Highly efficient hydrogen generation from hydrous hydrazine using a reduced graphene oxide-supported NiPtP nanoparticle catalyst

Article abstract of DOI:10.1016/j.jallcom.2016.08.113

Ultrafine NiPtP nanoparticles (NPs) assembled on reduced graphene oxide (rGO) have been synthesized by a co-reduction route using sodium hypophosphite (NaH₂PO₂) as the source of the nonmetallic P. The well-dispersed ultrafine NiPtP NPs with a diameter about 2?nm can be readily obtained. It is found that these catalysts demonstrate high selectivity and excellent catalytic activity for the decomposition of N₂H₄·H₂O at mild temperature. The enhanced catalytic performance can be attributed to synergistic effect of P-doping and strong high selectivity interaction with graphene support.

Full text of DOI:10.1016/j.jallcom.2016.08.113

Journal of Alloys and Compounds 690 (2017) 783e790
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: http://www.elsevier.com/locate/jalcom
Highly efficient hydrogen generation from hydrous hydrazine using a
reduced graphene oxide-supported NiPtP nanoparticle catalyst
,
,
Tong Liu a **, Jianhua Yu a, Haiyan Bie b *, Zongrui Hao c
a College of Materials Science and Engineering, Qingdao University of Science and Technology, No. 53 Zhengzhou Road, Qingdao, Shandong, 266000, China
b College of Chemistry and Chemical Engineering, Ocean University of China, No. 238 Songling Road, Qingdao, Shandong, 266000, China
c Institute of Oceanographic Instrumentation, Shandong Academy of Sciences, No. 28 Zhengjiang Road, Qingdao, Shandong, 266000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Ultrafine NiPtP nanoparticles (NPs) assembled on reduced graphene oxide (rGO) have been synthesized
by a co-reduction route using sodium hypophosphite (NaH2PO2) as the source of the nonmetallic P. The
well-dispersed ultrafine NiPtP NPs with a diameter about 2 nm can be readily obtained. It is found that
these catalysts demonstrate high selectivity and excellent catalytic activity for the decomposition of
N2H4$H2O at mild temperature. The enhanced catalytic performance can be attributed to synergistic
effect of P-doping and strong high selectivity interaction with graphene support.
Received 4 July 2016
Received in revised form
10 August 2016
Accepted 15 August 2016
Available online 21 August 2016
© 2016 Elsevier B.V. All rights reserved.
Keywords:
NiPtP catalyst
Graphene
Dehydrogenation
Hydrous hydrazine
1. Introduction
Recently, it has been reported that bimetallic NPs based on
nickel and Rh [5,13e15], Pt, Ir [7,16], or Fe [17,18] exhibited fast
Hydrogen with huge applications for the future energy has
drawn considerable attentions because of its clean and environ-
mental nature [1e6]. Recently the developments in chemical
hydrogen storage materials have been paid more attention to, such
as hydrazine monohydrate (N2H4$H2O), which is a liquid over a
wide range of temperatures and has a H2 storage capacity as high as
8.0 wt% [7e9]. Hydrogen stored in hydrazine monohydrate could
be released via complete decomposition method (Eqn (1)) [10e12],
making nitrogen as the only byproduct. However, from the
perspective of hydrogen storage application, the undesired reaction
pathway (eqn (2)) should be avoided.
