Immobilization of Ni–Pt nanoparticles on MIL-101/rGO composite for hydrogen evolution from hydrous hydrazine and hydrazine borane

Article abstract of DOI:10.1016/j.jallcom.2020.155426

As an ideal hydrogen supplier in liquid phase, hydrous hydrazine has gained a lot of attention for safe and efficient storage as well as transportation of hydrogen. Herein, a low Pt-containing Ni–Pt bimetallic catalyst immobilized on novel MIL-101/rGO composite has been prepared by a facile impregnation-reduction approach. Unexpectedly, the resultant Ni_0.9Pt_0.1/MIL-101/rGO catalyst exhibits optimal catalytic performance and 100% H₂ selectivity for hydrogen evolution from hydrous hydrazine under alkaline conditions at 323 K, giving a turnover frequency (TOF) value of 960.0 h^?1, which is a relatively higher value ever reported heterogeneous catalysts. Even at room temperature, Ni_0.9Pt_0.1/MIL-101/rGO catalyst shows excellent catalytic activity for dehydrogenation of hydrazine as well as hydrazine borane. In addition, the Ni_0.9Pt_0.1/MIL-101/rGO catalyst also exhibits excellent durability. Even after eight recycles, the catalytic activity is no significant decrease, and the H₂ selectivity still remains 100%.

Full text of DOI:10.1016/j.jallcom.2020.155426

Journal Pre-proof
Immobilization of Ni–Pt nanoparticles on MIL-101/rGO composite for hydrogen
evolution from hydrous hydrazine and hydrazine borane
Hongtao Zou, Shiliang Zhang, Xiaoling Hong, Qilu Yao, Yan Luo, Zhang-Hui Lu
PII:
S0925-8388(20)31789-8
DOI:
https://doi.org/10.1016/j.jallcom.2020.155426
JALCOM 155426
Reference:
To appear in: Journal of Alloys and Compounds
Received Date: 15 January 2020
Revised Date: 23 April 2020
Accepted Date: 28 April 2020
Please cite this article as: H. Zou, S. Zhang, X. Hong, Q. Yao, Y. Luo, Z.-H. Lu, Immobilization of Ni–Pt
nanoparticles on MIL-101/rGO composite for hydrogen evolution from hydrous hydrazine and hydrazine
borane, Journal of Alloys and Compounds (2020), doi: https://doi.org/10.1016/j.jallcom.2020.155426.
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Author contributions
Hongtao Zou: Methodology, Validation, Formal analysis, Investigation, Data
curation, Writing-Review and Editing. Shiliang Zhang: Methodology, Investigation,
Formal analysis, Writing-Original draft. Xiaoling Hong: Methodology, Validation,
Formal analysis. Qilu Yao: Resources, Formal analysis, Review and Editing. Yan Luo:
Formal analysis, Review and Editing. Zhang-Hui Lu: Conceptualization, Formal
analysis, Resources, Supervision, Writing-Review and Editing, Project administration,
Funding acquisition.

Graphical Abstract
A low Pt-containing Ni-Pt nanocatalyst immobilized on MOF/rGO composite has been
synthesized for hydrogen production from hydrous hydrazine and hydrazine borane.

Immobilization of Ni-Pt nanoparticles on MIL-101/rGO composite for
hydrogen evolution from hydrous hydrazine and hydrazine borane
Hongtao Zoua, Shiliang Zhanga, Xiaoling Honga, Qilu Yaoa, Yan Luob, Zhang-Hui Lua,*
aInstitute of Advanced Materials (IAM), College of Chemistry and Chemical Engineering,
Jiangxi Normal University, Nanchang 330022, P.R. China
bCollege of Civil Aviation Safety Engineering, Civil Aviation Flight University of China,
Guanghan 618307, P.R. China
*Corresponding authors.
E-mail: luzh@jxnu.edu.cn (Z.-H. Lu)
Abstract
As an ideal hydrogen supplier in liquid phase, hydrous hydrazine has gained a lot of
attention for safe and efficient storage as well as transportation of hydrogen. Herein, a
low Pt-containing Ni-Pt bimetallic catalyst immobilized on novel MIL-101/rGO
composite has been prepared by a facile impregnation-reduction approach.
Unexpectedly, the resultant Ni0.9Pt0.1/MIL-101/rGO catalyst exhibits optimal catalytic
performance and 100% H2 selectivity for hydrogen evolution from hydrous hydrazine
under alkaline conditions at 323 K with, giving a turnover frequency (TOF) value of
960.0 h-1, which is a relatively higher value ever reported heterogeneous catalysts. Even
at room temperature, Ni0.9Pt0.1/MIL-101/rGO catalyst shows excellent catalytic activity
for dehydrogenation of hydrazine as well as hydrazine borane. In addition, the
Ni0.9Pt0.1/MIL-101/rGO catalyst also exhibits excellent durability. Even after eight
recycles, the catalytic activity is no significant decrease, and the H2 selectivity still
remains 100%.
1

