Antimony-Based Composites Loaded on Phosphorus-Doped Carbon for Boosting Faradaic Efficiency of the Electrochemical Nitrogen Reduction Reaction

Article abstract of DOI:10.1002/anie.201906521

A nanocomposite of PC/Sb/SbPO₄ (PC, phosphorus-doped carbon) exhibits a high activity and an excellent selectivity for efficient electrocatalytic conversion of N₂ to NH₃ in both acidic and neutral electrolytes under ambient conditions. At a low reductive potential of ?0.15 V versus the reversible hydrogen electrode (RHE), the PC/Sb/SbPO₄ catalyst achieves a high Faradaic efficiency (FE) of 31 % for ammonia production in 0.1 m HCl under mild conditions. In particular, a remarkably high FE value of 34 % is achieved at a lower reductive potential of ?0.1 V (vs. RHE) in a 0.1 m Na₂SO₄ solution, which is better than most reported electrocatalysts towards the nitrogen reduction reaction (NRR) in neutral electrolyte under mild conditions. The change in surface species and electrocatalytic performance before and after N₂ reduction is explored by an ex situ method. PC and SbPO₄ are both considered as the active species that enhanced the performance of NRR.

Full text of DOI:10.1002/anie.201906521

A Journal of the Gesellschaft Deutscher Chemiker
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Accepted Article
Title: Antimony-Based Composites Loading on Phosphorus-Doped
Carbon for Boosting Faradaic Efficiency of the Electrochemical
Nitrogen Reduction Reaction
Authors: Xien Liu, Haeseong Jang, Ping Li, Jia Wang, Qing Qin, Min
Gyu Kim, Guangkai Li, and Jaephil Cho
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201906521
Angew. Chem. 10.1002/ange.201906521
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Angewandte Chemie International Edition
10.1002/anie.201906521
COMMUNICATION
Antimony-Based Composites Loading on Phosphorus-Doped
Carbon for Boosting Faradaic Efficiency of the Electrochemical
Nitrogen Reduction Reaction
[
a]
[b]
[a]
[a]
[a]
[c]
[a]
Xien Liu,* Haeseong Jang, Ping Li, Jia Wang, Qing Qin,* Min Gyu Kim, Guangkai Li, and
Jaephil Cho*[b]
Abstract: The ammonia synthesis from nitrogen by electrochemical
route with high selectivity on a large scale at room temperature and
atmospheric pressure is highly desirable but challenging. Herein, a
is limited by their expensive and rare attributes. Compared to
noble metal-based catalysts, non-noble metal-based and metal-
/GCE,[ Fe
3]
O
-CNT, polymeric
[4]
free catalysts, such as MoO
3
2
3
carbon nitride (PCN)[5] and nitrogen-doped carbon nanospikes,
are earth abundant and more favorable due to their low cost and
high FE. To suppress the competitive hydrogen evolution reaction
(HER), the use of an organic electrolyte, particularly an ionic liquid,
was demonstrated to be highly effective. Using 1-butyl-1-
methylpyrrolidinium tris (pentafluoroethyl) trifluorophosphate
[6]
new nanocomposite of PC/Sb/SbPO
carbon) exhibits a high activity and an excellent selectivity for efficient
electrocatalytic conversion of N to NH in both acidic and neutral
electrolytes under ambient conditions. At a low reductive potential of
0.15 V versus the reversible hydrogen electrode (RHE), the
PC/Sb/SbPO catalyst achieves a high Faradaic efficiency (FE) of
1 % for ammonia production in 0.1 M HCl under mild conditions. In
particular, a remarkably high FE value of 34 % is achieved at a lower
reductive potential of - 0.1 V (vs. RHE) in a 0.1 M Na SO solution,
4
(PC, phosphorus-doped
2
3
-
4
3
([C
4
mpyr] [eFAP]) as the electrolyte, MacFarlane et al. reported
NRR catalyst exhibited an excellent FE of
that an α-Fe@Fe
3
O
4
2
4
32 %, which was further enhanced up to 60 % by using an ionic
liquid as the electrolyte.[7] Obviously, however, the use of an ionic
liquid is not economic and sustainable.
which is better than most reported electrocatalysts towards nitrogen
reduction reaction (NRR) in neutral electrolyte under mild conditions.