reaction kinetics and high hydrogen selectivity toward hydrogen
generation from aqueous hydrazine solution. Among them, the
NiPt bimetallic NPs exhibited extremely high catalytic activity
[19e24]. To optimize catalytic property, effectively controlling the
dispersion and size of the NiPt NPs is fundamental. Hence, appli-
cable supports have been designed for controlling the agglomer-
ation and size of metal NPs. Graphene, as a single-layer of sp2
carbon lattices, is an effective support for growing and anchoring
of NPs [25,26]. Although many studies have focused on NiPt NPs
loading on graphene by co-reduction of nickel and platinum salts
solution [19,22,23], doping bimetallic NPs with a non-metal
element, such as B, P, and N, has rarely been reported. Zhang's
group reported that boron-doping RhNiB NPs showed excellent
catalytic activity and high stability towards selective and complete
decomposition of hydrous hydrazine under ambient conditions
[25]. In addition, the influence of phosphorus on the size and
distribution of NPs has been also evaluated [27,28]. Therefore,
developing metalloid-doped NPs might be an effective way toward
rational design cost-effective and high performance catalysts
for decomposition of hydrous hydrazine. Herein, we develop a
one-step co-reduced route to construct NiPtP NPs on reduced
graphene oxide (rGO) using sodium hypophosphite (NaH2PO2) as
the source of the nonmetallic P, which affords high TOF value
H2NNH2 (aq) / N2(g) þ 2H2(g)
3H2NNH2 (aq) / N2(g) þ 4NH3(g)
(1)
(2)
* Corresponding author. College of Chemistry and Chemical Engineering, Ocean
University of China, No. 238 Songling Road, Qingdao, Shandong, 266000, China.
** Corresponding author. College of Materials Science and Engineering, Qingdao
University of Science and Technology, No. 53 Zhengzhou Road, Qingdao, Shandong,
266000, China.
E-mail address: haiyanbie@ouc.edu.cn (H. Bie).
http://dx.doi.org/10.1016/j.jallcom.2016.08.113
0925-8388/© 2016 Elsevier B.V. All rights reserved.

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T. Liu et al. / Journal of Alloys and Compounds 690 (2017) 783e790
(224 hꢀ1 at 298 K and 742 hꢀ1 at 323 K) for hydrous hydrazine
dehydrogenation.
centrifugation, washed with water and dried under vacuum at
room temperature for 12 h.
Additionally, the NiPtP catalyst without GO was also prepared
using the similar synthetic procedure.
2. Experimental
2.2.3. Syntheses of NiPt/rGO catalysts
2.1. Materials
NiPt/rGO catalysts were prepared by in-situ reduction of
NiCl2$6H2O and H2PtCl6$6H2O in water solution by used NaBH4 as
reducing agent. In a typical experiment, 20 mg GO were dissolved
in 25 mL of water. Ultrasonication was required to get a uniform
Hydrazine monohydrate (H2NNH2$H2O, Aladdin reagent Co.,
Ltd, >98%), nickel(II) chloride hexahydrate (NiCl2$6H2O, Sinopharm
Chemical Reagent Co., Ltd, >98%), chloroplatinic acid hexahydrate
(H2PtCl6$6H2O, Sigma-Aldrich Co. LLC, 99%), sodium hypo-
phosphite (NaH2PO2, Aladdin reagent Co., Ltd, 99%), sodium boro-
hydride (NaBH4, Sinopharm Chemical Reagent Co., Ltd, >96%),
isopropanol (C3H8O, Aladdin reagent Co., Ltd, 99%), potassium
permanganate (KMnO4, Sinopharm Chemical Reagent Co., Ltd,
ꢁ99.5%), graphite power (Sinopharm Chemical Reagent Co., Ltd,
ꢁ99.85%), hydrogen peroxide (H2O2, Sinopharm Chemical Reagent
Co., Ltd, ꢁ30%), phosphoric acid (H3PO4, Sinopharm Chemical Re-
agent Co., Ltd, AR), sulfuric acid (H2SO4, Sinopharm Chemical Re-
agent Co., Ltd, 95e98%), sodium carbonate (Na2CO3, Sinopharm
Chemical Reagent Co., Ltd, >96%) were used without further puri-
fication. De-ionized water with the specific resistance of
dispersion. Then, 7 mL nickel chloride solution (0.01 mol Lꢀ1
)
and 3 mL chloroplatinic acid solution (0.01 mol Lꢀ1) was added into
the GO solution. A freshly prepared 10 mL NaBH4 solution (8 wt %)
was added into the above mixture under vigorous stirring at 25 ꢂC.