Keywords: Hydrazine; Nanoparticle; Metal-organic framework; Graphene; Hydrogen
evolution
1. Introduction
Hydrogen energy, as a highly-efficient, sustainable, pollution-free, and abundant
source of secondary energy, has attracted increasing interest [1-3]. However, safely
storing and transporting hydrogen remains a grand challenge for the achievement of
hydrogen economy society [4-6]. Recently, more and more efforts have been made to
study chemical hydrides as efficient carriers for chemical hydrogen storage [7-9].
Hydrous hydrazine (N2H4∙H2O) has great potential as a promising liquid chemical
hydrogen storage material for storage and transportation of hydrogen, because of its
high hydrogen content (8.0 wt%), stable liquid state, nontoxicity, and clean emissions
(only nitrogen as byproduct via equation (1)) [10-12]. To this end, the incomplete
decomposition of hydrazine to ammonia (NH3) via equation (2) should be avoided
[13-15]. Consequently, the key is to develop simple and effective strategies to
synthesize a high-efficient and low-cost heterogeneous catalyst for complete
dehydrogenation of hydrazine.
N2H4(l) → N2(g) + 2H2(g)
(1)
(2)
3N2H4(l) → N2(g) + 4NH3(g)
In recent years, noble-metal-containing nickel-based bimetallic heterogeneous
nanocatalysts, such as Ni-Rh [16-18], Ni-Pt [19-21], Ni-Ir [22, 23], and Ni-Pd [24-26],
have been synthesized and explored for dehydrogenation of hydrazine. Numerous
studies have demonstrated that Ni-Pt catalysts possess excellent catalytic properties for
2

hydrazine decomposition [27-29]. Generally, organic surfactants could help to control
and stabilize the metal nanoparticles (NPs), but the metal active sites may be blocked
after involved organic stabilizers, leading to a deterioration of catalytic performance [30,
31]. Loading the metal NPs onto the inorganic support with large specific surface area
could stabilize the metal NPs without aggregation [29, 32]. Recently, metal-organic
frameworks (MOFs) and graphene oxide (GO) have been considered as promising
carriers due to their unique structure and properties [33-39]. To be noted, lots of studies
find that the catalytic performance and stability of MOFs/GO composites, to some
extent, have been enhanced in comparison with pure MOFs and GO [40-43].
Herein, low noble-metal-containing Ni-Pt NPs have been immobilized on
MIL-101/rGO composite using the facile impregnation-reduction method without the
help of surfactant. Interestingly, the resultant Ni0.9Pt0.1/MIL-101/rGO shows excellent
catalytic performances and 100% H2 selectivity for decomposition of hydrazine and
hydrazine borane at 323 K, affording turnover frequency (TOF) values of 960.0 and
1579.9 h-1, respectively.
2. Materials and methods
2.1. Materials
Graphite powder (J&K Chemical, 99%), sulfuric acid (H2SO4, Nanchang Xinguang
Fine Chemical Works, 98%), phosphorus pentoxide (P2O5, Tianjin Fuchen Chemical
Reagent, 98%), potassium permanganate (KMnO4, Nanchang Xinguang Fine Chemical
Works, >99.5%), potassium persulfate (K2S2O8, Tianjin Fuchen Chemical Reagent,
3

