In situ formation of N- and Fe-doped carbon nanotube/mesoporous carbon nanocomposite with excellent activity for oxygen reduction in acidic media

Article abstract of DOI:10.1039/c5ra15487a

An N- and Fe-doped carbon nanotube/CMK3 nanocomposite (NFe-CNT/CMK3) was firstly prepared by a simple procedure. Trace Fe³⁺ can catalyze the in situ growth of the N- and Fe-doped carbon nanotube from melamine as a CNT precursor. The typical product shows excellent catalytic ability for the oxygen reduction reaction (ORR) in acidic media. The value of the onset potential and half-peak potential of the typical product is only 68.0 mV and 63.0 mV less than that of the commercial 20% Pt/C catalyst, respectively. The product also reveals superior stability and tolerance to methanol poisoning effects compared to Pt/C. We believe that the NFe-CNT and NFe-CMK3 in the nanocomposite have synergistically enhanced electrochemical activities for ORR in acidic media. The proposed method is simple and readily scalable. We anticipate such a nanoporous nanocomposite will have broad applications in other fields such as supercapacitors, lithium ion batteries, gas uptake, biosensors, removal of pollutants and so on.

Full text of DOI:10.1039/c5ra15487a

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N- and Fe-doped Carbon Nanotube/CMK3 Nanocomposite was firstly prepared by a
simple procedure. The typical product shows excellent catalytic ability for
oxygen reduction reaction in the acidic media.

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In Situ Formation of N- and Fe-doped Carbon Nanotube/
Mesoporous Carbon Nanocomposite with Excellent Activity for
Oxygen Reduction in Acidic Media
a
a
a
b, *
a
XiangꢀJun Huang , YaꢀNan Luan , PengꢀFei Yao , JinꢀSong Xie , Liang Yu ,
a
a,*
ZhenꢀYu Wu , Ping Chen
a School of Chemistry and Chemical Engineering, Anhui University, Hefei, Anhui,
30601, P. R. China
b Department of Chemistry and Materials Engineering, Hefei University, Hefei，Anhui,
2
230601,P.R.China
*
Correspondence to: Dr. P. Chen (Eꢀmail: chenping@ahu.edu.cn); Dr. J. S. Xie
(Eꢀmail: xjs153@hfuu.edu.cn)
†
Electronic supplementary information (ESI) available
Abstract
Nꢀ and Feꢀdoped Carbon Nanotube/CMK3 Nanocomposite (NFeꢀCNT/CMK3) was
3+
firstly prepared by a simple procedure. Trace Fe can catalyze the in situ growth of the
Nꢀ and Feꢀdoped Carbon Nanotube from the melamine as CNT precursor. The typical
product shows excellent catalytic ability for oxygen reduction reaction (ORR) in the
acidic media. The value of onset potential and halfꢀpeak potential of the typical product
is only 68.0 mV and 63.0 mV less than that of the commercial 20 % Pt/C catalyst,
respectively. The product also reveals superior stability and tolerance to methanol
poisoning effects compared to the Pt/C. We believe that the NFeꢀCNT and NFeꢀCMK3
1

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in the nanocomposite have the synergistically enhanced electrochemical activities for
ORR in acidic media. The proposed method is simple and readily scalable. We
anticipate such a nanoporous nanocomposite will have broad applications in the other
fields such as supercapacitors, lithium ion batteries, gas uptake, biosensors, removal of
pollutant and so on.
Introduction
In view of the increasingly serious energy crisis and the challenge of the greenhouse
effect, fuel cell is one of the most promising to alternative energy sources because it has
1
,2
high power density and no any pollution. Electrocatalysts for the oxygen reduction
reaction (ORR) are crucial in fuel cells. Because of the scarcity of platinum, developing
nonꢀprecious metal or metalꢀfree electrocatalysts for ORR with high activity has been
3
ꢀ6
regarded as an important issue. In the past several years, many highꢀperformance
7
ꢀ12
ORR catalysts in the alkaline media have been developed. However, it is wellꢀknown
that proton exchange membrane (PEM) fuel cells can only be worked with acidic
electrolytes. Unfortunately, the catalysts exhibit the dissatisfactory or even very weak
6
,13ꢀ15
ORR performance in acidic media.
The another important issue is, for the purpose
of the practical application in the fuel cells, the ORR catalysts should be lowꢀcost and
highꢀvolume production. Therefore, developing highꢀperformance nonꢀprecious metal
ORR electrocatalysts in acidic media with cheap and commercially available materials
5
,16,17
is a great challenge in the practical application of fuel cell.
Recently, Nꢀdoped carbon materials have been a promising metalꢀfree electrocatalysts
18
for ORR, because of a large number of active sites and high conductivity. Especially,
2

