Efficient Hydrogen Evolution Electrocatalysis at Alkaline pH by Interface Engineering of Ni2P-CeO2

Article abstract of DOI:10.1021/acs.inorgchem.7b02665

It is of significant importance to develop effective non-noble-metal catalysts for hydrogen evolution electrocatalysis under basic conditions. In this study, we demonstrate the facile construction of a Ni₂P-CeO₂ interface based on the central point that low-temperature phosphidation of the NiO-CeO₂ precursor only converts NiO into Ni₂P selectively. The resulting Ni₂P-CeO₂ nanosheet array on Ti mesh behaves as a durable catalyst for alkaline hydrogen evolution reaction (HER) electrocatalysis, and it can reach 20 mA cm^-2 at an overpotential of 84 mV in 1.0 M KOH, outperforming all reported Ni phosphide HER catalysts. Density functional theory calculations reveal that the Ni₂P-CeO₂ interface can promote water dissociation and optimize hydrogen adsorption free energy.

Full text of DOI:10.1021/acs.inorgchem.7b02665

Communication
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Efficient Hydrogen Evolution Electrocatalysis at Alkaline pH by
Interface Engineering of Ni P−CeO
2
2
Ling Zhang, Xiang Ren, Xiaodong Guo, Zhiang Liu, Abdullah M. Asiri, Baihai Li,*,⊥
†
†
‡
§
∥
,#
,†
Liang Chen,* and Xuping Sun*
†
College of Chemistry, Sichuan University, Chengdu 610064, China
‡
§
∥
College of Chemical Engineering, Sichuan University, Chengdu 610065, China
College of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
Chemistry Department, King Abdulaziz University, Jeddah 21589, Saudi Arabia
⊥
School of Energy Science and Engineering, University of Electronic Science and Technology of China, Chengdu, China
#
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
S Supporting Information
*
engineering interface of metal and (hydroxide)oxide as these
ABSTRACT: It is of significant importance to develop
effective non-noble-metal catalysts for hydrogen evolution
electrocatalysis under basic conditions. In this study, we
(
hydroxides)oxides can provide the active sites for dissociation
12,32−38
of water.
Motivated by the above results, we expect that
promoting water dissociation and tuning hydrogen adsorption
demonstrate the facile construction of a Ni P−CeO
2
2
free energy (ΔG ) to a moderate value on Ni phosphides by
H*
interface based on the central point that low-temperature
phosphidation of the NiO−CeO precursor only converts
interface engineering would be promising to develop high-
performance HER electrocatalysts under alkaline conditions,
which, however, still remains challenging.
2
NiO into Ni P selectively. The resulting Ni P−CeO
2
2
2
nanosheet array on Ti mesh behaves as a durable catalyst
Herein, we demonstrate the facile synthesis of a Ni P−CeO
2
2
for alkaline hydrogen evolution reaction (HER) electro-
nanosheet array on Ti mesh (Ni P−CeO /TM). The central
catalysis, and it can reach 20 mA cm−2 at an overpotential
2
2
point in constructing the Ni P−CeO interface lies in the fact
2
2
of 84 mV in 1.0 M KOH, outperforming all reported Ni
phosphide HER catalysts. Density functional theory
calculations reveal that the Ni P−CeO interface can
that low-temperature phosphidation of NiO−CeO only
2
converts NiO into Ni P selectively. The resulting Ni P−
2
2
2
2
−2
CeO /TM can generate 20 mA cm at an η of 84 mV in 1.0
2
promote water dissociation and optimize hydrogen
adsorption free energy.
M KOH, rivaling the performance of all reported Ni phosphide
HER catalysts. This Ni P−CeO also demonstrtes outstanding
2
2
long-term stability. Theory investigation shows that water
dissociation is greatly promoted and ΔG sharply decreases.
H*
ydrogen has been regarded as an attractive alternative
energy source to the diminishing fossil fuels with merits of
Ni P−CeO /TM was obtained via a low-temperature
2
2
H
phosphidation reaction using NiO−CeO /TM as the precursor
2
high efficiency, environmental benignity, and sustainable
(
Figure S1). Powder X-ray diffraction (XRD) patterns for NiO-
1
−9
features.
