower potential than that of Pt/C (0.91 V), indicating a
higher CO tolerance of PtRuCu/C catalyst than that of Pt/C. The commercial PtRu/C catalyst shows the
lowest peak potential (0.61 V), due to the higher Ru content (~20 wt.%).
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Figure 5 CO stripping curves of commercial Pt/C, commercial PtRu/C and PtRuCu hexapods/C in 0.1 M
3
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HClO4.
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The good MOR activity and stability of PtRuCu hexapods can be attributed to the synergetic effects
of the three metallic elements in the alloy. As a single element catalyst, Pt suffers from poisoning problem.
However, introducing other elements to produce Ptꢀcontaining alloy can significantly reduce the impacts
of poisoning. It has been reported that the formation of Ru(OHꢀ) in the reaction catalyzed by PtRu alloy
can improve the stability of the catalyst. The Ruꢀbased catalyst is excellent for methanol oxidation
resulting from following reactions:33
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Pt+CH3OH →Pt(CO)ads +4H+ +4eꢀ
Ru+H2O →Ru(OHꢀ )ads +H+ +4eꢀ
(1)
(2)
Pt(CO)ads +Ru(OHꢀ )ads →CO2 +Pt+Ru+H+ +eꢀ (3)
This mechanism indicates that the existence of Ru, which is prone to form Ru(OH)ads, can conduce the
oxidation of CO. Therefore, CO poisoning of active sites on Pt can be reduced. It is also discovered that
the onset potential of PtRuCu/C is 0.22V, lower than that of commercial Pt/C (0.31V), which manifests
that CO can be removed from active sites on Pt at a lower potential after being oxidized by Ru(OHꢀ)
(Figure 4b).26
In addition to Ru, introducing of Cu into the alloy is also beneficial to the antiꢀpoisoning capability.
When alloyed with Cu, Pt can achieve a modified dꢀband by a ligand and strain effect to maintain a
constant dꢀband filling, thereby electron structures and chemical properties can be changed on the surface
of the alloy.34ꢀ36 Subsurface 3d transition metal atoms improve the broadening of dꢀband on the Pt surface
by the interactions between Pt atoms and Cu atoms, thus the average dꢀband energy can be decreased.
This is conducive to the desorption of CO produced in the methanol oxidation reaction at the active sites
on Pt, thereby the durability of the catalyst can be enhanced.12, 37 Furthermore, Cu atoms on the surface of
PtRuCu alloy can be sacrificed to relieve Pt from dissolution, thus the activity and durability of PtRuCu/C
can be improved in acidic electrolytes. The combination of the fact that Ru(OH)ads can relieve Pt from
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poisoned by CO and the synergetic effect between Pt and Cu is believed to be the major contribution of
enhanced MOR activity of the catalyst.
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CONCLUSIONS
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In summary, by using a facile method, we synthesized a PtRuCu alloy with a hexapod structure for
robust methanol oxidation catalytic performance. The ternary alloy hexapods were formed by the
combination of StranskiꢀKrastanov growth and galvanic replacement. For the methanol oxidation reaction
(MOR), the fabricated PtRuCu/C catalyst exhibits 3.8ꢀfold mass activity, 8.2ꢀfold specific activity and
increased durability compared with the commercial Pt/C catalyst. The reaction time is a crucial factor to
obtain alloy with wellꢀdefined morphology and robust activity. This promising catalyst is attributed to the
synergetic effect of Pt, Ru and Cu components. Ru(OH)ads formed in the reactions speeds up the oxidation
of CO, and Cu doping could decorate the dꢀband and decrease the dꢀband energy of Pt. Therefore, the
activity and stability of the Ptꢀbased catalyst are both enhanced.
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ASSOCIATED CONTENT
Supporting Information
The supporting information is available free of charge on the ACS Publication website.
TEM images and XRD patterns of PtRuCu dendrites; XPS spectra of PtRuCu, PtCu and Cu; and MOR
performances after different CV cycles of Pt/C, PtRuCu/C and PtRuCu dendrites/C; Catalyst durability of
commercial Pt/C and PtRuCu/C; and the reaction devices used in the synthesis. (PDF)
AUTHOR INFORMATION
Corresponding Author
Eꢀmail: hedaping@whut.edu.cn, tanghaolin2005@yahoo.com.cn, msc@whut.edu.cn
Author Contributions
†S.X., W.D., and F.W. contributed equally to this work.
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Conflicts of interest
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The authors declare no competing financial interest
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ACKNOWLEDGMENT
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This work was supported by the National Natural Science Foundation of China (51672204, 51701146).
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