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the Nꢀdoped carbon catalysts such as carbon nanotubes, graphene and carbon
nanotubeꢀgraphene complexe have been developed and shown the ORR activity in
19
acidic media. The addition of certain transition metals to the nitrogenꢀdoped carbon
20,21
materials can improve the ORR activity in acidic media.
Fe and Co elements have
been added to the carbon materials to improve the ORR activity because these metal
cations can coordinate with the nitrogen doped in the carbon materials so as to increase
22
the active sites for ORR. However, in the design of these catalysts, careful selection of
2
2ꢀ25
suitable nitrogen/transitionꢀmetal precursors and carbon supports is very important.
Nitrogenꢀdoped carbon nanotubes have received increasing attention as ORR catalysts,
because of strong stability. In the past several years, some effective ORR catalysts
10,19,26
based on the carbon nanotubes have been developed.
In principle and fact, in order to improve the ORR activity, nanoscale porosity is highly
27,28
desirable, which can facilitate high mass transfer fluxes.
It is wellꢀknown that the
mesoporous carbon has the pore size ranging from 2 to 50 nm, so that it can be a
potential candidate electrocatalyst because of the high surface area and various pore
21,28ꢀ30
sizes
Very importantly, so far, great progress in the preparation of mesoporous
carbon material has been made. For example, CMKꢀ3 (an ordered mesoporous carbon)
can be manufactured on the large scale at lowꢀcost and has become the commercially
29,31
available materials.
1
0,17,31ꢀ34
Based on the above consideration and our recent study,
here, the Nꢀ and
Feꢀdoped carbon nanotube/CMK3 nanocomposite (NFeꢀCNT/CMK3) was firstly
prepared. We develop a facile and readily scalable approach to synthesize the lowꢀcost
3

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and excellent electrocatalyst for the ORR. The NFeꢀCNT and NFeꢀCMK3 in the
nanocomposite have the synergistically enhanced electrochemical activities for ORR in
acidic media.
Experimental methods
All reagents are of analytical reagent grade and used without further purification.
CMK3 was purchased from Nanjing XFNANO Materials Tech Co., Ltd. The
specific surface area, porosity and mean pore size of the CMK3 were provided in the
Fig. S1.
Preparation of N- and Fe-doped Carbon Nanotube/CMK3 Nanocomposite
(NFe-CNT/CMK3). Firstly, 60.0 mg CMK3 was dispersed in the 10 mL distilled water
to form the mixture. Then, 6.0 mg FeCl was added to the mixture, which was stirred
3
o
magnetically at 25 C for 50 min. The dried mixture was obtained by freeze drying for
12 h. Finally, the dried mixture and 500 mg melamine were mixed by grind process.
Then the mixture was annealed in N atmosphere at 950°C for 60 min and the final
2
product was obtained. Scheme1 shows the illustration of the in situ formation of typical
NFeꢀCNT/CMK3 nanocomposite.
4

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Scheme 1. Illustration of the preparation of the typical NFeꢀCNT/CMK3
Preparation of N- and Fe-doped Carbon Nanotube (NFe-CNT). NFeꢀCNT was
made through the same steps as CMK3/CNTꢀNꢀFe without adding CMK3 in the
process.
Preparation of Fe-doped CMK3 (Fe-CMK3). FeꢀCMK3 was made through the same
steps as CMK3/CNTꢀNꢀFe without adding melamine in the process.
Preparation of N-doped CMK3 (N-CMK3). NꢀCMK3 was made through the same
3
steps as CMK3/CNTꢀNꢀFe without adding FeCl in the process.
Characterization. A JEMꢀ2100F with an EDX analytical system was used to record
the scanning transmission electron microscopy (STEM) images. STEM samples were
prepared by dropꢀdrying the products onto copper grids. Scanning electron microscopy
(
SEM) images were obtained on a field emission scanning electron microanalyzer
JEOLꢀ6700F). SEM samples were prepared by dropꢀdrying the samples onto silicon
(
substrates. BET surface area was measured with a Micrometrics ASAP2020 analyzer
USA). Xꢀray photoelectron spectroscopic (XPS) results were obtained from an Xꢀray
(
photoelectron spectrometer (ESCALab MKII). Raman spectra were taken by an
inViaꢀReflex spectrometer (Renishaw) with a 532 nm laser excitation.
Electrochemical measurements.
CHI 730E electrochemical workstation (Shanghai Chenhua, China) was used to test the
electrocatalytical abilities for ORR. A platinum plate was used as counter electrode and
Ag/AgCl was used as reference electrode. The ORR tests were carried out in
O
2
ꢀsaturated 0.5 M H
2
SO
4
solution at room temperature. In the rotating disk electrode
5