The change in surface species and electrocatalytic performance
Very recently, Hao et.al. reported a strategy for promoting
NRR selectivity and activity by using bismuth nanocrystals and
potassium cations, leading to a record high FE of 66 % in acid
electrolyte.[8] Thus, one of the attractive options is to develop
composite catalysts of a high FE and selectivity for NRR. For this
purpose, antimony-based and carbon-based materials are
attractive components of choice as they are not highly active for
the HER, and hence good for NRR. Besides, carbon-based
nanomaterials, such as PCN and nitrogen-doped carbon
nanospikes, have demonstrated FEs beyond 10 %. However,
PCN itself contains C-N bonds, which are more easily broken than
2
before and after N reduction is explored by ex-situ method. PC and
SbPO are both considered as the active species that enhanced the
4
performance of NRR.
Scientists have been developing novel ammonia synthetic routes
under mild conditions to replace the energy-intensive, harmful
and unsustainable Haber-Bosch process. Ammonia synthesis by
electrocatalytic NRR at room temperature and atmospheric
pressure is considered a promising route and has become a very
hot research topic.[1] Noble metal-based materials are commonly
used to catalyze the NRR. In this context, Zeng et al. reported that
the Ru single-atom catalyst, Ru SAs/N-C, exhibited a FE of
the triple bond of N
Although isotopic labeling measurements using
have been used to examine the actual N source of NH
2
to affect the yield rate of ammonia and FE.
15
2
N -enriched gas
, this
3
2
9.6 % for ammonia synthesis at - 0.20 V (vs. RHE) under
technique is expensive and not available at all laboratories.
Therefore, it highly desirable to develop antimony- and carbon-
based N-free composite materials that can achieve a high FE and
selectivity for ammonia synthesis, though antimony- and carbon-
based composite containing with or without N has yet to be
reported in the literature.
[
2]
ambient conditions, and the Ru single atoms were considered
to be the key active sites. Very recently, Sun’s group also reported
a Ru single-atom catalyst, Ru@ZrO
rate of ammonia up to 3.66 mgNH3h mgRu at a potential of - 0.21
V. However, the use of noble metal-based catalysts in large-scale
2
1
/NC, that enhanced the yield
-
-1
In this study, we synthesized the first NRR electrocatalyst
composed of PC/Sb/SbPO that achieved a high FE of 31 % at a
4
[
[
[
a]
b]
c]
Prof. X. Liu, P. Li, J. Wang, Dr. Q. Qin, G. Li,
State Key Laboratory Base of Eco-Chemical Engineering, College of
Chemical Engineering, College of Chemistry and Molecular
Engineering, Qingdao University of Science and Technology
Qingdao 266042, China
E-mail: liuxien@qust.edu.cn; qinqing@qust.edu.cn
H. Jang, Prof. J. Cho
Department of Energy Engineering and School of Energy and
Chemical Engineering, Ulsan National Institute of Science and
Technology (UNIST)
Ulsan 689-798, South Korea
E-mail: jpcho@unist.ac.kr
Prof. M. Kim
Beamline Research Division, Pohang Accelerator Laboratory (PAL)
Pohang 790-784, Korea
low reductive potential of - 0.15 V (vs. RHE) and a high ammonia
yield rate of 25 µg h-1 mgcat.-1 at - 0.25 V in 0.1 M HCl under
ambient conditions. In neutral electrolytes, the catalyst
outperformed all reported non-noble metal-based catalysts for the
conversion of N
low reductive potential of - 0.1 V. Our ex-situ electrochemical
study indicated that PC and SbPO were both served as the active
sites for enhancing the NRR performance of PC/Sb/SbPO
PC/Sb/SbPO was prepared by annealing C/Sb/Sb
sodium hypophosphite monohydrate under an argon atmosphere
see Supporting Information for details). Figure S1 shows the X-
ray diffraction (XRD) pattern for the C/Sb/Sb . A typical
2 3
to NH with a remarkably high FE of 34 % at a
4
4
.