The resulted mixture was stirred for 20 min. The NiPt/rGO catalysts
were obtained by washing with water and centrifugation.
2.3. Catalyst characterization
Powder X-ray diffraction (XRD) measurements were performed
on D-MAX 2500/PC Powder X-ray diffractometer using Cu K
a
(l
¼ 0.15405 nm) radiation (40 kV, 40 mA). Transmission electron
18.2 MU$cm was obtained by reversed osmosis followed by ion-
exchange and filtration.
microscopy (TEM) images and high-resolution STEM measure-
ments were obtained using Tecnai G2 F30 S-Twin instrument with
a field emission gun operating at 200 kV. X-ray photoelectron
spectroscopy (XPS) measurement was performed with ESCALAB
250Xi spectrophotometer. Mass spectrometry (MS) analysis of the
generated gas was performed using an OmniStar GSD320 mass
spectrometer, wherein Ar was chosen as the carrying gas. The metal
contents of the catalyst were analyzed using inductively coupled
plasma atomic emission spectroscopy (ICPeAES) on Leeman PRO-
FILE SPEC.
2.2. Experimental
2.2.1. Graphene oxide (GO) preparation
GO was synthesized according to the reported procedure
[29,30]. Firstly, a 9:1 mixture of concentrated H2SO4/H3PO4
solution (180:20 mL) was added to the mixture of graphite
power (1.5 g) and KMnO4 (9 g) and then the solution was
kept at 323 K with a water bath for 12 h. The solution was
cooled to room temperature and poured into a flask con-
taining ice (200 g) and H2O2 (30%, 1.5 mL). The resultant so-
lution was centrifuged to obtain the product. The product was
washed by deionized water, 30% diluted hydrochloric acid and
absolute ethyl alcohol for many times and dried under vacuum
at 25 ꢂC.
2.4. Catalytic performance
An aqueous suspension (4 ml) containing the as-prepared
catalysts and NaOH was placed in a two-neck round-bottom
flask (30 mL), which was placed in a water bath under ambient
atmosphere. The reaction started when 0.1 mL of hydrazine
monohydrate was injected into the mixture using a syringe. A
gas burette filled with water was connected to the reaction flask
to measure the volume of released gas. The gas released during
the reaction was passed through a HCl solution (1.0 M) before
it was measured volumetrically. The molar ratios of metal/
N2H4$H2O were theoretically fixed at 0.005 for all the catalytic
reactions.
2.2.2. Syntheses of NiPtP/rGO nanocatalysts
In a typical experiment, 20 mg GO was dissolved in 25 mL
mixture of water and isopropyl alcohol (v:v ¼ 4:1). Ultra-
sonication was required to get a uniform dispersion. Then, 7 mL
nickel chloride solution (0.01 mol Lꢀ1) and 3 mL chloroplatinic
acid solution (0.01 mol Lꢀ1) was added into the GO solution.
The resulted mixture was stirred for 6 h. A 15 mL aqueous so-
lution of sodium hypophosphite (0.02 mol Lꢀ1) was slowly
dripped into the resulted mixture under vigorous stirring.
The pH of the mixture was adjusted to 10 by adding 0.5 M
2.5. Durability testing of the catalysts
For testing the durability of NiPt/rGO catalysts, 0.1 mL of hy-
drazine monohydrate was subsequently added into the reaction
flask after the completion of the first-run decomposition of
Na2CO3, subsequently heated to 80 ꢂC for
cooled in air. The NiPtP/rGO nanocatalysts were collected by
8 h, and then
Fig. 1. Schematic representation of the preparation of the NiPtP/rGO catalyst.