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(RDE) measurements, the working electrode is a glassy carbon (GC) disk with a
diameter of 5 mm. For each sample (including the commercial 20 % Pt/C), 10.0 mg of
the sample was dispersed in the ethanol solution (5.0 mL) and ultrasonically for 40 min.
Then, 12.0 ꢁL of this suspension was dropped and adhered on the GC disk electrode
1
0,17
using Nafion solution.
catalyst and electrode were prepared by the same method as RDE. Pt ring electrode was
polarized at 850 mV (vs / RHE) in O ꢀsaturated 0.5 M H SO
In the rotating ringꢀdisk electrode (RRDE) measurements,
2
2
4
.
The calibration of Ag/AgCl electrode was performed in a standard threeꢀelectrode
system with polished Pt wires as the working and counter electrodes, and the Ag/AgCl
electrode as the reference electrode. Electrolytes are preꢀpurged and saturated with high
17
2 2 4
purity H . In 0.5 M H SO , E (RHE) = E (Ag/AgCl) + 0.23 V.
Results and discussion
The representative SEM and TEM images of the typical NFeꢀCNT/CMK3 were shown
in the Fig. 1a and Fig. S2 (see Supporting Information). These results clearly revealed
the typical NFeꢀCNT/CMK3 contains CMK3 and carbon nanotubes with the diameter
from 100 to 230 nm. STEM image of the typical NFeꢀCNT/CMK3 were shown in the
Fig. 1b. From the element mapping (Fig. 1cꢀf), the product contains carbon, oxygen,
nitrogen and ferrum elements. Fig. S3a and b (see Supporting Information) shows the
elemental analysis data in the square region marked with 1 and 2 in the Fig. 1b,
respectively. The product in the square region marked with 1 and 2 was doped by the
nitrogen and ferrum elements, respectively. However, the square region marked with 2
6

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contains higher nitrogen and ferrum content than that marked with 1. The SEM images
also indicate that the CMK3 and carbon nanotubes can produce a threeꢀdimension
interpenetrated network structure.
Fig. 1. (aꢀb) SEM and STEM images of the typical NFeꢀCNT/CMK3; (cꢀf) carbon,
oxygen, nitrogen, ferrum and element mapping.
XPS fullꢀscale spectrum of the typical NFeꢀCNT/CMK3 and the highꢀresolution N1s
XPS spectrum were shown in the Fig. 2aꢀb. From the Fig. 2a, the product contains
carbon, oxygen, nitrogen and ferrum elements. Fig. 2b indicates three kinds of nitrogen
were doped. The peak at 398.1 eV can be ascribed to pyridinic N species, the peak at
400.2 eV can be ascribed to pyrrolic structure and the peak at 401.2 eV corresponds to
1
0,17
the graphitic N.
According to the XPS data, 2.73 at.% of the N and 0.30 at.% of the
adsorption–desorption
Fe were doped in the typical product. Fig. 2c shows the N
2
isotherms. The BET surface area, total pore volume and micropore volume of the
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2
−1
3
−1
3
−1
typical product was 862.00 m g , 0.53 cm g and 0.33 cm g , respectively.
Raman spectra (Fig. 2d) show that the typical product exhibits the remarkable peaks at
ꢀ1
around 1335 and 1588 cm corresponding to the D band and G band, respectively. In
ꢀ1
addition, a broader 2D peak appeared at around 2850 cm .
Fig. 2. (a) XPS fullꢀscale spectrum; (b) highꢀresolution N1s XPS spectrum; (c)
adsorptionꢀdesorption isotherm and (d) Raman spectra of the typical NFeꢀCNT/CMK3.
We also prepared the NꢀCMK3, FeꢀCMK3 and NFeꢀCNT. SEM images of these
samples were shown in the Fig. 3. From the Fig. 3a, the NFeꢀCNT mainly contains
carbon nanotubes with the diameter from 30 to 50 nm. From the Fig. 3b and c,
NꢀCMK3 and FeꢀCMK3 contain the mesoporous carbon without carbon nanotubes,
respectively. Fig. S4 (see Supporting Information) shows the XPS fullꢀscale spectra of
the NꢀCMK3, FeꢀCMK3 and NFeꢀCNT samples. From the Fig. S4, the NꢀCMK3 was
doped by nitrogen, FeꢀCMK3 was doped by ferrum and NFeꢀCNT was doped by
8