Alkaline water electrolysis has been regarded as an
CeO (Figure S2) and Ni P−CeO (Figure 1a) demonstrate
2
2
2
appealing and CO -free route to produce pure hydrogen but
2
that NiO (JCPDS No. 47-1049) is converted to Ni P (JCPDS
2
requires efficient hydrogen evolution reaction (HER) electro-
No. 74-1385) while CeO (JCPDS No. 81-0792) remains
10−13
2
catalysts to decrease the overpotential (η) requirement.
unchanged. Scanning electron microscope (SEM) images of
Despite Pt exhibiting the highest catalytic activity, scarcity and
high cost limit its widespreasd applications. Therefore,
developing low-cost and high-efficiency HER elctrocatalysts
free of noble metals is extremely critical.
NiO−CeO /TM (Figure 1b) indicate that the TM substrate is
2
completely covered with a nanosheet array, and the resulting
Ni P−CeO (Figure 1c) still preserves nanoarray features. The
2
2
high-resolution transmission electron microscopy (HRTEM)
Ni, as a non-noble metal, has received much attention due to
its remarkable catalytic activity toward HER, and a considerable
amount of research has concentrated on making Ni-based HER
image (Figure 1d) obtained from a single Ni P−CeO
2
2
nanosheet (Figure S3) discloses the lattice fringes with distances
of 0.31 and 0.16 nm, indexed to (111) and (311) facets of CeO2,
respectively, as well as 0.22 and 0.19 nm in good agree with
spacings of Ni P(111) and Ni P(210) planes, respectively. The
14
catalysts under alkaline conditions, including oxides, phos-
1
5−22
23−28
29,30
phides,
chalcogenides,
nitrides,
etc. Ni phos-
2
2
phides with good electrical conductivity show active catalytic
activity for HER while their alkaline HER performance still
energy dispersive X-ray (EDX) spectrum (Figure S4) and
corresponding elemental mapping images (Figure S5) confirm
the presence of Ni, Ce, P, and O in the product. The electron
31
needs to be further enhanced for applications. In alkaline
media, the generation of hydrogen (H*) intermediates (Volmer
step) is difficult for HER due to the additional need of water
3
2,33
dissociation.
Recent research has demonstrated that the
Received: October 17, 2017
alkaline HER performance of metal can be promoted by the
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.7b02665
����� ����� XXXX, XXX, XXX−XXX
�

Inorganic Chemistry
Communication
Ni P−CeO , two peaks at 129.6 and 130.5 eV reflect the BEs of
2
2
40
P 2p and P 2p , respectively. The peak of P 2p shifts to
3
/2
1/2
3/2
lower BE, while the peak of P 2p1/2 shifts to a higher BE
compared with those of Ni P, which are in good agreement with
2
18
the previous report. The above XPS data suggest charge
41,42
redistribution at the interface,
which may promote HER
catalysis. In Figure 2d, The peaks at 529.5 and 531.6 eV of
2
−
−
Ni P−CeO are attributed to the O in CeO and OH in the
2
2
2
12,38
absorbed water, respectively.
The peak at 531.6 eV of Ni P−
CeO is higher than that of Ni P, indicating that the hybrid
2
2
2
structure of Ni P−CeO can greatly enhance the ability of water
2
2
12
adsorption.
The electrocatalytic HER activity of Ni P−CeO /TM
2
2
−
2
(
Ni P−CeO loading: 1.58 mg cm ) was evaluated in 1.0 M
KOH. Bare TM, Ni P/TM, CeO /TM, and Pt/C loaded on TM
2
2
2
2
with approximately identical loading were also investigated for
comparison. As observed, TM and CeO /TM have negligible
2
−
2
HER activity, while Ni P/TM is active for HER (η
=
2
20‑mA‑cm
1
31 mV). In contrast, Ni P−CeO /TM shows much superior
HER activity and just requires a lower η of 84 mV to reach 20
mA cm . This performance is better than those of all reported
Ni phosphide catalysts under alkaline conditions (Table S2).
The Tafel slope of Ni P−CeO /TM (87 mV dec ) is smaller
than that of Ni P/TM (113 mV dec ; Figure 3b), suggesting
2
2
Figure 1. (a) XRD pattern for Ni P−CeO . SEM images for (b) NiO-
2
2
CeO /TM and (c) Ni P−CeO /TM. (d) HRTEM image of Ni P−
2
2
2
2
−
2
CeO .