T. Liu et al. / Journal of Alloys and Compounds 690 (2017) 783e790
785
Fig. 2. TEM images of the Ni0.7Pt0.3P/rGO (a) and HRTEM images of the Ni0.7Pt0.3P/rGO (b); high-angle annular dark-field STEM (HAADF-STEM) image of Ni0.7Pt0.3P/rGO (c); HAADF
image (d) and corresponding element mapping of Pt (e), Ni (f) and P (g); TEM images of the Ni0.7Pt0.3/rGO by NaBH4 reduction (h, i).
N2H4$H2O. Such test cycles of the catalyst for the decomposition
of N2H4$H2O were carried out for 5 runs at 323 K by adding
N2H4$H2O.
number of Ni and Pt atoms in catalyst, which is calculated from the
equation as follow:
TOF ¼ 2P0V=ð3RTnNiPttÞ
2.6. Calculation of turnover frequency (TOF)
where P0 is the atmospheric pressure (101325 Pa), V is the final
The TOF reported here is an apparent TOF value based on the
generated volume of H2/N2 gas, R is the universal gas constant

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T. Liu et al. / Journal of Alloys and Compounds 690 (2017) 783e790
(8.3145 m3 Pa molꢀ1 Kꢀ1), T is the room temperature (298 K), nNiPt
is the total mole number of Ni and Pt atoms in catalyst and t is the
completion time of the reaction in hour.
3. Results and discussion
3.1. Physical characteristics of NiPtP/rGO and NiPt/rGO catalysts
The synthesis of NiPtP/rGO catalysts is illustrated in Fig. 1. In
a typical synthesis, the NiPtP NPs supported graphene were
prepared by slowly adding sodium hypophosphite solution into
the precursor solution containing NiCl2, H2PtCl4 and GO at room
temperature. Subsequently, the aqueous solution of sodium
hypophosphite was slowly dripped into the resulted mixture
under vigorous stirring. The pH of the mixture was adjusted to 10
by adding 0.5 M Na2CO3, subsequently heated to 80 ꢂC for 8 h and
then cooled in air. The NiPtP/rGO composites were obtained after
reaction at 90 ꢂC for 8 h under magnetic stirring and centrifugal
separation. The microstructure of NiPtP/rGO was characterized by
transmission electron microscopy (TEM) (Fig. 2a) and high-
resolution TEM (HRTEM) (Fig. 2b). The TEM and high-angle
annular dark-field scanning TEM (HAADF-STEM) (Fig. 2c) im-
ages of NiPtP/rGO show that discrete NiPtP NPs are homoge-
neously dispersed on rGO with an average size of 2 nm (Fig. S1).
The particle size of the NiPtP NPs in this study is much smaller
than that reported by Zhang et al. [31], who prepared dendritic
NiPtP alloy without any supports. In addition, the particle size of
the NiPtP NPs in this study is also much smaller than the NiPt/
rGO NPs synthesized by NaBH4 reduction (Fig. 2h). In Fig. 2b,
the d-spacing with NiPtP NPs is 0.215 nm slightly larger than
0.212 nm of NiPt NPs because of distorting lattice of NiPt alloy
by P-doping [32,33]. The elemental mappings of Ni, Pt and P
(Fig. 1eeg) corresponding to HAADF-STEM images reveal that Ni,
Pt and P atoms were homogeneously dispersed throughout the
NPs. From the results of inductively coupled plasma mass spec-
trometry (ICP-MS) in Table 1, the relative compositions of the
NiPtP NPs yield the following compositions: 0.70 at% Ni, 0.295 at
% Pt, and 0.19 at% P in the NiPtP/rGO. The powder XRD is used for
analyzing the crystalline structures of the prepared NPs (Fig. 3).
All the powder XRD patterns of NiPtP/rGO and NiPt/rGO catalysts
exhibit a broad diffraction peak between 20ꢂ and 30ꢂ, corre-
sponding to the reduced graphene oxide. As for the NiPt/rGO
samples, the diffraction peak at 41ꢂ is attributed to the (111)
plane of crystalline NiPt NPs. Unlike NiPt/rGO catalysts, the
diffraction intensity of NiPtP/rGO catalysts has significantly
reduced. The results indicate that the NiPtP NPs have small size.