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nitrogen and ferrum elements. In addition, we also prepared the product by
simply mixing the raw reagents of melamine, CMK3, and FeCl , without the subsequen
3
t pyrolysis. The product was denoted as mixture product. The XPS fullꢀscale spectrum
and highꢀresolution N1s XPS spectrum were shown in the Fig. S5a and b (see
Supporting Information). According to the XPS data, the mixture product contains the
60.61 at.% of the C, 34.71 at.% of the N, 4.14 at.% of the O,and 0.54 at.% of the Fe.
The N1s XPS peak of the mixture product comes from the raw materials of melamine.
Fig. 3. SEM images of the NFeꢀCNT (a), NꢀCMK3 (b) and FeꢀCMK3 (c)
3
We also prepared the products when the different FeCl (3, 4, 10 and 15 mg) were
added in the preparation. These products were denoted with NFeꢀCNT/CMK3ꢀ3mg,
NFeꢀCNT/CMK3ꢀ4mg, NFeꢀCNT/CMK3ꢀ10mg and NFeꢀCNT/CMK3ꢀ15mg. Fig. 4
shows the SEM images of the samples. From the Fig. 1 and 4, controlling the
appropriate ratio of FeCl to CMK3 content is crucial in the produce of the carbon
3
nanotube. When the ratio of FeCl
3
to CMK3 (w/w) is 1/10, the typical product has more
carbon nanotubes than others.
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Fig. 4. SEM images of the NFeꢀCNT/CMK3ꢀ3mg (a), NFeꢀCNT/CMK3ꢀ4mg (b),
NFeꢀCNT/CMK3ꢀ10mg (c) and NFeꢀCNT/CMK3ꢀ15mg (d)
Electrocatalytic activities
We tested the ORR activities of the samples in the acidic media (0.5 M H
2 4
SO ). ORR
activities were measured by rotating disk electrode (RDE) and rotating ringꢀdisk
1
7
electrode (RRDE) technologies. For comparison, commercial platinum (20 wt %) on
carbon black (Pt/C) (Johnson Matthey) was also tested. Fig. 5 shows the ORR results.
From the Fig. 5a, for the typical product and Pt/C, the value of onset potential was
803.0 and 871.0 mV (vs RHE), respectively. Obviously, the value of onset potential and
halfꢀpeak potential of the typical product is only 68.0 mV and 63.0 mV less than that of
the Pt/C, respectively. When the potential is lower than 670.0 mV (vs RHE), the current
density of the typical product electrode is remarkably larger than that of commercial
Pt/C.
For the NFeꢀCNT, NꢀCMK3 and FeꢀCMK3, the value of onset potential was 730, 670,
1
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and 685 mV (vs RHE), respectively. For the NFeꢀCNT/CMK3, NꢀCMK3, FeꢀCMK3
and NFeꢀCNT, the typical NFeꢀCNT/CMK3 shows the highest value of onset and
halfꢀpeak potential and largest reduce current. So far, though many ORR catalysts have
shown the excellent activity and durability in alkaline solution, it remains a great
challenge to achieve the excellent ORR activity and durability in acidic media.
According to the reported literature, the typical product exhibits the very high ORR
2
,5,13,14,16,19,21,24,35
activity and excellent durability in acidic media.
RDE voltammograms
for the ORR on the typical product at the various rotation speeds (from 400 to 2000 rpm)
was shown in the Fig. 5b. RDE voltammograms on the Pt/C, NꢀCMK3, FeꢀCMK3 and
NFeꢀCNT at the various rotation speeds (from 400 to 2000 rpm) was shown in the Fig.
6aꢀd. From the Fig. 5b and Fig. 6a, the halfꢀpeak potential of the typical product is only
59, 61, 62, 63.0 and 65 mV less than that of the Pt/C at the rotation speeds from 400 to
2000 rpm, respectively. From the Fig. 5b and Fig. 6bꢀd, the typical NFeꢀCNT/CMK3
also shows the higher value of onset and halfꢀpeak potential and larger reduce current at
the rotation speeds from 400 to 2000 rpm than the NꢀCMK3, FeꢀCMK3 and NFeꢀCNT,
respectively.
An ideal ORR catalyst should have satisfactory tolerance to the fuel molecules. In this
work, methanol poisoning effects of the typical product and commercial Pt/C were
investigated. We measured the poisoning effects of the typical NFeꢀCNT/CMK3 in
O
2
ꢀsaturated 0.5 M H
were shown in the Fig. 5c. We also measured the poisoning effects of the Pt/C in
ꢀsaturated 0.5 M H SO with 1.0 M methanol (shown in the Fig. S6, see Supporting
2 4
SO with 0.5, 1.5 and 3.0 M methanol, respectively. The results
O
2
2
4
11