2
−1
energy loss spectroscopy mapping images (Figure S6) further
confirm homogeneous distribution of Ni, P, O, and Ce in the
array. Inductively coupled plasma atomic emission spectrometry
2
2
−
1
2
that the Volmer step of HER on Ni P−CeO /TM is faster than
2
2
11
that on Ni P/TM.
(
ICP-AES) analysis (Table S1) determines the atomic ratio of
2
Ni, P, O, and Ce as 0.20:0.09:0.66:0.05.
Figure 2a shows the X-ray photoelectron spectroscopy (XPS)
spectra in the Ni 2p regions for Ni P and Ni P−CeO . The Ni
2
2
2
Figure 3. (a) Polarization curves for HER on Pt/C loaded on TM,
Ni P−CeO /TM, Ni P/TM, CeO /TM, and bare TM. (b) Tafel plots
2
2
2
2
of Pt/C on TM, Ni P−CeO /TM, and Ni P/TM. (c) LSV curves for
2
2
2
Ni P−CeO /TM recorded before and after 1000 cycles. (d)
2
2
Chronopotentiometric and chronoamperometric curves of Ni P−
2
−
2
CeO /TM at a fixed current density of 170 mA cm and η of 180 mV
2
Figure 2. XPS spectra in the (a) Ni 2p, (b) Ce 3d, (c) P 2p, and (d) O
s regions.
for 24 h. All the measurements were performed in 1.0 M KOH.
1
Figure S7 displays a multicurrent-step curve for Ni P−CeO /
2
2
2
p1/2 and Ni 2p3/2 peaks of Ni P−CeO both shift to lower
TM with cathodic current density increasing from 40 to 400 mA
2
2
−
2
binding energies (BEs; 870.6 and 853.3 eV) relative to those of
Ni P (870.9 and 853.6 eV). The other two peaks are shakeup
satellites (identified as “Sat.”). In Figure 2b, the two multiplets
cm . The rapid potential responses indicate the excellent
15
conductivity, mass transportation, and mechanical robustness of
2
15
43,44
Ni P−CeO /TM.
Electrochemical impedance spectrosco-
2
2
(
3
u and v) of the Ce 3d spectrum of Ni P−CeO correspond to
py data (Figure S8) reveal that the Ni P−CeO /TM has a
slightly larger semicircle radius in comparison with that of Ni P/
2
2
2
2
d
and 3d , respectively. The peak marked as v suggests the
5
/2
3/2
1
2
3
+
4+ 39
presence of Ce , while others are in accordance with Ce ,
TM. Durability is an important criterion for evaluation of an
suggesting the coexistence of Ce3 and Ce in the sample. The
peaks of Ce 3d shift to higher BEs compared with those of CeO2.
The XPS spectra of P 2p regions are shown in Figure 2c. For
+
4+
electrocatalyst. Therefore, we recorded the LSV curves of Ni P−
2
CeO /TM before and after cyclic voltammetry scanning at a
2
potential ranging from −0.8 to −1.2 V vs Hg/HgO. The LSV
B
DOI: 10.1021/acs.inorgchem.7b02665
����� ����� XXXX, XXX, XXX−XXX
�

Inorganic Chemistry
Communication
curves before and after 1000 cycles are almost the same (Figure
H ) is identified as the favorable binding site, yielding a ΔG of
N
H*
3
c), suggesting superior stability of Ni P−CeO /TM. Bulk
0.14 eV. Interestingly, the H atom can also reside on the top of P
2
2
electrolysis measurements suggest that Ni P−CeO /TM can
atoms, yielding a similar ΔG value of 0.14 eV. The interaction
2
2
H*
keep stable during strong long-term electrochemical tests
Figure 3d). The SEM observation (Figure S9) reveals that
morphology of Ni P−CeO after the stability test is well kept,
between H and the Ni P−CeO (111) interface would be
2
2
(
significantly enhanced, mainly due to the charge redistribution
at the interface. Similarly, the hollow sites (denoted as HNC
)
2
2
and XRD analysis confirms that it is still Ni P−CeO in nature
above the adjacent Ni atoms of the Ni P−CeO (111) interface
2
2
2
2
(
Figure S10). The Ni P−CeO /TM has a Faradaic efficiency of
are also identified as the most favorable binding sites. The
2
2
nearly 97.8% for the electrochemical hydrogen production
corresponding ΔG shifts to a more desirable value of −0.05
H*
4
5
(Figure S11). Turnover frequency (TOF) was employed to
eV. Actually, the reinforced binding strength of H* on the
Ni P−CeO (111) interface plays a critical role in both the lower
compare the intrinsic activities of Ni P−CeO and Ni2P
2
2
2
2
catalysts. We quantified the active sites by electrochemical
activation barrier for water dissociation and more thermal-
neutral free energy.