Besides, there is no characteristic diffraction peak of metal
phosphides in XRD pattern of NiPtP/rGO catalysts, which dem-
onstrates that the well-dispersed ultrafine NiPtP NPs are sup-
ported on rGO by one-step co-reduced route using NaH2PO2 as a
reductant.
Fig. 3. XRD patterns of Ni0.7Pt0.3P/rGO before (a) and after stability test (b) and
Ni0.7Pt0.3/rGO through the reduction of NaBH4 (c).
doublets with a spinorbit separation. The two peaks located at
74.2 eV and 70.8 eV could be assigned to elemental Pt0 4f5/2 and Pt0
4f7/2, respectively. In addition, compared with NiPt/rGO, a definite
negative shift in the binding energy of Pt 4f is found in NiPtP/rGO.
Ⅴ
The P 2p peaks at 131.5 and 132.3 eV are assigned to Pꢂ and P ,
respectively (Fig. 4b). The peak at 131.5 eV is positively shifted
1.1 eV compared with that of pure phosphorus (130.4 eV). The
positive shift of the P 2p peak of P indicates that there is a strong
interaction between P, Ni, and Pt. These results further demonstrate
the electron interactions occur among P, Ni, and Pt atoms in NiPtP
NPs. Compared with NiPt/rGO, the Ni 2p binding energies of NiPtP/
rGO were negatively shifted (Fig. 4c, d). In Fig. S2, the 2p peaks of
Ni0 appear at 852.3 and 869.6 eV were observed. The formation of
oxidized Ni observed at 857.4 and 874.5 eV most likely occurred
during the sample preparation process for XPS measurements.
Additionally, the peak at 284.5 eV is assigned to the binding energy
of C 1s (Fig. S2).
3.2. Catalytic activities for decomposition of N2H4·H2O by NiPtP/
rGO and NiPt/rGO
The catalytic performances of NixPt1-xP/rGO (0 ꢃ x ꢃ 1) for H2
generation from N2H4$H2O has been investigated at 323 K with a
constant molar ratio of catalyst/N2H4$H2O ¼ 0.05 (Fig. 5a). It can
be seen that the catalytic activity and selectivity for hydrogen
were strongly dependent on the Ni/Pt molar ratio. NixPt1-xP/rGO
catalysts show high catalytic and high H2 selectivity activity at
x ¼ 0.6 to 0.7. Among all the NixPt1-xP/rGO catalysts investigated,
Ni0.7Pt0.3P/rGO exhibits the highest catalytic activity with the TOF
value of 742 hꢀ1, which is higher than most of the reported values
in Table 2. Mass spectrometry (MS) results further confirm the
formation of H2 and N2 and the absence of NH3 in the released gas
(Fig. 6).
Fig. 4 shows XPS spectra of NiPtP/rGO in the P 2p, Pt 4f, Ni 2p,
and C 1s regions. The Pt 4f peak can be fitted to two pairs of
Table 1
ICP-MS results of different catalysts.
Catalyst
Ni Pt P initial ratio
Ni Pt P finial ratio
To study the effects of nonmetallic element P on catalytic
performance, Ni0.7Pt0.3/rGO NPs have been synthesized for com-
parison. As shown in Fig 5b, their catalytic activity and hydrogen
selectivity are both inferior to those of Ni0.7Pt0.3P/rGO NPs. The
catalytic activity enhancement of these NiPtP/rGO NPs is likely
caused by their ultrafine size and the doping of non-metallic
phosphorus element with abundant valence electrons, which
Ni0.8Pt0.2P/rGO
Ni0.7Pt0.3P/rGO
Ni0.6Pt0.4P/rGO
Ni0.5Pt0.5P/rGO
Ni0.4Pt0.5P/rGO
Ni0.7 Pt0.3/rGO
8:2:30
7:3:30
6:4:30
5:5:30
4:6:30
7:3
81:18:34
67:28:19
60:40:20
51:49:12
41:60:13
70:30
Ni0.7Pt0.3
P
7:3:30
74:29:31

T. Liu et al. / Journal of Alloys and Compounds 690 (2017) 783e790
787
Fig. 4. XPS spectra of Pt 4f (a), P 2p (b), Ni 2p (c), and is the magnified spectra of Ni 2p between 850 and 862 eV for the Ni0.7Pt0.3P/rGO and Ni0.7Pt0.3/rGO (d).