99.5%), n-pentane (C5H12, Sigma-Aldrich, 99.5%), hydrogen peroxide (H2O2, Tianjin
Fuchen Chemical Reagent, 30%), chromium nitrate nonahydrate (Cr(NO3)3∙9H2O,
Aladdin, 99%), aqueous hydrofluoric acid (HF, Aladdin, 40 wt%), terephthalic acid
(H2BDC, Aladdin, 99%), nickel (II) chloride hexahydrate (NiCl2∙6H2O, Aladdin, 98%),
potassium (II) tetrachloroplatinate (K2PtCl4, J&K Chemical, 99.95%), hydrous
hydrazine (N2H4∙H2O, Sigma-Aldrich, 98%), 1,4-dioxane (C4H8O2, J&K Chemical,
99.8%), sodium borohydride (NaBH4, Acros, 98%), sodium hydroxide (NaOH, Tianjin
Fuchen Chemical Reagent, 96%), and hydrazine hemisulfate salt (N2H4∙1/2H2SO4,
Sigma-Aldrich, 99.5%) were from commercial sources and used as received. Hydrazine
borane (N2H4BH3) was prepared according to the procedure reported in literature [25,
44].
2.2. Synthesis of MIL-101/GO composite
MIL-101/GO composite was synthesized using a similar method according to the
procedure for synthesis of MIL-101 [27, 45]. 4.0 g of Cr(NO3)3∙9H2O, 400 mg of
as-prepared GO, 0.5 mL of HF, and 1.6 g of H2BDC were dispersed in 70 mL water. Then,
the above suspension was heated to 493 K and maintained for 8 h. After the resultant
suspension was cooled to room temperature, the product was washed with water and
ethanol. To further remove the un-reacted H2BDC, the as-synthesized sample was soaked
in ethanol solution at 353 K for 24 h, then in NH4F (1.0 M) solution at 343 K for another
24 h. Finally, the resulting sample was washed with ethanol three times and followed by
drying under vacuum at 323 K overnight.
2.3. Synthesis of NiPt/MIL-101/rGO
4

NiPt/MIL-101/rGO catalyst was synthesized by a facile impregnation-reduction
approach. Typically, 65 mg of as-synthesized MIL-101/GO composite, 0.09 mmol of
NiCl2∙6H2O, and 0.01 mmol of K2PtCl4 were ultrasonically dispersed in 5 mL water. The
resultant suspension was keep stirring for 6 h to impregnate the metal salts. Subsequently,
30 mg of NaBH4 was added into the above mixture to obtain Ni0.9Pt0.1/MIL-101/rGO
nanocatalyst. NixPt1-x/MIL-101/rGO nanocatalysts with other different molar ratios of
Ni/Pt (0:1, 0.3:0.7, 0.5:0.5, 0.7:0.3, and 1:0) were prepared following the same procedure
except that NiCl2∙6H2O and K2PtCl4 with different molar ratios were added.
Ni0.9Pt0.1/MIL-101/rGO nanocatalysts with different metal loadings were also prepared
by changing the addition contents of MIL-101/GO supports. Additionally, the
Ni0.9Pt0.1/rGO and Ni0.9Pt0.1/MIL-101 nanocatalysts were prepared using the similar
method above, by replaced the support material to GO and MIL-101, respectively.
2.4. Catalytic activities
The catalytic reaction equipment used to measure the H2/N2 evolution from hydrous
hydrazine or hydrazine borane is similar to that previously reported [46]. Typically, 5 mL
aqueous suspension containing the obtained catalyst and 5.0 mmol NaOH was added into
the reactor. One port of the reactor was used for measure the volume of the produced gas,
while the other port was directly used to introduce hydrous hydrazine (2.0 mmol) or
hydrazine borane (1.0 mmol). A trap filled with hydrochloric acid (1.0 M) was placed
between the reactor and gas buret to absorb any released NH3. The H2 selectivity (α)
toward hydrogen production from hydrous hydrazine could be calculated on the basis of
equation (3), which can be deduced from equations (1) and (2). The H2 selectivity (β)
5