4
2 3
O and
(
2
O
3
scanning electron microscopy (SEM) image in Figure 1a shows
the three-dimensional honeycomb structure of the as-synthesized
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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COMMUNICATION
PC/Sb/SbPO
black plot) of the as-prepared catalyst can be well indexed to
rhombohedral Sb (green plot at the bottom of Figure 1b, JCPDS
No. 05-0562) and monoclinic SbPO (red plot at the bottom of
4
catalyst. As shown in Figure 1b, all the XRD peaks
survey spectrum and the high-resolution XPS spectrum of N 1s
(Figure S5b). The Sb 3d core level XPS spectrum of the as-
(
prepared PC/Sb/SbPO
4
in Figure 2a (plots at the bottom) was
4
deconvoluted into two peaks located at 530.3 eV and 539.7 eV,
Figure 1b, JCPDS No.35-0829). The characteristic peaks of PC
are not present, which may be caused by the poor crystallinity of
which can be assigned to Sb 3d5/2 and Sb 3d3/2 of SbPO
4
,
respectively, corresponding to the Sb(III) state.[ However, no Sb0
peaks, which should be located at approximately 537.5 and 528.2
eV for Sb 3d3/2 and Sb 3d5/2,[10] are observed, indicating that the
9]
the carbon substrate relative to that of Sb and SbPO
reduction at - 0.15 V (vs. RHE) in 0.1 M HCl for 1 h, the diffraction
peaks corresponding to SbPO disappeared, and the peaks in
Figure 1b highlighted by the green lines can be attributed to
metallic Sb, which may be caused by partial dissolution of SbPO
into the electrolyte and amorphization upon NRR. As shown in
Figure S2, the HRTEM image of PC/Sb/SbPO after the NRR
4 2
. After N
4
4
metallic Sb is covered by SbPO and is consistent with the
HRTEM result. The small peak at a binding energy (BE) of 531.8
eV can be ascribed to O 1s.[ After the NRR testing, as shown in
Figure 2a (plots at the top), the peaks of Sb 3d5/2 and Sb 3d3/2 are
slightly shifted to higher binding energies, indicating the formation
of Sb species with a higher valence state on the surface of the
catalyst.[ After the NRR testing, two peaks appeared at BEs of
402.5 eV and 400.3 eV in N 1s spectrum (Figure S5c) can be
9]
4
4
testing shows blurred lattice fringes, and the contents of elemental
Sb, P and O decreased obviously after the NRR measurement
11]
(
Figure S3). The high-resolution transmission electron
microscopy (HRTEM) image of the catalyst is shown in Figure 1c,
which corresponds to the region marked with a white circle in
Figure S4. The clear fringe with a lattice spacing of 0.33 nm can
assigned to NH
production of NH
2
and NH
is from N
4
+,[12] respectively, indicating the
, instead of other NH source in
3
2
3
reaction vessel. The P 2p spectrum in Figure 2b can be
deconvoluted into two components at BEs of 133.0 and 134.0 eV,
corresponding to P 2p3/2 and P 2p1/2 for the P-C and P-O bonds in
4
be indexed to the (101) plane of SbPO . The energy-dispersive
X-ray spectroscopy (EDS) analysis in Figure 1d-h further confirms
the component of the prepared catalyst and the uniform
distribution of C, Sb, P and O in the structure.
P-doped carbon and SbPO
the relative contents of P-O and P-C were obviously changed,
further confirming the content decrease of SbPO in the hybrids.
4
,[13] respectively. After N
2
reduction,
4
By contrast, the BEs of C=O/P=O and C-O-P in O 1s spectra
display almost no shift after the NRR testing (Figure S5d). The
peaks centered at 284.4 eV and 286.2 eV in C 1s spectrum
(
Figure S5e) can be assigned to C=C and C-P interactions,
respectively.[ After the NRR testing, three new peaks were
observed at approximately 290-293 eV, belonging to the C
species in the Nafion binder introduced for the electrochemical
measurements. Otherwise, the BEs of C=C and C-P have no
obvious change before and after the NRR testing.