has been proved to modulate the electronic structure of metal
elements [33]. It was reported that the third-body effect and
the d-band center shift effect account for improve the bimetallic
adding NaOH has been comparatively tested. As shown in
Fig 5c, the dehydrogenation is incomplete and slow without
NaOH, which is consistent with the previous results. It has
been found that the catalytic activity increases with the
amount of NaOH until the value reaches 4 mmol, and a further
increase in the amount of NaOH shows little effect on the
catalytic performance. The possible reason for the effects of the
NaOH additive may be explained as below: the existence of
OHꢀ ions can decrease the concentration of undesirable N2H5þ
(N2Hþ5 þ OHꢀ ! N2H4 þ H2O) in aqueous solution and assist
the rate-determining deprotonation step (N2H4 / N2H3* þ H*)
in the decomposition process of N2H4 to N2 and H2. Addition-
ally, in view of the chemical equilibrium, a strong alkaline
environment will inhibit the generation of the basic byproduct
NH3, which raises the H2 selectivity.
catalysts' activity [45e48]. The doping of
P can effectively
modify the d-band electron density of Pt [49,50]. It is reasonable
to understand that the doping of P leads to increase of the
catalytic active surface areas of NiPtP by changing interme-
tallic electronic interaction. On the other hand, The Ni0.7Pt0.3
particles on rGO have a poor size distribution with average from
3 to 4 nm (Fig. S1). The addition of P could reduce the aggre-
gation of NiPt NPs, resulting in an ultrafine size and narrow size
distribution.
For comparison, the catalytic activity of Ni0.7Pt0.3P catalysts
without support is also tested (Fig. 5b and S3). The NiPtP
aggregate to form large particles without graphene support in the
TEM image. The catalytic activity and hydrogen selectivity are
lower than those of NiPtP and NiPt NPs supported on graphene,
highlighting the positive effect of utilization graphene as a two-
dimensional support in facilitating the electron transfer and
mass transport.
In addition, the recycling stability of Ni0.7Pt0.3P/rGO NPs was
tested at 323
K by adding aqueous hydrous hydrazine
(1.96 mmol) to the catalyst after the reaction completion for the
last run. It is evident from Fig. 5d, the H2 selectivity and activity
have almost no any decline after five runs. TEM measurements of
the recovered catalysts show no obvious change in the particle
size (Fig. S4.), indicating that the Ni0.7Pt0.3P/rGO catalyst has high
stability and durability under the current dehydrogenation of
N2H4$H2O.
Besides the good dispersion of the ultrafine NPs and NiPt
synergistic coupling with nonmetallic phosphorus, the presence
of NaOH has a great effect on the catalytic activity of catalysts.
The hydrogen generation from hydrazine solution with/without

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T. Liu et al. / Journal of Alloys and Compounds 690 (2017) 783e790
Fig. 5. Volume of the generated gas (H2 þ N2) versus time for the dehydrogenation of hydrous hydrazine with different Pt/Ni molar ratios (a) and time-course plots for the
decomposition of hydrous hydrazine catalyzed by Ni0.7Pt0.3P/rGO, Ni0.7Pt0.3/rGO and Ni0.7Pt0.3 respectively (b); Ni0.7Pt0.3P/rGO in different amounts of NaOH solution (c); durability
test of Ni0.7Pt0.3P/rGO for dehydrogenation of hydrazine hydrate in aqueous 0.5 M NaOH solution (d) (nmetal/nN2H4$H2O ¼ 0.05, 323 K).