toward hydrogen generation from hydrazine borane could be evaluated according to
equation (4), which can be deduced from equations (1), (2), and equation (5).
N2H4 → 2αH2 + (2α+1)/3N2 + 4(1-α)/3NH3
N2H4BH3 + 3H2O → B(OH)3 + (3+2β)H2 + (2β+1)/3N2 + 4(1-β)/3NH3 (4)
N2H4BH3(s) + 3H2O(l) → N2H4(l) + B(OH)3(l) + 3H2(g) (5)
(3)
As NH3 is highly solution in hydrochloric acid and water, the gas volume measured by the
gas buret contains only hydrogen and nitrogen, from which the molar ratio λ =
n(H2+N2)/n(N2H4) and γ = n(H2+N2)/n(N2H4BH3) could be calculated [17-20]. Therefore,
the H2 selectivity α and β could be calculated through equations (6) and (7), respectively.
ꢄ
ꢆ
3ꢁ − 1
8
ꢃ Hꢅ + Nꢅ
1
ꢄ ꢆ
ꢀ =
ꢋ =
ꢂꢁ =
ꢈ ≤ ꢁ ≤ 3ꢉꢊ
3
6
ꢄ
ꢆ
ꢃ NꢅHꢇ
ꢄ ꢆ
ꢃ Hꢅ + Nꢅ 10
3ꢌ − 10
8
ꢄ ꢆ
7
ꢂꢌ =
ꢈ
≤ ꢌ ≤ 6ꢉꢊ
ꢄ
ꢆ
3
ꢃ NꢅHꢇBHꢍ
3. Results and discussion
3.1. Synthesis and characterization of catalysts
The procedure of immobilized Ni-Pt NPs on MIL-101/rGO composite is illustrated in
Scheme 1. Briefly, the as-prepared GO was hydrothermally treated together with H2BDC
and Cr(NO3)3∙9H2O to get MIL-101/GO composite material. The resultant MIL-101/GO
composite was dispersed in water through ultrasound, followed by addition of NiCl2 and
K2PtCl4. Finally, NaBH4 as the reducing agent was added to obtain the
NiPt/MIL-101/rGO nanocatalysts. Among all the as-prepared catalysts,
Ni0.9Pt0.1/MIL-101/rGO with 10.0 wt% Ni-Pt loading was selected as a model catalyst for
6

full characterization, because of its excellent dehydrogenation catalytic performance.
The crystal structures of GO, MIL-101, MIL-101/GO, Ni/MIL-101/rGO,
NiPt/MIL-101/rGO, and Pt/MIL-101/rGO samples were characterized by power XRD
(Fig. 1 and Fig. S1). As shown in Fig. 1a and Fig. S1, the characteristic diffraction peaks
of MIL-101 can be apparently observed in MIL-101/GO composite, indicating the
successful formation of MIL-101 crystals on GO [29, 47]. This observation has been
further confirmed by FTIR and Raman spectra (Fig. S2). The characteristic diffraction
peaks of MIL-101 crystal are still retained after loading of metal NPs (Fig. 1a),
suggesting the crystalline structure of MIL-101 is stable during catalyst preparation.
Additionally, the wide-angle XRD pattern of NiPt/MIL-101/rGO shows a broad and
weak diffraction peaks at 2θ = 42.7° (Fig. 1b), which is located between the Ni (111)
(JCPDS no. 04-0850) and Pt (111) (JCPDS no. 04-0802), clearly demonstrating the
formation of the Ni-Pt alloy [21]. Furthermore, XPS measurements were performed to
reveal the elemental compositions and electronic structure of Ni0.9Pt0.1/MIL-101/rGO
nanocatalyst. The survey XPS full spectrum for Ni0.9Pt0.1/MIL-101/rGO shows the
co-existence of Ni, Pt, Cr, C, and O (Fig. S3). As shown in Fig. 2a, the binding energies
for Ni 2p3/2 and Ni 2p1/2 at 852.9 and 870.1 eV are clearly observed in Ni 2p XPS
spectrum, which could be assigned to states of Ni0 [48]. For Pt 4f XPS spectrum, the
binding energies for Pt 4f7/2 and Pt 4f5/2 at 71.6 and 74.9 eV are attributed to states of Pt0
(Fig. 2b) [32]. In addition, the binding energies for Ni 2p3/2 and Ni 2p1/2 at 853.5 and
873.5 eV are corresponded to Ni2+, which could be explained by the surface oxidation of
Ni during the sample preparation process for XPS test [49]. Besides, the Ni 2p3/2 peaks at
7