active surface area (Figure S12; see SI for calculation details),
46
which is estimated by double-layer capacitance. Figure S13
To sum up, we have successfully proposed interface
shows TOF plots. At an η of 100 mV, Ni P−CeO /TM achieves
engineering of Ni P−CeO as an effective strategy to enhance
2
2
2
2
a higher TOF of 0.593 s− than that of Ni P/TM (0.501 s ),
1
−1
the catalytic hydrogen evolution activity of Ni P in alkaline
2
2
implying its intrinsic superior HER activity. The HER activities
media. The Ni P−CeO nanosheet array is highly durable with
2
2
−
2
of Ni P−CeO /TM under acidic and neutral conditions were
the need of an overpotential of 84 mV to achieve 20 mA cm in
1.0 M KOH. Computing results point out that the superior
activity is attributed to the promoted water dissociation and
optimized free energy of hydrogen adsorption. We believe our
work here not only provides us an appealing catalyst toward
energy-efficient electrochemical hydrogen production but
demonstrates the effective strategy of constructing the transition
metal phosphide/oxide interface for catalytic and other
applications.
2
2
also measured. Ni P−CeO /TM exhibits a small η of 65 and 144
2
2
−2
mV at 20 mA cm in 0.5 M H SO (Figure S14a) and 1.0 M
2
4
PBS (pH = 7.0; Figure S14b), respectively. Notably, Ni P−
2
CeO /TM also shows strong long-term electrochemical
2
durability in 0.5 M H SO (Figure S15a) and 1.0 M PBS
2
4
(
Figure S15b).
It is well-known that the HER activity of the catalyst under
alkaline conditions is determined by water dissociation and the
32−34
adsorption and combination of hydrogen intermediates.
We employed density functional theory (DFT) calculations to
ASSOCIATED CONTENT
■
investigate the involved key reaction steps on the Ni P(111)
2
*
S
Supporting Information
surface (Figure 4a) and Ni P−CeO (111) interface (Figure 4b)
2
2
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.7b02665.
Experimental details, schematic diagram; XRD pattern,
TEM image, EDX spectrum, EDX elemental mapping
images, electron energy loss spectroscopy mapping, Table
S1, multistep chronopotentiometric curve, Nyquist plots,
SEM image, FE data, cyclic voltammograms, plots of TOF
vs overpotential, LSV curves, and time-dependent current
density curves (PDF)
Figure 4. Top-view of (a) Ni P(111) surface and (b) Ni P−
2
2
AUTHOR INFORMATION
CeO (111) interfaces (blue, pink, white, red, and yellow balls represent
2
■
*
*
*
Ni, P, H, O, and Ce atoms, respectively). (c) DFT calculated the
Corresponding Authors
reaction energy diagram of water dissociation on Ni P(111) (orange
2
E-mail: libaihai@uestc.edu.cn.
E-mail: chenliang@nimte.ac.cn.
E-mail: sunxp_scu@hotmail.com.
line) and Ni P−CeO (111) (blue line).
2
2
in order to unravel the intrinsic mechanism for Ni P−CeO with
2
2
ORCID
enhanced electrocatalytic HER activity. First, we calculated the
Abdullah M. Asiri: 0000-0001-7905-3209
Baihai Li: 0000-0002-9266-1791
Liang Chen: 0000-0002-0667-540X
Xuping Sun: 0000-0001-5034-1135
energy profile for water dissociation on the Ni P(111) surface
2
and Ni P−CeO (111) interface. As shown in Figure 4c, a high
2
2
activation energy of 1.18 eV is required to break the O−H bond
of water molecules on the Ni P(111) surface. Interestingly, on
2
the Ni P−CeO (111) interface, the energy barrier is signifi-
2
2
Notes
cantly reduced to be 0.73 eV. The result clearly indicates that the
The authors declare no competing financial interest.
Ni P−CeO (111) interface can facilitate the dissociation of
2
2
water molecules and thus improve the formation of H*
ACKNOWLEDGMENTS
intermediates. In the subsequent combination of H* to H , a
■
2
balance between the rate of proton reduction and the ease of
removal of adsorbed hydrogen from the surface is desired,
This work was supported by the National Natural Science
Foundation of China (No. 21575137). We also appreciate Hui
Wang from the Analytical & Testing Center of Sichuan
University for her help with SEM characterization.
