Anodic Hydrazine Oxidation Assists Energy-Efficient Hydrogen Evolution over a Bifunctional Cobalt Perselenide Nanosheet Electrode

Article abstract of DOI:10.1002/anie.201803543

Water electrolysis is a promising source of hydrogen; however, technological challenges remain. Intensive efforts have focused on developing highly efficient and earth-abundant electrocatalysts for water splitting. An effective strategy is proposed, using a bifunctional tubular cobalt perselenide nanosheet electrode, in which the sluggish oxygen evolution reaction is substituted with anodic hydrazine oxidation so as to assist energy-efficient hydrogen production. Specifically, this electrode produces a current density of 10 mA cm^?2 at ?84 mV for hydrogen evolution and ?17 mV for hydrazine oxidation in 1.0 m KOH and 0.5 m hydrazine electrolyte. An ultralow cell voltage of only 164 mV is required to generate a current density of 10 mA cm^?2 for 14 hours of stable water electrolysis.

Full text of DOI:10.1002/anie.201803543

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
International Edition Chemie
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Accepted Article
Title: Substituted Anodic Hydrazine Oxidation Assisting Energy-
efficient Hydrogen Production Based on Bifunctional Cobalt
Perselenide Nanosheet Electrode
Authors: Bao Yu Xia, Jun-Ye Zhang, Hongming Wang, Yifan Tian, Ya
Yan, Qi Xue, Ting He, Hongfang Liu, Chundong Wang, and
Yu Chen
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201803543
Angew. Chem. 10.1002/ange.201803543
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http://dx.doi.org/10.1002/ange.201803543

Angewandte Chemie International Edition
10.1002/anie.201803543
COMMUNICATION
Substituted Anodic Hydrazine Oxidation Assisting Energy-
efficient Hydrogen Production Based on Bifunctional Cobalt
Perselenide Nanosheet Electrode
a
b
c
d
e
a
a
Jun-Ye Zhang, Hongming Wang, Yifan Tian, Ya Yan, Qi Xue, Ting He, Hongfang Liu, Chundong
Wang, * Yu Chen, * and Bao Yu Xia a, f*
c,
e,
Abstract: Water electrolysis is promising source for hydrogen
production yet challenging. Intensive efforts have been riveted on
developing highly efficient and earth-abundant electrocatalysts for
water splitting. In this work, we propose an effective strategy through
replacing sluggish oxygen evolution by the substituted anodic
hydrazine oxidation to assist the energy-efficient hydrogen production
energy sources.[1] Hydrogen energy is well-though-out as one of
the auspicious candidates due to its high caloric value and clean
product.[2] The large-scale hydrogen production with high purity is
therefore of great significance to prompt hydrogen energy
technologies.[3] Compared with steam reforming and coal
gasification, hydrogen production from water splitting by
renewable energy is energy-efficient and eco-friendly for the
reformation of energy system.[4] Generally, water electrolysis can
based on
a bifunctional tubular cobalt perselenide nanosheet
electrode. Specifically, this electrode can afford a current density of
-
2
1
0 mA cm at -84 mV for hydrogen evolution and -17 mV for hydrazine
2
be divided into cathodic hydrogen evolution reaction (HER: 4H O
-
-
oxidation in 1.0 M KOH and 0.5 M hydrazine electrolyte. An ultralow
2
+ 4e → 2H + 4OH ) and anodic oxygen evolution reaction (OER),
cell voltage of only 164 mV is required to afford the current density of
and efficient electrocatalysts for HER and OER is necessary to
reduce the overall voltage of full cell.[5] So far, noble metal based-
-
2
10 mA cm during the 14 hours stable water electrolysis.