about 858.2 eV and Ni 2p1/2 peak at about 877.0 eV are assigned to the satellite peaks of
Ni [15]. These results suggest that Ni-Pt NPs composed of metallic Ni, metallic Pt and a
little amount of oxidized Ni have been successfully formed on MIL-101/rGO composite.
The SEM images present that original GO is a thin and wrinkled lamellar structure
(Fig. 3a), while MIL-101 material appears a regular octahedral morphology (Fig. 3b).
The detail morphology of Ni0.9Pt0.1/MIL-101/rGO nanocatalyst was investigated via
TEM. As shown in Fig. 3c,d, and Fig. S4, the Ni-Pt NPs (~9.2 nm, Fig. S5) are well
dispersed on MIL-101/rGO composite surface. The high resolution TEM image shows
the lattice fringes of Ni0.9Pt0.1/MIL-101/rGO nanocatalyst with d-spacing of 0.218 nm
(Fig. 3e), confirming the formation of Ni-Pt (111) planes [27, 50]. Moreover, the SAED
pattern displays a diffraction ring radius with 4.58 1/nm (Fig. 3f), further implying that
the successful formation the structure of Ni-Pt alloy [13]. The corresponding EDX
analysis of Ni0.9Pt0.1/MIL-101/rGO further indicates the existence of Ni, Pt, Cr, C, and O
elements (Fig. S6).
The Brunauer-Emmett-Teller (BET) specific surface areas of as-prepared samples
were determined via nitrogen adsorption-desorption isotherms measurements after
dehydration under vacuum at 373 K for 8 h. As shown in Fig. 4, the BET specific surface
area for MIL-101/GO composite is measured to be 3200 m2·g-1, which is larger than that
of pure MIL-101 (2891 m2·g-1). The pure GO sample prepared in the present work
shows a very low specific surface area of only 18 m2·g-1 (Fig. S7), which is much lower
than that of the real specific surface area of GO dispersed in the solution, probably due to
the overlapping of graphene sheets within the self-aggregation during the drying process
8

[17]. To be noted, there is a distinctly adsorption hysteresis loop in MIL-101/GO
composite, revealing that a new pore space is formed between MIL-101 crystal and GO in
the composite [45]. In addition, the specific surface area of the as-prepared
Ni0.9Pt0.1/MIL-101/rGO nanocatalyst (1371 m2·g-1) is lower than that of MIL-101/GO,
revealing that a part of the pores and/or defects were occupied by Ni-Pt NPs [51]. This
MIL-101/GO composite with high specific surface area is typically beneficial for mass
transfer processes, which can largely increase the catalytic dehydrogenation reaction
dynamics. On the other hand, the porous surface structure could offer steric restriction to
confine and prevent the growth of the metal NPs [29, 33-35].
3.2. Catalytic performances
The catalytic performances for hydrazine decomposition were investigated under
alkaline conditions. As presented in Fig. 5, the Ni0.9Pt0.1/MIL-101/rGO nanocatalyst
performs the best dehydrogenation activity of hydrazine, releasing 3.0 equivalents of
(N2+H2) in only 3.0 min with a TOF value of 960.0 h-1, which is a relatively higher value
over heterogeneous catalysts reported previously for this reaction (Table S1) [8, 11, 14,
17, 22, 23, 29, 52-55]. For comparison, the activities of Ni0.9Pt0.1/MIL-101, Ni0.9Pt0.1/rGO,
pure Ni0.9Pt0.1 NPs, and MIL-101/GO were also measured. Clearly, all these reference
catalysts exhibit much lower catalytic activities than that of Ni0.9Pt0.1/MIL-101/rGO,
giving the corresponding TOF values of 452.8, 158.5, 97.3, and 0 h-1, respectively. This
remarkable catalytic activity could be directly attributed to its unique structure and high
specific surface area.
Then, the effect of Ni/Pt molar ratios in NiPt/MIL-101/rGO nanocatalysts on the
9