4
7
corresponding to a ΔG value of 0 eV. On the Ni P(111)
H*
2
surface, the hollow site above the adjacent Ni atoms (denoted as
C
DOI: 10.1021/acs.inorgchem.7b02665
����� ����� XXXX, XXX, XXX−XXX
�

Inorganic Chemistry
Communication
Films and Their Use as a Non-Noble Bifunctional Electrocatalyst for
REFERENCES
■
Full Water Splitting. Angew. Chem., Int. Ed. 2015, 54, 12361−12365.
(
1) Zheng, Y.; Jiao, Y.; Jaroniec, M.; Qiao, S.-Z. Advancing the
Electrochemistry of the Hydrogen-Evolution Reaction through
Combining Experiment and Theory. Angew. Chem., Int. Ed. 2015, 54,
2−65.
2) Crabtree, G. W.; Dresselhaus, M. S.; Buchanan, M. V. The
Hydrogen Economy. Phys. Today 2004, 57, 39−44.
3) Pu, Z.; Amiinu, I. S.; Kou, Z.; Li, W.; Mu, S. RuP -Based Catalysts
with Platinum-Like Activity and Higher Durability for the Hydrogen
Evolution Reaction at All pH Values. Angew. Chem., Int. Ed. 2017, 56,
(20) Feng, L.; Vrubel, H.; Bensimon, M.; Hu, X. Easily-Prepared
Dinickel Phosphide (Ni P) Nanoparticles as an Efficient and Robust
2
Electrocatalyst for Hydrogen Evolution. Phys. Chem. Chem. Phys. 2014,
5
(
1
(
6, 5917−5921.
21) Han, A.; Jin, S.; Chen, H.; Ji, H.; Sun, Z.; Du, P. A Robust
Hydrogen Evolution Catalyst Based on Crystalline Nickel Phosphide
Nanoflakes on Three-Dimensional Graphene/Nickel Foam: High
Performance for Electrocatalytic Hydrogen Production from pH 0−14.
J. Mater. Chem. A 2015, 3, 1941−1946.
(
2
1
(
1559−11564.
(22) Laursen, A. B.; Patraju, K. R.; Whitaker, M. J.; Retuerto, M.;
4) Pu, Z.; Amiinu, I. S.; Zhang, C.; Wang, M.; Kou, Z.; Mu, S. Phytic
Sarkar, T.; Yao, N.; Ramanujachary, K. V.; Greenblatt, M.; Dismukes,
G. C. Nanocrystalline Ni P : A Hydrogen Evolution Electrocatalyst of
Acid-Derivative Transition Metal Phosphides Encapsulated in N,P-
Codoped Carbon: An Efficient and Durable Hydrogen Evolution
Electrocatalyst in a Wide pH Range. Nanoscale 2017, 9, 3555−3560.
5
4
Exceptional Efficiency in Both Alkaline and Acidic Media. Energy
Environ. Sci. 2015, 8, 1027−1034.
(
5) Pan, Y.; Hu, W.; Liu, D.; Liu, Y.; Liu, C. Carbon Nanotubes
(23) Zhu, W.; Yue, X.; Zhang, W.; Yu, S.; Zhang, Y.; Wang, J.; Wang, J.
Decorated with Nickel Phosphide Nanoparticles as Efficient Nano-
hybrid Electrocatalysts for the Hydrogen Evolution Reaction. J. Mater.
Chem. A 2015, 3, 13087−13094.
Nickel Sulfide Microsphere Film on Ni Foam as an Efficient
Bifunctional Electrocatalyst for Overall Water Splitting. Chem.
Commun. 2016, 52, 1486−1489.
(
6) Pan, Y.; Chen, Y.; Lin, Y.; Cui, P.; Sun, K.; Liu, Y.; Liu, C. Cobalt
(
24) Tang, C.; Pu, Z.; Liu, Q.; Asiri, A. M.; Sun, X. NiS Nanosheets
2
Nickel Phosphide Nanoparticles Decorated Carbon Nanotubes as
Advanced Hybrid Catalysts for Hydrogen Evolution. J. Mater. Chem. A
016, 4, 14675−14686.