x
catalysts (such as Pt and IrO ) have exhibited excellent activities
for electrolysis reactions, but their practical application is still
restricted by the high cost and unsated stability.[6] Continuous
The paradox of increasing energy demand and decreasing fossil
fuel urges the human society to develop the sustainable and clean
efforts have been devoted to developing highly efficient and stable
earth-abundant electrocatalytic composites (such as sulfides,
hydroxides etc.) to prompt the HER and OER.[
7]
[
a]
J Zhang, T He, Dr. Prof. H Liu, Dr. Prof. B. Y. Xia
Key Laboratory of Material Chemistry for Energy Conversion and
Storage (Ministry of Education), Hubei Key Laboratory of Material
Chemistry and Service Failure, School of Chemistry and Chemical
Engineering, Wuhan National Laboratory for Optoelectronics
Huazhong University of Science and Technology (HUST)
Nanotechnology has successfully engineered and advanced
the nanocatalysts design for water splitting.[8] However, even
x
using the best HER catalyst Pt and OER catalyst IrO to drive
water splitting, the overall voltage at 10 mA cm-2 is much higher
than 1.50 V,[9] as the theoretical voltage of water electrolysis is
1037 Luoyu Road, Wuhan 430074, PR China
E-mail: byxia@hust.edu.cn
Dr. Prof. H. Wang
Institute for Advanced Study, Nanchang University, 999 Xuefu
Road, Nanchang, PR China
Y Tian, Dr. C. Wang
mainly determined by the sluggish anodic OER (1.23 V vs.
RHE).[10] In particular, hydrazine, a kind of rocket fuel and
[
b]
c]
aqueous contaminant, could be electrochemically oxidized by
[
transitional-metal catalyst composites (sulfides,[11] phosphides,[12]
School of Optical and Electronic Information, Huazhong University
of Science and Technology (HUST), 1037 Luoyu Road, Wuhan
etc.) at -0.33 V vs. RHE.[13] Inspired by hydrazine fuel cells and
chloro-alkaline industry, the substituted anodic reaction such as
430074, PR China, E-mail: apcdwang@hust.edu.cn
-
-
[
d]
e]
Dr. Prof. Y. Yan
2 4 2 2
hydrazine oxidation (HzOR: N H + 4OH → N + 4H O + 4e ) may
School of Materials Science & Engineering, University of Shanghai
for Science and Technology, 516 Jungong Road, Shanghai 200093,
PR China
be another effective and valuable approach to lower the overall
electrolysis voltages.[14] Therefore, with the assistance of earth-
abundant electrocatalysts, the substituted anodic hydrazine
[
Q Xue, Dr. Prof. Y. Chen
Key Laboratory of Macromolecular Science of Shaanxi Province,
Key Laboratory of Applied Surface and Colloid Chemistry (MOE),
Shaanxi Key Laboratory for Advanced Energy Devices, School of
Materials Science and Engineering, Shaanxi Normal University
oxidation could reduce the cost and overpotential of whole
electrolysis cell,[15] thus realizing the production of pure hydrogen
with lower power implementations. Meanwhile the reaction is
accompanied with other benefit like the degradation of aqueous
hydrazine contaminants to nitrogen and water.[
199 Chang’an Rd, Xi’an 710062, PR China
16]
E-mail: ndchenyu@gmail.com
[f]
Dr. Prof. B. Y. Xia
Shenzhen Insitute of Huazhong University of Science and
Technology, 9 Yuexing Road, Shenzhen 518000, PR China
Herein, we report an effective approach for the electrochemical
production of hydrogen, assisted by the substituted anodic
hydrazine oxidation in water electrolysis, which is based on a
Supporting information for this article is given via a link at the end of
the document.
bifunctional tubular cobalt perselenide (CoSe
electrode. Specifically, the as-fabricated CoSe
2
)
nanosheet
electrode
2
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Angewandte Chemie International Edition
10.1002/anie.201803543
COMMUNICATION
performs a superior catalytic activity and strong durability for HER
and HzOR, which can output a current density of 10 mA cm-2 at -
during the hydrothermal selenization. Such hierarchical
nanosheet structure with interconnected configuration endows an
excellent accessibility of abundant active sites, interfacial contact,
mass transport and gas diffusion for electrochemical reactions
(Figure S3, SI).[18]
84 mV for HER and -17 mV for HzOR respectively. An ultralow
cell voltage of only 164 mV is required to afford the current density
of 10 mA cm-2 during the 14 hours stable water electrolysis, which
is gratifyingly superior than the minimum theoretical voltage of
water splitting (1.23 V). This work provides not only an effective
and earth-abundant electrode for hydrogen evolution, but more
importantly, a low-energy and eco-friendly philosophy to render
electrochemical hydrogen production by substituted anodic
oxidation reaction.