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Information). Compared to Pt/C, the typical product shows little activity loss, which
indicates that the typical product has excellent tolerance to methanol poisoning effects.
The typical NFeꢀCNT/CMK3 still has excellent tolerance to the methanol in
O ꢀsaturated 0.5 M H SO with 3.0 M methanol. Durability of the typical
2
2
4
NFeꢀCNT/CMK3 and Pt/C was measured by the currentꢀtime (iꢀt) chronoamperometric
response. The results were shown in the Fig. 5d. After 10000 seconds, the Pt/C suffered
from a 22.5 % loss in current density while the typical product showed the 18.8 %
decrease of current density, which indicates the NFeꢀCNT/CMK3 has a better durability
than the Pt/C.
Fig. 5. RDE results in 0.5 M H SO . (a) RDE voltammograms in O ꢀsaturated 0.5 M
2
4
2
−
1
H SO at room temperature (rotation speed 1600 rpm, sweep rate 20 mV s ) for the
2
4
typical NFeꢀCNT/CMK3, NꢀCMK3, FeꢀCMK3, NFeꢀCNT and Pt/C; (b) RDE
voltammograms for the ORR at the typical NFeꢀCNT/CMK3 electrode at the various
−
1
rotation speeds (sweep rate 20 mV s ); (c) RDE voltammograms in O
2
ꢀsaturated 0.5
−1
M H SO at room temperature (rotation speed 1600 rpm, sweep rate 20 mV s ) for
2
4
the typical NFeꢀCNT/CMK3 with or without methanol; (d) Currentꢀtime (iꢀt)
chronoamperometric response of the typical NFeꢀCNT/CMK3 and Pt/C electrodes at
1
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2 2 4
ꢀ0.65 V (vs Hg/HgO) in O ꢀsaturated 0.5 M H SO at a rotation rate of 700 rpm.
Fig. 6. (aꢀd) RDE voltammograms for the ORR at the Pt/C，FeꢀCMK3, NꢀCMK3 and
−1
NFeꢀCNT electrode at the various rotation speeds (sweep rate 20 mV s )
Effect of the Fe content, annealing temperature and time on the ORR activity were
investigated. The results were shown in the Fig.7. Fig.7a shows the effect of Fe content
3
on the ORR activity. From the Fig. 7a, the optimal FeCl amount is 6 mg in the typical
o
o
preparation. We also prepared the products when the temperature is 850 C, 950 C and
o
1
000 C in the preparation, respectively. These products were denoted with
NFeꢀCNT/CMK3ꢀ850, NFeꢀCNT/CMK3ꢀ950 and NFeꢀCNT/CMK3ꢀ1000. Fig. 7b
shows the effect of annealing temperature on the ORR activity. Fig. 7c shows the effect
o
of annealing time (when the temperature is 950 C) on the ORR activity. From the Fig.
1
3