7) Pan, Y.; Liu, Y.; Lin, Y.; Liu, C. Metal Doping Effect of the M-
Co P: Nitrogen-Doped Carbon Nanotubes (M = Fe, Ni, Cu)
Hydrogen Evolution Hybrid Catalysts. ACS Appl. Mater. Interfaces
016, 8, 13890−13901.
8) Pan, Y.; Lin, Y.; Chen, Y.; Liu, Y.; Liu, C. Cobalt Phosphide-Based
Electrocatalysts: Synthesis and Phase Catalytic Activity Comparison for
Hydrogen Evolution. J. Mater. Chem. A 2016, 4, 4745−4754.
9) Pan, Y.; Lin, Y.; Liu, Y.; Liu, C. A Novel CoP/MoS -CNTs Hybrid
Catalyst with Pt-Like Activity for Hydrogen Evolution. Catal. Sci.
Technol. 2016, 6, 1611−1615.
10) Zeng, K.; Zhang, D. Recent Progress in Alkaline Water
Electrolysis for Hydrogen Production and Applications. Prog. Energy
Combust. Sci. 2010, 36, 307−326.
11) Wang, J.; Liu, Q.; Cui, W.; Xing, Z.; Asiri, A. M.; Sun, X. Recent
Progress in Cobalt-Based Heterogeneous Catalysts for Electrochemical
Water Splitting. Adv. Mater. 2016, 28, 215−230.
12) Feng, J.-X.; Xu, H.; Dong, Y.-T.; Lu, X.-F.; Tong, Y.-X.; Li, G.-R.
Efficient Hydrogen Evolution Electrocatalysis Using Cobalt Nanotubes
Decorated with Titanium Dioxide Nanodots. Angew. Chem., Int. Ed.
017, 56, 2960−2964.
13) Lu, W.; Liu, T.; Xie, L.; Tang, C.; Liu, D.; Hao, S.; Qu, F.; Du, G.;
Ma, Y.; Asiri, A. M.; Sun, X. In-Situ Derived Co-B Nanoarray: A High-
Efficiency and Durable 3D Bifunctional Electrocatalyst for Overall
Alkaline Water Splitting. Small 2017, 13, 1700805.
Array Grown on Carbon Cloth as an Efficient 3D Hydrogen Evolution
Cathode. Electrochim. Acta 2015, 153, 508−514.
2
(
(25) Jiang, N.; Tang, Q.; Sheng, M.; You, B.; Jiang, D.; Sun, Y. Nickel
Sulfides for Electrocatalytic Hydrogen Evolution under Alkaline
Conditions: A Case Study of Crystalline NiS, NiS , and Ni S
3 2
2
2
Nanoparticles. Catal. Sci. Technol. 2016, 6, 1077−1084.
2
(
(26) An, T.; Wang, Y.; Tang, J.; Wei, W.; Cui, X.; Alenizi, A. M.;
Zhang, L.; Zheng, G. Interlaced NiS −MoS Nanoflake-Nanowires as
2
2
Efficient Hydrogen Evolution Electrocatalysts in Basic Solutions. J.
Mater. Chem. A 2016, 4, 13439−13443.
(
2
(27) Zhang, J.; Wang, T.; Pohl, D.; Rellinghaus, B.; Dong, R.; Liu, S.;
Zhuang, X.; Feng, X. Interface Eengineering of MoS /Ni S
3 2
2
Heterostructures for Highly Enhanced Electrochemical Overall-
(
Water-Splitting Activity. Angew. Chem., Int. Ed. 2016, 55, 6702−6707.
(28) Tang, C.; Cheng, N.; Pu, Z.; Xing, W.; Sun, X. NiSe Nanowire
Film Supported on Nickel Foam: An Efficient and Stable 3D
Bifunctional Electrode for Full Water Splitting. Angew. Chem., Int. Ed.
(
2
(
015, 54, 9351−9355.
29) Liu, Q.; Xie, L.; Qu, F.; Liu, Z.; Du, G.; Asiri, A. M.; Sun, X. A
(
Porous Ni N Nanosheet Array as a High-Performance Non-Noble-
3
Metal Catalyst for Urea-Assisted Electrochemical Hydrogen Produc-
tion. Inorg. Chem. Front. 2017, 4, 1120−1124.
2
(
(30) Shalom, M.; Ressnig, D.; Yang, X.; Clavel, G.; Fellinger, T. P.;
Antonietti, M. Nickel Nitride as an Efficient Electrocatalyst for Water
Splitting. J. Mater. Chem. A 2015, 3, 8171−8177.