Figure 2. XRD pattern (a) ("*" is ascribed to the signal peaks of nickel substrate),
Raman spectrum (b), Co 2p (c) and Se 3d (d) XPS spectra of CoSe .
2
X-ray diffraction (XRD) pattern shows evident peaks at 30.49°,
4.19°, 37.57°, 43.66°, and 51.70° which are in accord with the
3
faces of (200), (210), (211), (220), and (311), respectively,
indicating the diffraction peaks of CoSe electrode are in well
agreement with the cubic phase (JCPDS: 89-7184) (Figure
a).[19] Raman spectroscopy in Figure 2b signifies a characteristic
2
Figure 1. SEM (a, b) and (HR)TEM images (c-f) of tubular CoSe nanosheets.
Inset of (f) layered structure and model structure of nanosheets.
2
2
-1
The tubular CoSe
2
nanosheets electrode is prepared by a facile
signal peak at 182 cm , which is related to the Se-Se stretching
[
20]
two-step hydrothermal method, the first step is the preparation of
dihydroxycarbonate precursors followed by the subsequent
mode of cubic CoSe
2
.
Moreover, the corresponding energy-
dispersive X-ray (EDX) results illustrate the symmetrical and
homogenous elements distribution (Figure S4, SI). The elemental
content of Co and Se from EDX are 32.82% and 67.18%, which
is consistent with the ICP-OES (Co:Se = 33.65%:66.35%) and X-
ray fluorescence (XRF) analysis (Figure S5, SI), demonstrating
the element ratio of Co and Se to be approximately 1:2. X-ray
photoelectron spectroscopy (XPS) is performed to investigate the
transformation of tubular CoSe
2
nanosheet through the
hydrothermal selenization method (Experimental Section for the
details). Scanning electron microscopy (SEM) image shows the
luxuriant bunch structure grows on the nickel foam substrate
(
Figure 1a), similar to the morphology of previous
dihydroxycarbonate precursor (Figure S1, SI). The as-obtained
tubes have a uniform diameter of ~ 250 nm, which is larger than
the smooth precursor nanofibers (~ 100 nm). There are enormous
number of lace-structured and gauzy nanosheets surrounding on
2
surface chemistry of as-obtained CoSe . The Co 2p spectrum
shows that both peaks of 781.48 eV and 797.24 eV are assigned
to Co(II) 2p3/2 and Co(II) 2p1/2, respectively (Figure 2c). Notably,
there is a pair of peaks at 779.54 eV and 794.49 eV are assigned
to Co(III) 2p3/2 as well as Co(III) 2p1/2, accompanying with two
2
the outer wall surface of tubular CoSe (Figure 1b). Transmission
electron microscopy (TEM) observation in Figure 1c confirms the
tubular structure (Figure S2, SI), and the outer surface composes
of dense interconnected nanosheets (Figure 1d). High-resolution
[
21]
satellite peaks at 784.83 eV and 803.0 eV. There is significant
difference between cobalt precursor and as-obtained CoSe
2
(
(
HR) TEM image further displays that the lattice spacing of the
211), (210) and (200) planes are 0.237, 0.265, and 0.295 nm and
2
samples, indicating that cobalt species in CoSe mainly exists in
high valence (Figure S6a, SI).[ Furthermore, XPS spectrum of
Se 3d reveals that both peaks at 54.9 eV and 55.6 eV are
attributed to Se 3d3/2 and 3d5/2, respectively, which is consistent
22]
the lateral dimension of such a thin nanosheets (number of layers
2~5) is only around 5.0 nm with an interlayer space of 0.67 nm,
=
[
23]
respectively (Figure 1e, 1f). The folded edges of gossamer
nanosheets are clearly observed (Figure 1f), which corresponds
to the different layers of CoSe
with cobalt perselenides reported. A peak at 59.75 eV would be
ascribed to the Se-O bond due to the surface oxygen
[
24]
2
. In particular, some crystalline
adsorption/oxidation (Figure 2d). Moreover, surface oxygen is
further examined by O 1s XPS spectrum as demonstrated by Se-
O bond at 531.47 eV (Figure S7, SI).[25]
distortions are observed as the crystal fringes along the curled
edge are discontinuous, which would result in the rich defects and
open edges (Figure 1f). Moreover, the Se-Co-Se atom structure
is also clearly visible together with the expanded Se-Co-Se band
The electrochemical performance of CoSe
2
electrode for
hydrogen evolution is investigated in 1.0 M KOH solution using
standard three-electrode system (graphite rod as counter
electrode). The overpotentials at a current density of 10 mA cm-2
(
Figure 1f inset).[17] The formation of tubular structured CoSe
nanosheets might involve the ion exchange and diffusion process
2
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Angewandte Chemie International Edition