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o
7
bꢀc, the optimal annealing temperature and time is 950 C and 60 min. From the Fig. 7,
we can easily draw a conclusion that Fe content, annealing temperature and annealing
time can obviously affect the ORR activity.
Fig. 7. (a) RDE voltammograms in O ꢀsaturated 0.5 M H SO at room temperature
2
2
4
−
1
(
rotation speed 1600 rpm, sweep rate 20 mV s ) for the NFeꢀCNT/CMK3ꢀ3mg，
NFeꢀCNT/CMK3ꢀ4mg, NFeꢀCNT/CMK3ꢀ6mg and NFeꢀCNT/CMK3ꢀ10mg; (b) RDE
voltammograms in O ꢀsaturated 0.5 M H SO at rotation speed 1600 rpm, for the
2
2
4
NFeꢀCNT/CMK3ꢀ850, NFeꢀCNT/CMK3ꢀ950 and NFeꢀCNT/CMK3ꢀ1000; (c) RDE
voltammograms in O ꢀsaturated 0.5 M H SO at rotation speed 1600 rpm, for the
2
2
4
NFeꢀCNT/CMK3ꢀ40min, NFeꢀCNT/CMK3ꢀ60min and NFeꢀCNT/CMK3ꢀ80min
The selectivity of the fourꢀelectron reduction of oxygen on the typical NFeꢀCNT/CMK3
and Pt/C was investigated by the RRDE technology. The fourꢀelectron selectivity was
2 2 2 2
evaluated based on the H O yield. The H O yield and the electron transfer number (n)
were determined by the following equations:
/ N
+ I / N
(2)
IR
%(H
2O
2
) = 200×
(1)
ID
R
I
D
n = 4× ID
+ I
R
/ N
where I
D
is the disk current, and I
R
is the ring current, and N is current collection
Fe[CN]
Fig. 8 shows the RRDE voltammograms for the typical NFeꢀCNT/CMK3, from which
7,17
efficiency of the Pt ring. N is 0.35 from the reduction of K
3
6
.
1
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the peroxide yield and electron transfer number were obtained (Fig. 8b). The peroxide
yield remained below 0.5 % at the potentials from 0.05ꢀ1.0 V (versus RHE) and
electron transfer number was calculated to be 3.90ꢀ4.00, which reveals an intrinsic
fourꢀelectronꢀtransfer process. For the Pt/C (Fig. 8c and d), the peroxide yield remained
below 4.0 % at the potentials from 0.05ꢀ1.0 V (versus RHE) and electron transfer
number was calculated to be 3.95ꢀ4.00.
Fig. 8. RRDE results for the typical NFeꢀCNT/CMK3 and Pt/C. (a) RRDE
voltammograms for the ORR at the typical NFeꢀCNT/CMK3 electrode in O
2
ꢀsaturated
−
1
0
.5 M H SO . The electrode rotation speed was 1600 rpm, sweep rate was 20 mV s ;
2
4
(
8
H
b) The electron transfer number (n) and peroxide yield obtained from RRDE curve Fig.
a; (c) RRDE voltammograms for the ORR at the Pt/C electrode in O ꢀsaturated 0.5 M
SO ; (d) The electron transfer number (n) and peroxide yield obtained from RRDE
curve Fig. 8c.
2
2
4
What is the reason for the excellent ORR activity of the NFeꢀCNT/CMK3 in acidic
1
5