catalytic performances for hydrazine decomposition was carefully investigated. As
shown in Fig. 6, the activities and selectivity versus Ni/Pt molar ratios show typical
volcano-shaped profile. The monometallic Ni/MIL-101/rGO exhibits a poor catalytic
performance and H2 selectivity, while the monometallic Pt/MIL-101/rGO is almost
inactive. Interestingly, after addition of Ni to form Ni-Pt alloy, the bimetallic catalysts
exhibit a much higher activity and selectivity compared with their monometallic
counterparts. With the increasing of Ni/Pt molar ratios, the activities of hydrazine
dehydrogenation are increased at first and the optimum catalysis can be obtained by using
a Ni/Pt ratio of 0.9:0.1. A further increase of Ni/Pt molar ratios leads to the loss of
catalytic activities. Meanwhile, ICP-AES analysis confirmed that the Ni/Pt ratios of
as-prepared catalysts match the predesigned trend and the actual contents of Ni and Pt are
close to the nominal values (Table S2). To reveal the optimal metal loadings, the catalytic
activities Ni0.9Pt0.1/MIL-101/rGO nanocatalysts with the different loadings of Ni-Pt NPs
(5.0, 7.5, 10.0, and 12.5 wt%) have been also investigated (Fig. S8). Results show that
Ni0.9Pt0.1/MIL-101/rGO nanocatalyst with 10.0 wt% total Ni-Pt loading exhibits the
highest catalytic activity for hydrazine decomposition. These enhanced catalytic
performances might be not only attributed to the intermetallic synergic effects, but also
the metal-support interaction [51, 56].
To investigate the effect of NaOH, the catalytic performances have been tested with
different NaOH concentrations (Fig. S9). Ni0.9Pt0.1/MIL-101/rGO shows poor activity in
the absence of NaOH with only 2.3 equivalents of (H2 + N2) generated in 29.2 min. As the
NaOH concentration increased to 1.0 M, the catalytic activity is significantly improved.
10

When the NaOH concentration is further increased, it has a negative effect, revealing that
the optimal NaOH concentration was 1.0 M. As demonstrated in Fig. S10, pure NaOH
has no catalytic activity, indicating that NaOH is acted as a promoter, not a catalyst. The
alkaline environment not only promote the rate-determining step of hydrazine
*
decomposition into N2 and H2 (N2H4 → N2H3 + H*), but also inhibit the generation of
byproduct NH3, which raises the H2 selectivity [28, 51, 57].
Furthermore, the effect of reaction temperature on hydrazine dehydrogenation over
optimized Ni0.9Pt0.1/MIL-101/rGO nanocatalyst was investigated. As shown in Fig. 7a,
the catalytic activities are rapidly enhanced with increasing the reaction temperature. The
corresponding TOF values are calculated to be 180.5, 274.6, 638.3, 960.0, and 1363.6 h-1
at 298, 308, 313, 323, and 333 K, respectively (Fig. 7b). According to the rate constant k
of the hydrazine decomposition reaction at different temperatures, the Arrhenius plot of
ln k versus 1/T was plotted in the inset of Fig. 7a, the activation energy (Ea) of
Ni0.9Pt0.1/MIL-101/rGO nanocatalyst for hydrazine decomposition is 50.6 kJ·mol-1. This
value is much lower than most of the heterogeneous catalysts reported previously for this
reaction (Table S2) [8, 11, 14, 17, 22, 23, 29, 52-55].
Recently, hydrazine borane (N2H4BH3), as an emerging chemical hydrogen storage
material, has triggered tremendous attention because of its very high hydrogen density
(15.4 wt%) and satisfactory stability under ambient conditions. The complete hydrogen
release from hydrazine borane can produce 5.0 equivalents of H2 (N2H4BH3 (s) + 3H2O
→ B(OH)3 (l) + N2 (g) + 5H2 (g)) [58-61]. Considering its superior catalytic properties for
hydrazine decomposition, this optimized Ni0.9Pt0.1/MIL-101/rGO nanocatalyst was also
11

used to hydrogen evolution from hydrazine borane at the same condition. As presented in
Fig. 7c, the influence of reaction temperature on dehydrogenation reaction rate of
hydrazine borane was also evaluated. Hydrogen generation from hydrazine borane
decomposition can be finished within 14.7, 4.9, 4.1, 1.9, and 1.1 min at 298, 308, 313, 323,
and 333 K, respectively, corresponding to TOF values of 203.0, 606.1, 717.7, 1578.9, and
2654 h-1 (Fig. 7d). These values are relatively high values among the reported
heterogeneous catalysts [13, 17, 23, 25, 27, 44, 48, 58-60]. The activation energies for
BH3 group hydrolysis (Ea1, Part 1) and N2H4 moiety decomposition (Ea2, Part 2) of
hydrazine borane are determined to be 17.6 and 56.4 kJ·mol-1 (Fig. 7c, inset),
respectively. We further examine briefly the durability of Ni0.9Pt0.1/MIL-101/rGO
nanocatalyst to the decomposition reaction of hydrazine and hydrazine borane. As
presented in Fig. 8, the Ni0.9Pt0.1/MIL-101/rGO nanocatalyst shows excellent durability.
Even after eight recycles, the catalytic activity is no significant decreased, and the H2
selectivity still remains 100%.
4. Conclusions
In summary, we have reported a simple impregnation-reduction strategy for
immobilization of low noble-metal-containing bimetallic Ni-Pt NPs on novel
MIL-101/rGO composite. Unexpectedly, the resultant Ni0.9Pt0.1/MIL-101/rGO
nanocatalyst exhibits excellent catalytic activity and 100% H2 selectivity for hydrogen
evolution from hydrous hydrazine at 323 K under alkaline conditions. The
corresponding TOF reaches 960.0 h-1, which is much higher than most of the
12