10.1002/anie.201803543
COMMUNICATION
(
η
10) of cobalt precursor and nickel foam substrate are 193 mV
To guarantee the general function of hydrogen production cell as
proposed, it is also significant to ascertain that the as-composed
CoSe electrode could successfully work in the alkaline electrolyte
2
and 241 mV, respectively (Figure 3a). While the η10 of CoSe
electrode is only 79 mV to achieve a current density of 10 mA cm
2
2
-
.
This is comparable with commercial Pt/C (38 mV) and lower
containing hydrazine. With increasing the hydrazine
concentration, no obvious changes happen in the potential
than those of selenium-based or cobalt-based HER
electrocatalysts reported in alkaline electrolyte (Table S1, SI).
Moreover, Pt/C catalyst shows the smallest Tafel slope value (48
-2
difference at the current density of over 10 mA cm , only a
negative shift for onset-potential is mainly due to the standard
redox potential of hydrazine (Figure 4a). Even in the 1.0 M KOH
-1
mV dec ), owing to its mediocre reaction ΔG (Figure 3b). As
expected, CoSe
2
electrode exhibits a smaller Tafel slope (84 mV
2
with 0.5 M hydrazine solution, the as-obtained CoSe electrode
-1
-1
dec ) compared with cobalt precursor (106 mV dec ) and nickel
still shows an outstanding catalytic activity on hydrogen evolution
which is evidenced by a small η10 of 84 mV, similar to the results
in KOH electrolyte without hydrazine involved (Movie S1, SI).
-1
foam substrate (121 mV dec ), revealing a facile kinetics for
hydrogen generation. Meanwhile, the electrochemical
impendence spectroscopy (EIS) results shows four samples have
a similar ohmic resistance (R ) due to the same Ni foam substrate
Figure S8, SI). However, compared to cobalt precursor and
Additionally, the catalytic capability of CoSe
acknowledged in KOH electrolyte containing various hydrazine
concentrations (Figure 4b). Obviously, CoSe anode generates
2
electrode is further
s
(
2
pristine nickel foam, CoSe
2
electrode has a much smaller charge
negligible current corresponding to its oxidation process in the
absence of hydrazine in the electrolyte. However, the introduction
of hydrazine (0.1 M N H solution) into the electrolyte gives a
2 4
significant current response. Also there is a decrease onset
potential (till -44 mV vs. RHE) and increase in current densities
for HzOR with the increased hydrazine concentration (Figure S13,
SI), approving the effective approach to lower anodic
overpotential by the substituted anodic hydrazine oxidation
transfer resistance (Rct) at the interface of electrocatalyst and
electrolyte, suggesting an excellent interfacial contact and faster
charge transfer between the hierarchical nanosheets structure
and electrolyte. Furthermore, the double-layer capacitance (Cdl
of CoSe
electrode is 4.45 mF cm-2 (Figure S9, SI), which is 50
times higher than that of cobalt precursor electrode (0.08 mF cm-
2)
. This momentous difference suggests that the excellent HER
performance of CoSe electrode is triggered by the increased
)
2
2
reactions. Compared with cobalt precursor, nickel foam and IrO
CoSe electrode demonstrates the excellent activity for the
hydrazine oxidation (Figure S14 and S15, SI), approving that the
2
,
electrochemically active surface area enabled by the hierarchical
nanosheet structure and excellent exposure of massive active
sites to the reactants. Moreover, density functional theory (DFT)
calculation results reveal that Co site is favorable for adsorption
2
presence of CoSe
hydrazine oxidation process (N
proposed in Figure S16.[27] Moreover, CoSe
2
phase is active for HzOR (Movie S2, SI). The
-
H
2 4
+ 4OH → N
2
+ 4H
2
O + 4e) is
of water molecular, while the transformation of Hads to H
2
occurs
2
electrode exhibits
on the active Se sites (Figure S10, SI). Based on above
electrochemical results and DFT calculations, the intrinsic
the comparable, even surpassed activity than Pt/C electrode at
higher potentials for HER in 1.0 M KOH electrolyte containing 0.5
electrocatalytic HER activity of CoSe
2
nanostructures is ascribed
2
M hydrazine (Figure 4c). CoSe electrode achieves anodic current
to the nature of Co sites and the formation of Co-Se bonds
together with the enhanced electric behavior.[26] The outstanding
electrochemical stability of as-prepared electrode is also
demonstrated by the steady whole 50 h durability test (Figure 3c).