In order to obtain the activation energy (Ea) of the N2H4$H2O
decomposition catalyzed by the Ni0.7Pt0.3P/rGO NPs, the reactions
at different temperatures (298e333 K) were carried out and the
results are shown in Fig. 7a. As expected, the gas generation rate
over the Ni0.7Pt0.3P/rGO NPs catalyst greatly depends on the
reaction temperatures. The catalytic reactions are completed in
10.5, 5.5, 3.2, and 2.2 min at 298, 313, 323, and 333 K, respectively,
which correspond to TOF values of 224, 427, 742, and 1050 hꢀ1. The
Arrhenius plot of ln TOF vs. 1/T for this catalyst is plotted in Fig. 7b,
from which Ea was calculated as 50.7 kJ molꢀ1
.
Table 2
Catalytic activities of different catalysts for the dehydrogenation of hydrous hydrazine.
Catalyst
Solvent/medium
Temp. (K)
Selectivity H2 for (100%)
TOF (hꢀ1
)
Ea (kJ molꢀ1
)
Ref.
Ni0.7Pt0.3P/rGO
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Without additive
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Aqueous NaOH
Without additive
Without additive
Without additive
Without additive
Without additive
323
298
323
293
323
323
323
323
293
298
298
323
323
323
298
298
303
303
299
298
298
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
99
742
224
2056
528
350
395
570
706
942
150
68
170
28.8
140
28
28.1
12.4
16.5
11
50.7
50.7
33.39
48.1
55.5
38.8
36.6
50.15
41.6
This work
This work
[23]
[19]
[10]
[15]
[34]
[35]
[36]
[37]
[25]
[38]
[39]
[14]
[40]
[23]
[41]
Pt0.6Ni0.4/PDA-rGO
Ni3Fe/C
Ni88Pt12/MIL-101
Rh55Ni45/Ce(OH)
Ni37Pt63/g-C3N4
(Ni3Pt7)0.5-(MnOx)0.5/NPC-900
cubic Rh2Ni
Ni6Pt4-SF
Ni3Pt7/graphene
Pt60Ni40-CNDs
Ni0.6Fe0.4Mo
Ni66Rh34@ZIF-8
Rh4.4Ni/graphene
Ni0.9Pt0.1/Ce2O3
NiIr0.059/Al2O3-HT
NiPt0.057/Al2O3-HT
Ni1.5Fe1.0/(MgO)3.5
Rh4Ni
49.4
43.9
50.7
58.1
42.3
49.3
34
97
99
100
100
[42]
[43]
[44]
[7]
4.8
2.2
Ni0.95Ir0.05

T. Liu et al. / Journal of Alloys and Compounds 690 (2017) 783e790
789
4. Conclusions
In summary, we have developed a co-reduction method to
prepare P-doping NiPtP NPs on graphene by using NaH2PO2 as a
reducing agent. The well-dispersed ultrafine NiPtP NPs with a
diameter about 2 nm can be readily obtained. It is found that these
catalysts show high selectivity and excellent catalytic activity for
the decomposition of N2H4$H2O at mild temperature. Such excel-
lent catalytic performance can be attributed to synergistic effect of
P-doping and strong interaction with graphene support. The pre-
sent work provides an effective strategy to immobilize ultrafine P-
doping NPs on graphene as the catalysts of N2H4$H2O decomposi-
tion, which may be beneficial for the application of N2H4$H2O as a
hopeful chemical hydrogen storage material.
Acknowledgments
This work was financially supported by the National Natural
Science Foundation of China (Grant No. 51306166 and No.
51206101).
Fig. 6. MS profile for the gases released from the decomposition reaction of hydrous
hydrazine in aqueous NaOH solution (0.5 M) by Ni0.7Pt0.3P/rGO at 50 ꢂC.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.jallcom.2016.08.113.
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