heterogeneous catalysts reported to date. The characterization results revealed that the
Ni-Pt NPs were successfully immobilized on MIL-101/rGO composite with unique
structure and high specific surface area. In addition, Ni0.9Pt0.1/MIL-101/rGO
nanocatalyst is also beneficial to high-extent dehydrogenation of hydrazine borane
under the same condition, achieving the 5.0 equivalents of H2 within 1.9 min. What’s
more, even after eight recycles of the catalytic process, the H2 selectivity is maintained
and their initial catalytic activity shows no significant decrease. Such unique strategy
via synthesizing some unique structure and high specific surface area composite to
support metal NPs might benefit to design a series of novel nanocatalysts for the wide
practical application prospect in various catalytic fields.
Acknowledgments
This work was financially supported by the National Natural Science Foundation of
China (Nos. 21763012 and 21802056) and the Natural Science Foundation of Jiangxi
Province of China (No. 20192BAB203009).
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23

List of figure captions
Scheme 1 Schematic illustration for the preparation of NiPt/MIL-101/rGO catalyst.
Fig. 1 (a) Low-angle and (b) wide-angle XRD patterns of MIL-101/GO,
Ni/MIL-101/rGO, NiPt/MIL-101/rGO, and Pt/MIL-101/rGO.
Fig. 2 XPS spectra of (a) Ni 2p and (b) Pt 4f for Ni0.9Pt0.1/MIL-101/rGO catalyst after
argon sputtering for 5 min.
Fig. 3 (a,b) SEM images of the as-prepared GO and MIL-101 samples. (c,d) Low
resolution TEM images, (e) high resolution TEM image, and (f) SAED pattern of the
Ni0.9Pt0.1/MIL-101/rGO catalyst.
Fig. 4 Nitrogen adsorption-desorption isotherms of the as-prepared MIL-101,
MIL-101/GO, and Ni0.9Pt0.1/MIL-101/rGO samples after dehydration under vacuum at
373 K for 8 h.
Fig. 5 (a) Time-course plots and (b) the corresponding TOF values for hydrogen
evolution from N2H4·H2O catalyzed by MIL-101/GO, Ni0.9Pt0.1, Ni0.9Pt0.1/rGO,
Ni0.9Pt0.1/MIL-101, and Ni0.9Pt0.1/MIL-101/rGO in the presence of NaOH (1.0 M) at 323
K (nNi+Pt/nN2H ·H O = 0.05).
4
2
24

Fig. 6 (a) Time-course plots and (b) the corresponding TOF values and H2 selectivity for
hydrogen evolution from N2H4·H2O catalyzed by NixPt1-x/MIL-101/rGO (0 ≤ x ≤ 1.0) in
the presence of NaOH (1.0 M) at 323 K (nNi+Pt/nN2H ·H O = 0.05).
4
2
Fig. 7 Time-course plots and its related Arrhenius plots for hydrogen evolution from
(a,b) N2H4·H2O and (c,d) N2H4BH3 catalyzed by Ni0.9Pt0.1/MIL-101/rGO at different
temperatures.
Fig. 8 Durability tests of Ni0.9Pt0.1/MIL-101/rGO catalyst for hydrogen evolution from
(a) N2H4·H2O and (b) N2H4BH3 at 343 K.
25

Scheme 1 Schematic illustration for the preparation of NiPt/MIL-101/rGO catalyst.

Fig. 1 (a) Low-angle and (b) wide-angle XRD patterns of MIL-101/GO,
Ni/MIL-101/rGO, NiPt/MIL-101/rGO, and Pt/MIL-101/rGO.