The catalytic current remains stable and no dramatic η10 loss after
densities of 10 and 100 mA cm-2 at -17 mV and 170 mV,
respectively, much more negative than that of Pt/C electrode,
which are 51 mV and 280 mV respectively. These results certainly
2
certify the noteworthy role of earth-abundant CoSe nanostructure
as the bifunctional electrode for efficient hydrazine oxidation
assisting-water electrolysis.
50 h test (Figure 3d). Raman and SEM results also suggest the
robust electrode also remains the intact morphology and structure
after this long-term test (Figure S11, S12, SI).
Figure 4. (a) Hydrogen evolution and (b) hydrazine oxidation LSV
polarization curves of CoSe
concentration; (c) LSV polarization curves of CoSe
HER/HzOR couple in 1.0 M KOH with 0.5 M N solution; (d) LSV
polarization curves comparison of CoSe for water electrolysis assisting
with or without hydrazine anodic oxidation; (e) Faradic efficiency of
hydrogen production and (f) Cell stability test based on a CoSe /CoSe
couple at 10 mA cm-2 in 1.0 M KOH with 0.5 M hydrazine solution.
2
in 1.0 M KOH containing different hydrazine
2
and Pt/C for
2 4
H
2
Figure 3. iR-corrected LSV polarization curves (a) and corresponding Tafel
2
2
slopes (b) of CoSe
2
, Pt/C on Ni substrate, nickel foam substrate and cobalt
-
2
precursor. (c) 50 h stability test of CoSe
2
at a current density of 10 mA cm . (d)
LSV curves of before and after 50 h stability test. All the experiments are
implemented in 1.0 M KOH solution.
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Angewandte Chemie International Edition
10.1002/anie.201803543
COMMUNICATION
Afterwards, the combined electrochemical results of CoSe
electrodes for overall water electrolysis in KOH with and without
hydrazine electrolyte are compared (Figure 4d). The comparable
2
Acknowledgements
This work is financial supported by National 1000 Young Talents
Program of China. The National Natural Science Foundation of
China (51702213), the Innovation Foundation of Shenzhen
Government (JCYJ20160408173202143), the Fundamental
Research Funds for the Central University (2017KFXKJC002 and
GK201602002), and the Innovation Research Funds of HUST
HER performance is observed for CoSe
2
electrodes, similar
potentials of -84 mV (with hydrazine) and -90 mV (without
hydrazine) vs. RHE are required to achieve a cathodic current
-2
density 10 mA cm . For the anodic oxidation, CoSe
2
electrode
exhibits an excellent oxygen evolution performance, 1.513 V vs.