(31) Zhang, Y.; Liu, Y.; Ma, M.; Ren, X.; Liu, Z.; Du, G.; Asiri, A. M.;
Sun, X. A Mn-Doped Ni P Nanosheet Array: An Efficient and Durable
2
(
14) Gong, M.; Zhou, W.; Tsai, M.-C.; Zhou, J.; Guan, M.; Lin, M.-C.;
Hydrogen Evolution Reaction Electrocatalyst in Alkaline Media. Chem.
Commun. 2017, 53, 11048−11051.
(32) Danilovic, N.; Subbaraman, R.; Strmcnik, D.; Chang, K.-C.;
Paulikas, A. P.; Stamenkovic, V. R.; Markovic, N. M. Enhancing the
Alkaline Hydrogen Evolution Reaction Activity through the Bifunc-
Zhang, B.; Hu, Y.; Wang, D.-Y.; Yang, J.; Pennycook, S. J.; Hwang, B.-J.;
Dai, H. Nanoscale Nickel Oxide/Nickel Heterostructures for Active
Hydrogen Evolution Electrocatalysis. Nat. Commun. 2014, 5, 4695.
15) Tang, C.; Zhang, R.; Lu, W.; Wang, Z.; Liu, D.; Hao, S.; Du, G.;
Asiri, A. M.; Sun, X. Energy-Saving Electrolytic Hydrogen Generation:
Ni P Nanoarray as a High-Performance Non-Noble-Metal Electro-
catalyst. Angew. Chem., Int. Ed. 2017, 56, 842−846.
16) You, B.; Jiang, N.; Sheng, M.; Bhushan, M. W.; Sun, Y.
Hierarchically Porous Urchin-Like Ni P Superstructures Supported on
Nickel Foam as Efficient Bifunctional Electrocatalysts for Overall Water
Splitting. ACS Catal. 2016, 6, 714−721.
17) Stern, L.-A.; Feng, L.; Song, F.; Hu, X. Ni P as a Janus Catalyst for
Water Splitting: The Oxygen Evolution Activity of Ni P Nanoparticles.
Energy Environ. Sci. 2015, 8, 2347−2351.
18) Wang, A.-L.; Lin, J.; Xu, H.; Tong, Y.-X.; Li, G.-R. Ni P-CoP
(
tionality of Ni(OH) /Metal Catalysts. Angew. Chem., Int. Ed. 2012, 51,
2
2
12495−12498.
(33) Subbaraman, R.; Tripkovic, D.; Strmcnik, D.; Chang, K.-C.;
Uchimura, M.; Paulikas, A. P.; Stamenkovic, V.; Markovic, N. M.
(
2
Enhancing Hydrogen Evolution Activity in Water Splitting by Tailoring
+
Li -Ni(OH) -Pt Interfaces. Science 2011, 334, 1256−1260.
2
(34) Weng, Z.; Liu, W.; Yin, L.-C.; Fang, R.; Li, M.; Altman, E. I.; Fan,
Q.; Li, F.; Cheng, H.-M.; Wang, H. Metal Oxide Interface
Nanostructures Generated by Surface Segregation for Electrocatalysis.
Nano Lett. 2015, 15, 7704−7710.
(
2
2
(
(35) Jin, H.; Wang, J.; Su, D.; Wei, Z.; Pang, Z.; Wang, Y. In Situ
Cobalt-Cobalt Oxide/N-doped Carbon Hybrids as Superior Bifunc-
tional Electrocatalysts for Hydrogen and Oxygen Evolution. J. Am.
Chem. Soc. 2015, 137, 2688−2694.
(36) Zhang, J.; Wang, T.; Liu, P.; Liao, Z.; Zhuang, S.; Chen, M.;
Zschech, E.; Feng, X.; Liu, Z. Efficient Hydrogen Production on MoNi4
2
Hybrid Nanosheet Arrays Supported on Carbon Cloth as an Efficient
Flexible Cathode for Hydrogen Evolution. J. Mater. Chem. A 2016, 4,
6992−16999.
19) Ledendecker, M.; Krick Calderon, S.; Papp, C.; Steinruck, H.-P.;
Antonietti, M.; Shalom, M. The Synthesis of Nanostructured Ni5P4
1
(
D
DOI: 10.1021/acs.inorgchem.7b02665
����� ����� XXXX, XXX, XXX−XXX
�

Inorganic Chemistry
Communication
Electrocatalysts with Fast Water Dissociation Kinetics. Nat. Commun.