14]
Figure 1. a) SEM image of PC/Sb/SbPO
before and after NRR testing. The vertical bars in the bottom corresponded to
the XRD standard cards (red plot: SbPO , green plot: Sb). c) HRTEM image of
PC/Sb/SbPO . d-h) STEM-EDS elemental mapping of PC/Sb/SbPO
4 4
. b) XRD patterns of PC/Sb/SbPO
4
4
4
.
X-ray photoelectron spectroscopy (XPS), X-ray absorption
near-edge structure (XANES) and extended X-ray absorption fine
structure spectroscopy (EXAFS) measurements were conducted
to further verify the composition and electronic states of
Figure 2. a) High-resolution XPS spectra of Sb 3d for PC/Sb/SbPO
spectrum shown at the bottom refers to the as-prepared samples, while the one
shown at top corresponds to the samples after N reduction at -0.15 V (vs. RHE)
in 0.1 M HCl for 1 h. b) High-resolution XPS spectra of P 2p before and after N
4
. The
2
2
reduction. c) The XANES spectra of PC/Sb/SbPO
d) The k -weighted Fourier transform of EXAFS spectra of PC/Sb/SbPO
4
before and after N
2
reduction.
before
2
PC/Sb/SbPO
are observed in the XPS survey spectrum of PC/Sb/SbPO
Before N reduction, no N signal is observed both in the XPS
4
. As demonstrated by Figure S5a, C, O, P and Sb
4
.
2
and after N reduction.
4
2
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COMMUNICATION
yield rate of 25 μg h-1 mgcat for ammonia was obtained at a
-1
4
The XANES spectrum of Sb K-edge for PC/Sb/SbPO (red
plot in Figure 2c) shows a main peak at 30502 eV, which is similar
to that of reported Sb3+ species. After the NRR testing, the main
peak slightly shifted to a higher photon energy (blue plot in Figure
potential of - 0.25 V (vs. RHE). The FE of the PC/Sb/SbPO
catalyst for ammonia production reached 31 % at a low applied
potential of - 0.15 V, which even exceeded those of some noble
4
[15]
2
c), indicating the appearance of Sb species with a higher valence
metal-based catalysts, including Au/CeO
vs. RHE),[17] Au/TiO
(8.11 % at - 0.2 V vs. RHE), Ru@ZrO /NC
2 2
(21 % at - 0.11 V vs. RHE), Ru SAs/N-C (29.6% at - 0.2 V vs.
RHE)[20] and Au SAs-NDPCs (12.3 % at - 0.2 V vs. RHE).[21]
x
-RGO (10.1 % at - 0.2 V
state on the surface of the catalyst,[16] which is consistent with the
XPS analysis result. The radial distribution function of
[18]
[19]
PC/Sb/SbPO
4
in Figure 2d shows the peaks centered at 0.98 and
1
.48 Å belonging to Sb-O bonds, while the adjacent peak featured
4
Notably, the PC/Sb/SbPO catalyst delivered an ammonia yield
rate of 16.7 μg h-1 mgcat. at - 0.15 V, which is over four times
-1
at 2.73 Å resulted from the Sb-Sb interaction. After the NRR, the
two peaks of the Sb-O bonds shifted to smaller interatomic
distances of 0.91 and 1.42 Å due to the formation of Sb species
with a higher valence state, while the interatomic distance of the
Sb-Sb bond increased and right-shifted to 2.76 Å. By combining
these advanced characteristic techniques, the prepared catalyst
-1
higher than that of C/Sb/Sb
2
O
3
(4.1 μg h-1 mgcat. ) (Figure 3c). In
contrast, without the Sb/SbPO
4
nanoparticles, PC delivers poorer
NRR activity, characterized by an smaller NH
3
formation rate of
7.4 μg h-1 mgcat. . Because of the coverage of Sb by SbPO
-1
0
layer,
4
0
the Sb species are not directly taking part in the catalytic process.
was unequivocally determined to be the PC/Sb/SbPO
nanocomposite, in which SbPO species covered the surface of
nanoparticles supported on P-
4
Hence, the PC and SbPO
synergistically enhance the NRR activity of the PC/Sb/SbPO
reported by previous studies, heteroatom P doping into carbon
4
are both the active sites for NRR,
4
4
. As
metallic Sb to form Sb/SbPO
doped carbon.