RHE to achieve an anodic current density of 10 mA cm . But even
though, the full cell voltage of an assembled cell for water splitting
-2
(
2017KFYXJJ164) are also acknowledged. The authors also
acknowledge the support of the Analytical and Testing Center of
Huazhong University of Science and Technology for XRD, XRF,
ICP-OES, SEM, TEM, Raman, XPS and Nitrogen sorption
measurements.
by CoSe
to afford the considerable current density of 10 mA cm (Figure
S17, SI). However, CoSe electrodes demonstrates an impressive
electrochemical HzOR activity at -17 mV and 170 mV vs. RHE to
2 2
electrodes or Pt║IrO couple may be higher than 1.5 V
-2
2
-2
afford the anodic current density of 10 and 100 mA cm ,
respectively. It endows an ultralow voltage for a complete water
electrolysis assembled by anodic HzOR and cathodic HER. Such
a full cell design reveals that the sluggish anodic oxidation is
mainly responsible for the energy consumption for
electrochemical hydrogen production. Fortunately, the hydrazine
oxidation can replace the cathode water oxidation reaction, and
thus remarkably reduce the full cell voltage and achieve the
energy-saving purpose in water electrolysis technologies.
Keywords: Cobalt perselenide • Bifunctional electrocatalyst •
Hydrogen evolution • Hydrazine oxidation • Water electrolysis
[
1]
(a) S. Chu, A. Majumdar, Nature 2012, 488, 294-303; (b) B. Y. Xia,
Y. Yan, N. Li, H. B. Wu, X. W. D. Lou, X. Wang, Nat Energy 2016,
1, 15006; (c) N. Armaroli, V. Balzani, Angew Chem Int Ed 2007,
46, 52-66.
[
2]
K. K. Sakimoto, A. B. Wong, P. Yang, Science 2016, 351, 74-77.
(a) J. Liu, Y. Liu, N. Liu, Y. Han, X. Zhang, H. Huang, Y. Lifshitz, S.-
T. Lee, J. Zhong, Z. Kang, Science 2015, 347, 970-974; (b) C.
Tang, R. Zhang, W. Lu, L. He, X. Jiang, A. M. Asiri, X. Sun, Adv
Mater 2017, 29, 1602441.
(a) O. Khaselev, J. A. Turner, Science 1998, 280, 425-427; (b) J. A.
Turner, Science 2004, 305, 972-974; (c) X. Wang, K. Maeda, A.
Thomas, K. Takanabe, G. Xin, J. M. Carlsson, K. Domen, M.
Antonietti, Nat Mater 2009, 8, 76.
[3]
[4]
2
Moreover, the cathodic CoSe electrode displays a high hydrogen
production faradic efficiency of 98.3% (Figure 4e), suggesting the
complete electron utilization during the hydrogen production.
Figure 4f shows the potential response of two-electrode
[
5]
(a) Z. W. Seh, J. Kibsgaard, C. F. Dickens, I. Chorkendorff, J. K.
Nørskov, T. F. Jaramillo, Science 2017, 355, eaad4998; (b) Y. T.
Xu, X. Xiao, Z. M. Ye, S. Zhao, R. Shen, C. T. He, J. P. Zhang, Y.
Li, X. M. Chen, J Am Chem Soc 2017, 139, 5285-5288; (c) T. Liu,
L. Xie, J. Yang, R. Kong, G. Du, A. M. Asiri, X. Sun, L. Chen,
ChemElectroChem 2017, 4, 1840-1845.
(a) H. Wang, H.-W. Lee, Y. Deng, Z. Lu, P.-C. Hsu, Y. Liu, D. Lin, Y.
Cui, Nat Commun 2015, 6, 7261; (b) I. Roger, M. A. Shipman, M.
D. Symes, Nat Rev Chem 2017, 1, 0003.
(a) A. J. Esswein, Y. Surendranath, S. Y. Reece, D. G. Nocera,
Energy Environ Sci 2011, 4, 499-504; (b) S. Cobo, J. Heidkamp,
P.-A. Jacques, J. Fize, V. Fourmond, L. Guetaz, B. Jousselme, V.
Ivanova, H. Dau, S. Palacin, Nat Mater 2012, 11, 802; (c) J.
Staszak-Jirkovský, Christos D. Malliakas, Pietro P. Lopes, N.
Danilovic, Subrahmanyam S. Kota, K.-C. Chang, B. Genorio, D.