2
(
017, 8, 15437.
37) Subbaraman, R.; Tripkovic, D.; Chang, K.-C.; Strmcnik, D.;
Paulikas, A. P.; Hirunsit, P.; Chan, M.; Greeley, J.; Stamenkovic, V.;
Markovic, N. M. Trends in Activity for the Water Electrolyser Reactions
on 3D M(Ni,Co,Fe,Mn) Hydr(Oxy)oxide Catalysts. Nat. Mater. 2012,
1
(
1, 550−557.
38) Yan, X.; Tian, L.; Chen, X.; He, M. Three-Dimensional
Crystalline/Amorphous Co/Co O Core/Shell Nanosheets as Efficient
3
4
Electrocatalysts for the Hydrogen Evolution Reaction. Nano Lett. 2015,
5, 6015−6021.
39) Zeng, C.; Xie, S.; Yu, M.; Yang, Y.; Lu, X.; Tong, Y. Facile
1
(
Synthesis of Large-Area CeO /ZnO Nanotube Arrays for Enhanced
2
Photocatalytic Hydrogen Evolution. J. Power Sources 2014, 247, 545−
5
(
50.
40) Pu, Z.; Liu, Q.; Tang, C.; Asiri, A. M.; Sun, X. Ni P Nanoparticle
2
Films Supported on a Ti Plate as an Efficient Hydrogen Evolution
Cathode. Nanoscale 2014, 6, 11031−11034.
(
41) Zheng, Y.-R.; Gao, M.-R.; Gao, Q.; Li, H.-H.; Xu, J.; Wu, Z.-Y.;
Yu, S.-H. An Efficient CeO /CoSe2 Nanobelt Composite for
2
Electrochemical Water Oxidation. Small 2015, 11, 182−188.
(
42) Liang, X.; Zheng, B.; Chen, L.; Zhang, J.; Zhuang, Z.; Chen, B.
MOF-Derived Formation of Ni P−CoP Bimetallic Phosphides with
2
Strong Interfacial Effect towards Electrocatalytic Water Splitting. ACS
Appl. Mater. Interfaces 2017, 9, 23222−23229.
(
43) Zhang, L.; Zhang, R.; Ge, R.; Ren, X.; Hao, S.; Xie, F.; Qu, F.; Liu,
Z.; Du, G.; Asiri, A. M.; Zheng, B.; Sun, X. Facilitating Active Species
Generation by Amorphous NiFe-Bi Layer Formation on NiFe-LDH
Nanoarray for Efficient Electrocatalytic Oxygen Evolution at Alkaline
pH. Chem. - Eur. J. 2017, 23, 11499−11503.
(
44) Xie, M.; Yang, L.; Ji, Y.; Wang, Z.; Ren, X.; Liu, Z.; Asiri, A. M.;
Xiong, X.; Sun, X. An Amorphous Co-Carbonate-Hydroxide Nanowire
Array for Efficient and Durable Oxygen Evolution Reaction in
Carbonate Electrolyte. Nanoscale 2017, 9, 16612−16615.
(
45) Xie, F.; Wu, H.; Mou, J.; Lin, D.; Xu, C.; Wu, C.; Sun, X. Ni N@
3
Ni-Ci Nanoarry as a Highly Active and Durable Non-Noble-Metal
Electrocatalyst for Water Oxidation at Near-Neutral pH. J. Catal. 2017,
3
(
56, 165−172.
46) Kibsgaard, J.; Tsai, C.; Chan, K.; Benck, J. D.; Nørskov, J. K.;
Abild-Pedersen, F.; Jaramillo, T. F. New Insights into the Electro-
chemical Hydrogen Oxidation and Evolution Reaction Mechanism.
Energy Environ. Sci. 2015, 8, 3022−3029.
(
47) Nørskov, J. K.; Bligaard, T.; Logadottir, A.; Kitchin, I. R.; Chen, J.
G.; Pandelov, S.; Stimming, U. Trends in the Exchange Current for
Hydrogen Evolution. J. Electrochem. Soc. 2005, 152, J23−J26.
E
DOI: 10.1021/acs.inorgchem.7b02665
����� ����� XXXX, XXX, XXX−XXX