4
can effectively tailor the electron structure of carbon,[
significantly improving the conductivity of the catalyst. Moreover,
the SbPO nanoparticles anchored on the PC substrate can
14a, 22]
4
effectively prevent them from aggregation, favoring high stability
for long-term NRR process. The recycling tests were performed
at - 0.15 V (vs. RHE) for 1 h. The chronoamperometry results
were shown in Figure S9. Evidently, both the NH
FE have no obvious degradation experiencing five cycling tests
Figure 3d). As shown in Figure S10, the current density of
PC/Sb/SbPO remained stable during the continuous NRR at -
.15 V in acid media for 24 h because the current density of HER
was majority. However, the concentration of NH in the electrolyte
presented a nonlinear increase from the initial concentration of
3
yield rate and
(
4
0
3
.215 µg mL-1 at 6th h to 0.395 µg mL , 0.547 µg mL , and 0.658
-1
-1
0
µg mL-1 at 12th h, 18th h, and 24th h, respectively (Figure S11a),
and the corresponding yield rate of NH
3
exhibited a gradual
decrease from 12.55 µg h-1 mgcat. to 7.10 µg h-1 mgcat. after
consecutive electrolysis (Figure S11b), indicating a loss of the
NRR activity of 43 % after electrolysis for 24 h. The loss of the
-1
-1
Figure 3. a) Time-current density curves for PC/Sb/SbPO
for 3600 in 0.1 HCl. b) NH yields and Faradaic efficiencies for
PC/Sb/SbPO at corresponding potentials. c) NH yields of PC/Sb/SbPO
C/Sb/Sb and PC electrodes at potential of - 0.15 V (vs. RHE) after 1 h
electrolysis under ambient conditions. d) Recycling test of NH yields and
Faradaic efficiencies over PC/Sb/SbPO electrodes for five times at potential of
0.15 V (vs. RHE).
4
at different potentials
s
M
3
4
3
4
,
NRR activity of PC/Sb/SbPO
reasons: First, the loss of the active sites caused by the partial
dissolution of SbPO into electrolyte and amorphization; Second,
the N-contained species, NH bind to the catalyst (Figure S5c)
during the NRR process, making the catalyst deactivation; Third,
the NH formation reaction is a reversible reaction. When the
ammonia concentration reaches a certain value, the reaction is in
equilibrium, which also leads to the decrease of the NH yield rate.
We also quantified the hydrogen by gas chromatography (GC)
is attributed to three possible
4
2
O
3
3
4
4
-
x
3
The NRR testing were first performed in a 0.1 M HCl solution
under ambient conditions using a gas-tight H-type cell, which was
separated from the counter electrode by a Nafion 117 membrane.
Carbon paper coated with the catalyst was used as the cathode.