Strmcnik, Vojislav R. Stamenkovic, M. G. Kanatzidis, N. M.
Markovic, Nat Mater 2015, 15, 197; (d) C. You, Y. Ji, Z. Liu, X.
Xiong, X. Sun, ACS Sustainable Chem Eng 2018, 6, 1527-1531.
X. Xiong, Y. Ji, M. Xie, C. You, L. Yang, Z. Liu, A. M. Asiri, X. Sun,
Electrochem Commun 2018, 86, 161-165.
HER/HzOR electrolyzer utilizing the bifunctional CoSe
2
electrode.
The paired CoSe electrode only requires 0.164 V to generate a
2
current density of 10 mA cm-2 for 14 hours stable hydrogen
production, which is very little value compared to the theoretically
thermodynamical potential of water splitting (1.23 V). Moreover,
vigorous gas bubbles are produced from the both electrodes
when the assembled cell is driven by a commercial 1.5 V AA
battery (Movie S3, SI), demonstrating the promising potential for
future practical application.
[6]
[
7]
In summary, we demonstrate an effective approach for energy-
efficient hydrogen production by a substituted anodic hydrazine
oxidation to replace the sluggish oxygen evolution based on a
bifunctional tubular CoSe
2
nanosheet electrode. In the presence
[
8]
of hydrazine, CoSe electrode exhibits an excellent activity even
2
better than Pt/C electrode, as evidenced by low potentials of -84
mV for HER and -17 mV for HzOR. The assembled HER/HzOR
electrolyzer system merely requires an ultralow voltage of 0.164
V to drive a current density of 10 mA cm-2 for hydrogen generation
during a stable 14h electrolysis operation. This work not only
provides an efficient and robust electrocatalyst for water splitting,
[9]
(a) Y. P. Zhu, T. Y. Ma, M. Jaroniec, S. Z. Qiao, Angew Chem Int
Ed 2017, 56, 1324-1328; (b) S.-H. Yu, C. Gu, S. Hu, X. Zheng, M.-
R. Gao, Y.-R. Zheng, L. Shi, Q. Gao, X. Zheng, W. Chu, Angew
Chem Int Ed 2018, 57, 1-6.
[10]
(a) J. Zhang, Z. Zhao, Z. Xia, L. Dai, Nat Nanotechnol 2015, 10,
444-452; (b) J. Pan, Y. Y. Xu, H. Yang, Z. Dong, H. Liu, B. Y. Xia,
Adv Sci 2018, 5, 1700691; (c) X. Xiong, C. You, Z. Liu, A. M. Asiri,
X. Sun, ACS Sustainable Chem Eng 2018, 6, 2883-2887.
L. Zhou, M. Shao, C. Zhang, J. Zhao, S. He, D. Rao, M. Wei, D. G.
Evans, X. Duan, Adv Mater 2017, 29, 1604080.
C. Tang, R. Zhang, W. Lu, Z. Wang, D. Liu, S. Hao, G. Du, A. M.
Asiri, X. Sun, Angew Chem Int Ed 2017, 56, 842-846.
(a) T. Asset, A. Roy, T. Sakamoto, M. Padilla, I. Matanovic, K.
Artyushkova, A. Serov, F. Maillard, M. Chatenet, K. Asazawa,
Electrochim Acta 2016, 215, 420-426; (b) M. Sun, Z. Lu, L. Luo, Z.
Chang, X. Sun, Nanoscale 2016, 8, 1479-1484.
[
[
[
11]
12]
13]
but also delivers
a philosophy for the energy-saving full
electrolysis cell design by integrating both corresponding anodic
oxidation and cathodic reduction reactions, thus grasps great
potentials in the future energy conversion and storage
technologies, sustainable environmental issues and beyond.
[
14]
(a) M. A. Oturan, J.-J. Aaron, Crit Rev Environ Sci Technol 2014,
44, 2577-2641; (b) Y. Kuang, G. Feng, P. Li, Y. Bi, Y. Li, X. Sun,
Experimental Section
Angew Chem Int Ed 2016, 55, 693-697; (c) J. Huang, S. Zhao, W.