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media? We believe that the NFeꢀCNT and NFeꢀCMK3 in the nanocomposite have the
synergistically enhanced electrochemical activities for ORR in acidic media. The
doping of the nitrogen and ferrum elements in the NFeꢀCNT/CMK3 can promote the
activity of ORR catalysts in acidic media, because the ferrum element can coordinate
with the nitrogen doped in the carbon materials so that the more active site can be
2
0,23,24
produced.
Combining the NFeꢀCMK3 with the NFeꢀCNT can form a
threeꢀdimension interpenetrated network structure, which can improve conductivity of
the nanocomposite and highly effectively accelerates reactant, ion and electron
10,17
transport.
In addition, the nanocomposite has large surface area so that it has many
catalytic sites for ORR on the surface, and the active sites can be easily exposed to
21,28,36,37
react.
Nowadays, CMKꢀ3 can be manufactured on the large scale at lowꢀcost and has become
the commercially available materials. The NFeꢀCNT/CMK3 nanocomposite can be
prepared by the simple and readily scalable procedure proposed by us. Therefore, this
work is of great importance in the developing of highꢀperformance nonꢀprecious metal
electrocatalysts with cheap and commercially available materials. Because the obtained
products have excellent catalytical ability in acidic media, they may have the practical
1
6,28,38,39
application of fuel cell.
In addition, because of the doping of nitrogen and
ferrum elements, threeꢀdimension interpenetrated network structure and large surface
area, the nanocomposite may have the broad applications in the other fields such as
removal of pollutant, gas uptake, supercapacitors, lithium ion batteries, sensors and so
on.
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RSC Advances
Page 18 of 20
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DOI: 10.1039/C5RA15487A
Conclusions
We developed a simple and readily scalable procedure to prepare the NFeꢀCNT/CMK3
3
+
nanocomposite. Trace Fe can catalyze the in situ growth of the Nꢀ and Feꢀdoped CNT
from the melamine as the precursor. The typical product shows excellent catalytic
ability for oxygen reduction reaction (ORR) in the acidic media. The value of onset
potential and halfꢀpeak potential of the typical product is only 68.0 mV and 63.0 mV
less than that of the commercial 20 % Pt/C catalyst, respectively. The product also
reveals superior stability and tolerance to methanol poisoning effects compared to the
Pt/C. As an ordered mesoporous carbon, CMKꢀ3 can be manufactured on the large scale
at lowꢀcost and has become the commercially available materials. This work is of great
importance in the developing of highꢀperformance nonꢀprecious metal electrocatalysts
with cheap and commercially available materials. Because the obtained products have
excellent catalytical ability in acidic media, they may have the practical application of
fuel cell.
Acknowledgements
We acknowledge the funding support from the National Natural Science Foundation of
China (Grants 21271005), Project of Anhui University (02303203ꢀ0054), the College
Students' Innovation and Entrepreneurship Training Project (J18515020)，the Natural
Science Foundation of Anhui Province (No.1308085QB35) and the Natural Science
Foundation of Education Department of Anhui Province (No. KJ2015A232).
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Page 19 of 20
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DOI: 10.1039/C5RA15487A
References
1.
2.
3.
4.
5.
6.
B. C. H. Steele and A. Heinzel, Nature, 2001, 414, 345ꢀ352.
Y. H. Bing, H. S. Liu, L. Zhang, D. Ghosh and J. J. Zhang, Chem. Soc. Rev., 2010, 39, 2184ꢀ2202.
R. Bashyam and P. Zelenay, Nature, 2006, 443, 63ꢀ66.
R. B. Levy and M. Boudart, Science, 1973, 181, 547ꢀ549.
M. K. Debe, Nature, 2012, 486, 43ꢀ51.
F. Jaouen, E. Proietti, M. Lefevre, R. Chenitz, J. P. Dodelet, G. Wu, H. T. Chung, C. M. Johnston
and P. Zelenay, Energ. Environ. Sci., 2011, 4, 114ꢀ130.
7
1
8
9
7
1
.
Y. Y. Liang, Y. G. Li, H. L. Wang, J. G. Zhou, J. Wang, T. Regier and H. J. Dai, Nat. Mater., 2011,
0, 780ꢀ786.
.
.
H. T. Chung, J. H. Won and P. Zelenay, Nat. Commun., 2013, 4,
P. Chen, T. Y. Xiao, H. H. Li, J. J. Yang, Z. Wang, H. B. Yao and S. H. Yu, Acs Nano, 2012, 6,
12ꢀ719.
0. P. Chen, T. Y. Xiao, Y. H. Qian, S. S. Li and S. H. Yu, Adv. Mater., 2013, 25, 3192ꢀ3196.
11. S. J. Guo, S. Zhang, L. H. Wu and S. H. Sun, Angew. Chem. Int. Edit., 2012, 51, 11770ꢀ11773.
1
2
1
3
1
1
1
1
2. Y. Y. Liang, H. L. Wang, J. G. Zhou, Y. G. Li, J. Wang, T. Regier and H. J. Dai, J. Am. Chem. Soc. ,
012, 134, 3517ꢀ3523.
3. C. Medard, M. Lefevre, J. P. Dodelet, F. Jaouen and G. Lindbergh, Electrochim. Acta., 2006, 51,
202ꢀ3213.
4. J. Tian, L. Birry, F. Jaouen and J. P. Dodelet, Electrochim. Acta., 2011, 56, 3276ꢀ3285.
5. F. Charreteur, F. Jaouen, S. Ruggeri and J. P. Dodelet, Electrochim. Acta., 2008, 53, 2925ꢀ2938.
6. G. Wu and P. Zelenay, Acc. Chem. Res., 2013, 46, 1878ꢀ1889.
7. P. Chen, L. K. Wang, G. Wang, M. R. Gao, J. Ge, W. J. Yuan, Y. H. Shen, A. J. Xie and S. H. Yu,
Energ. Environ. Sci., 2014, 7, 4095ꢀ4103.
1
8. Y. Zheng, Y. Jiao, M. Jaroniec, Y. G. Jin and S. Z. Qiao, Small, 2012, 8, 3550ꢀ3566.
1
9. Y. G. Li, W. Zhou, H. L. Wang, L. M. Xie, Y. Y. Liang, F. Wei, J. C. Idrobo, S. J. Pennycook and H.
J. Dai, Nat. Nanotechnol., 2012, 7, 394ꢀ400.
2
2
1
2
2
0. M. Lefevre, E. Proietti, F. Jaouen and J. P. Dodelet, Science, 2009, 324, 71ꢀ74.
1. H. W. Liang, W. Wei, Z. S. Wu, X. L. Feng and K. Mullen, J. Am. Chem. Soc., 2013, 135,
6002ꢀ16005.
2. G. Wu, K. L. More, C. M. Johnston and P. Zelenay, Science, 2011, 332, 443ꢀ447.
3. U. I. Kramm, J. Herranz, N. Larouche, T. M. Arruda, M. Lefevre, F. Jaouen, P. Bogdanoff, S.
Fiechter, I. AbsꢀWurmbach, S. Mukerjee and J. P. Dodelet, Phys. Chem. Chem. Phys., 2012, 14,
1673ꢀ11688.
4. H. L. Peng, Z. Y. Mo, S. J. Liao, H. G. Liang, L. J. Yang, F. Luo, H. Y. Song, L. Zhong and B. Q.
Zhang, Sci. Rep-Uk, 2013, 3,
1
2
25. F. Jaouen, F. Charreteur and J. P. Dodelet, J. Electrochem. Soc., 2006, 153, A689ꢀA698.
26. K. P. Gong, F. Du, Z. H. Xia, M. Durstock and L. M. Dai, Science, 2009, 323, 760ꢀ764.
27. J. Y. Cheon, T. Kim, Y. Choi, H. Y. Jeong, M. G. Kim, Y. J. Sa, J. Kim, Z. Lee, T. H. Yang, K.
Kwon, O. Terasaki, G. G. Park, R. R. Adzic and S. H. Joo, Sci. Rep-Uk, 2013, 3,
2
2
8. J. Wang, H. L. Xin and D. L. Wang, Part. Part. Syst. Char., 2014, 31, 515–539.
9. S. Jun, S. H. Joo, R. Ryoo, M. Kruk, M. Jaroniec, Z. Liu, T. Ohsuna and O. Terasaki, J. Am. Chem.
Soc., 2000, 122, 10712ꢀ10713.
1
8