3
after NRR testing at - 0.15 V for 6 h and the FE of H
calculated to be 68.7 % (Figure S12), while the FE of NH
3
2
was
was
For comparison, the NRR activities of PC and PC/Sb/Sb
also tested under the same conditions. Figure S6a shows the
linear sweep voltammetry (LSV) curves of PC/Sb/SbPO in both
- and Ar-saturated 0.1 M HCl media. The larger current density
at a lower potential under a N atmosphere demonstrated a higher
NRR activity. After a continuous potentiostatic electrolysis at the
constant potentials (Figure 3a), NH +
-contained products were
2
O
3
were
determined to be 14.6 %. The possible reasons for that the sum
of H and NH FEs is less than 100 % are the reduction of catalyst
4
2
3
3+
0
N
2
itself (from Sb to Sb evidenced by comparing XRD before and
after NRR), as well as the capacitance of the carbon support.[23]
Time-depended ICP-AES analysis results (Table S1)
revealed that the concentration of antimony in electrolyte was
0.021 ppm after electrolysis for 6 h and then increased very slowly
over long period, demonstrating the residual amorphous layer
was relatively stable that wrapped the inner Sb0 moiety, which
2
4
carefully detected by indophenol blue method, as shown in Figure
S6b, and the corresponding calibration curves are shown in
Figure S7. No by-product N
Chrisp method (Figure S8), suggesting the good selectivity of
PC/Sb/SbPO for the NRR. As illustrated in Figure 3b, the highest
2 4
H was detectable by the Watt and
0
effectively prevented the Sb from the cathodic corrosion. Even
4
x
so, as more catalyst combined with the NH , as well as the
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Angewandte Chemie International Edition
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COMMUNICATION
−1
negative effect of the higher ammonia concentration on chemical
reaction direction, the activity of the catalyst still gradually
maximum NH
3
yield rate reach to 23 µg h−1 mgcat. at - 0.3 V. As
evidenced by Figure S19a, the NH
3
yield rate of PC/Sb/SbPO
was 13.5 µg h mgcat. at - 0.1 V, which is much higher than those
of the C/Sb/Sb
(2.2 µg h−1 mgcat.−1) and PC (8.6 µg h−1 mgcat.−1),
and suggests a synergistic effect of PC and SbPO resulting in
the high electrocatalytic activity. The durability and stability of
PC/Sb/SbPO toward the NRR were also evaluated by cycling
tests and long-term continuous potentiostatic electrolysis. The
recycling tests were performed at - 0.10 V (vs. RHE) for 1 h. The
chronoamperometry results were shown in Figure S19b. After five
4
−
1
−1
declined. We also compared NRR performance of PC/Sb/SbPO
with those of reported catalysts in an acidic electrolyte, as listed
4
2
O
3
in Table S2. The activity of PC/Sb/SbPO
among the listed catalysts for the NRR.
4
is one of the highest
4
To verify that the detected NH
NRR on PC/Sb/SbPO three control experiments were
performed: ⅰ) using carbon paper without catalyst loading as the
working electrode; ⅱ) continuously feeding N to the testing
apparatus at the open-circuit potential; and ⅲ ) testing the
PC/Sb/SbPO electrode under an Ar gas atmosphere. As
evidenced by the corresponding UV-vis absorption spectra shown
in Figure S13-S17, no NH product was detected under these
conditions, indicating that the NH product is indeed produced by
the NRR on PC/Sb/SbPO
3
was solely generated via the
4
4
,
2
3
parallel tests, the NH formation rate and the corresponding FEs
4
presented only a slight decrease relative to their initial values
(Figure S19c). Continuous potentiostatic electrolysis at - 0.1 V for
24 h did not result in any apparent change in the current density
3
3
of PC/Sb/SbPO
carried out to test that the detected NH
The testing results under different conditions are collected in
4
(Figure S20). The controlled experiments were
4
.
3
was only from the NRR.
Figure S21-25, all these results confirmed that NH
NRR.
3
is from the
The XRD, HRTEM, XPS and XANES measurements were
adopted to monitor the changes of structure and composition of
PC/Sb/SbPO
the components of SbPO
the NRR, ensuring sufficient active sites for the adsorption and
activation of N reduction occurred
molecules,[26] in which the N
and positively charged P in
4
catalyst before and after the NRR testing. Evidently,
4
and PC in the hybrids were active for
2
2
at the active sites of Sb in SbPO
4
carbon substrate.[ The doping of P into carbon effectively tuned
27]
the electronic structure of the hybrid catalyst, resulted in
enhanced conductivity.[28] Meanwhile, the Sb/SbPO
particles
were anchored on the P-doped carbon substrate, preventing
4
aggregation of the Sb/SbPO
4
particles and benefiting high
exposure of active sites during the NRR process,[ which led to
excellent electrochemical durability and structural stability. The
Sb0 species were not served as active sites for directly
29]
Figure 4. a) LSV curves of PC/Sb/SbPO
4
in Ar- and N
with a scan rate of 10 mV s . b) Time-dependent current density curves for
PC/Sb/SbPO at different potentials for 1 h in 0.1 M Na SO . c) UV-Vis
absorption spectra of the electrolytes stained with indophenol indicator after
electrolysis at a series of potentials for 1 h. d) NH yields and FEs for
PC/Sb/SbPO at corresponding potentials.