Chen, Y. Zhou, X. Yang, Y. Zhu, C. Li, Nanoscale 2016, 8, 5810-
5
814; (d) G. Feng, Y. Kuang, P. Li, N. Han, M. Sun, G. Zhang, X.
Experimental Details, DFT calculations, SEM, TEM, XPS, Raman and
other electrochemical measurements.
Sun, Adv Sci 2017, 4, 1600179.
(a) B. You, X. Liu, N. Jiang, Y. Sun, J Am Chem Soc 2016, 138,
[15]
13639-13646; (b) G. Yu, H. Wang, X.-B. Li, L. Gao, H.-L. Wu, J.
This article is protected by copyright. All rights reserved.

Angewandte Chemie International Edition
10.1002/anie.201803543
COMMUNICATION
Yang, L. Cai, T.-B. Ma, C.-H. Tung, L.-Z. Wu, Angew Chem Int Ed
Chem 2016, 128, 5363-5367.
2
017, 57, 192-197.
[22]
[23]
P. Rasiyah, A. Tseung, D. Hibbert, J Electrochem Soc 1982, 129,
1724-1727.
[
[
16]
17]
(a) K. V. Manukyan, A. Cross, S. Rouvimov, J. Miller, A. S.
Mukasyan, E. E. Wolf, Appl Catal A 2014, 476, 47-53; (b) B. You,
N. Jiang, X. Liu, Y. Sun, Angew Chem Int Ed 2016, 55, 9913-9917.
L. Liang, H. Cheng, F. Lei, J. Han, S. Gao, C. Wang, Y. Sun, S.
Qamar, S. Wei, Y. Xie, Angew Chem Int Ed 2015, 54, 12004-
(a) D. Kong, H. Wang, Z. Lu, Y. Cui, J Am Chem Soc 2014, 136,
4897-4900; (b) Y. Guo, C. Shang, E. Wang, J Mater Chem A 2017,
5, 2504-2507.
W. Zhou, J. Lu, K. Zhou, L. Yang, Y. Ke, Z. Tang, S. Chen, Nano
Energy 2016, 28, 143-150.
C. Xia, Q. Jiang, C. Zhao, M. N. Hedhili, H. N. Alshareef, Adv
Mater 2016, 28, 77-85.
P. Chen, K. Xu, S. Tao, T. Zhou, Y. Tong, H. Ding, L. Zhang, W.
Chu, C. Wu, Y. Xie, Adv Mater 2016, 28, 7527-7532.
Y. Meng, X. Zou, X. Huang, A. Goswami, Z. Liu, T. Asefa, Adv
Mater 2014, 26, 6510-6516.
[24]
[25]
[26]
[27]
1
2008.
B. You, Y. Sun, Acc Chem Res 2018, DOI:
0.1021/acs.accounts.8b00002.
[
[
18]
19]
1
Y. Liu, H. Cheng, M. Lyu, S. Fan, Q. Liu, W. Zhang, Y. Zhi, C.
Wang, C. Xiao, S. Wei, B. Ye, Y. Xie, J Am Chem Soc 2014, 136,
15670-15675.
[
[
20]
21]
E. Anastassakis, Solid State Commun 1973, 13, 1297-1301.
L. Xu, Q. Jiang, Z. Xiao, X. Li, J. Huo, S. Wang, L. Dai, Angew
This article is protected by copyright. All rights reserved.

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COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
a
b
Sweet Synergy of Reaction and
Catalyst: An effective philosophy of
replacing sluggish oxygen evolution
by anodic hydrazine oxidation is
developed for energy-saving water
electrolysis based on a low-cost and
bifunctional cobalt perselenide
electrode.
Jun-Ye Zhang, Hongming Wang, Yifan
c
d
e
a
Tian, Ya Yan, Qi Xue, Ting He,
a
c
Hongfang Liu, Chundong Wang, Yu
Chen, * and Bao Yu Xia a, f*
e,
Page No. – Page No.
Substituted Anodic Hydrazine
Oxidation Assisting Energy-efficient
Hydrogen Production Based on
Bifunctional Cobalt Perselenide
Nanosheet Electrode
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