RSC Advances
Page 20 of 20
View Article Online
DOI: 10.1039/C5RA15487A
3
0. J. Tang, T. Wang, X. Sun, Y. Y. Hu, Q. Q. Xie, Y. X. Guo, H. R. Xue and J. P. He, Electrochim.
Acta., 2013, 90, 53ꢀ62.
3
2
3
3
2
3
6
3
3
3
3
1. X. J. Huang, Y. G. Tang, L. F. Yang, P. Chen, Q. S. Wu and Z. Pan, J. Mater. Chem. A, 2015, 3,
978ꢀ2984.
2. Z. Y. Wu, P. Chen, Q. S. Wu, L. F. Yang, Z. Pan and Q. Wang, Nano Energy, 2014, 8, 118ꢀ125.
3. W. J. Yuan, J. C. Li, A. J. Xie, P. Chen, S. K. Li and Y. H. Shen, Electrochim. Acta., 2015, 165,
9ꢀ35.
4. W. J. Yuan, J. C. Li, L. K. Wang, P. Chen, A. J. Xie and Y. H. Shen, Acs. Appl. Mater. Inter., 2014,
, 21978ꢀ21985.
5. C. Z. Zhu and S. J. Dong, Nanoscale, 2013, 5, 1753ꢀ1767.
6. L. M. Dai, D. W. Chang, J. B. Baek and W. Lu, Small, 2012, 8, 1130ꢀ1166.
7. H. Wang, X. J. Bo, Y. F. Zhang and L. P. Guo, Electrochim. Acta., 2013, 108, 404ꢀ411.
8. J. Tian, A. Morozan, M. T. Sougrati, M. Lefevre, R. Chenitz, J. P. Dodelet, D. Jones and F. Jaouen,
Angew. Chem. Int. Edit., 2013, 52, 6867ꢀ6870.
3
9. J. Liu, X. J. Sun, P. Song, Y. W. Zhang, W. Xing and W. L. Xu, Adv. Mater., 2013, 25, 6879ꢀ6883.
1
9