2 2 4
-saturated 0.1 M Na SO
participating in the NRR due to the surface coverage by SbPO
However, as an effective support, the existence of Sb0 species
significantly increased the exposure of the external SbPO
thereby producing positive effect on the NRR performance.
Although the SbPO moiety went through a partial dissolution into
4
.
-
1
4
2
4
4
,
3
4
4
electrolyte during the NRR process, which was not bringing
significant impact on the electrocatalytic activity and stability of
The electrocatalytic performance of the PC/Sb/SbPO
the NRR in 0.1 M Na SO
solution was also measured.[24] The
NH was determined by spectrophotometry method using salicylic
acid as a color agent.[25] The corresponding calibration curves for
the NH concentration-dependent absorbance are shown in
Figure S18. LSV curves in Figure 4a showed the increased
current density in the N atmosphere compared to that in the Ar-
saturated electrolyte indicated that PC/Sb/SbPO is active for the
NRR. The i-t curves in Figure 4b were recorded at five given
potentials. The corresponding UV-vis absorption spectra of the
electrolytes colored with indophenol indicator after the NRR
testing are shown in Figure 4c. Surprisingly, as shown in Figure
4
toward
PC/Sb/SbPO
In summary, the PC/Sb/SbPO
synthesized via a facile solid-state phosphorization reaction with
C/Sb/Sb as precursor under an Ar flow. Benefiting from the
integrated advantages of the active sites of PC and SbPO , as
well as the conductivity enhanced by PC, the resultant
PC/Sb/SbPO exhibited high activities, excellent FEs and nice
stability for the electrocatalytic N to NH conversion in both acidic
and neutral electrolytes under ambient conditions. A peak FE of
4
toward NH
3
electrosynthesis.
2
4
4
catalyst was successfully
3
2
O
3
3
4
2
4
4
2
3
3
0
1 % was achieved with PC/Sb/SbPO
.15 V (vs. RHE) in 0.1 M HCl electrolyte, as well as 34 % at a
SO solution, both
4
at a lower potential of -
lower potential of - 0.1 V in 0.1 M Na
2
4
4d, the highest FE is up to 34 % at a lower potential of - 0.1 V (vs.
significantly exceeding most of the reported NRR electrocatalysts.
This study provides a new design strategy of coupling different
active species to one advanced structure to enhance the
RHE), to the best of our knowledge, which is the highest value of
FEs among those of all the reported non-noble metal-based
catalysts for the N
2
NRR in neutral electrolyte under mild
2 3
performance of a catalyst for artificial N transformation to NH .
conditions. We compared the NRR performance of our catalyst
with the reported catalysts in neutral conditions in Table S3. The
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Angewandte Chemie International Edition
10.1002/anie.201906521
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Antimony-based composites loading
on phosphorus-doped carbon exhibits
excellent faradaic efficiency for the
conversion of nitrogen to ammonia
under ambient condition in both acidic
and neutral electrolyte. Two active
species including P-doped carbon and
antimony phosphate synergistically
improve nitrogen reduction reaction
performance
Xien Liu,* Haeseong Jang, Ping Li, Jia
Wang, Qing Qin,* Min Gyu Kim,
Guangkai Li, and Jaephil Cho*
Page No. – Page No.
Antimony-Based Composites
Loading on Phosphorus-Doped
Carbon for Boosting Faradaic
Efficiency of the Electrochemical
Nitrogen Reduction Reaction
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