H2 Evolution Upon Hydrolysis of Ammonia-Borane Catalyzed by Porphyrin Stabilized Nanocatalysts

Article abstract of DOI:10.1007/s10562-020-03501-8

Abstract: Ammonia-borane (AB) is one of the most promising fuel forms for the hydrogen economy, but the reaction requires a good catalyst to accelerate this hydrolysis reaction under ambient conditions. Here, H₂ evolution upon hydrolysis of amm

Full text of DOI:10.1007/s10562-020-03501-8

Catalysis Letters
https://doi.org/10.1007/s10562-020-03501-8
H2 Evolution Upon Hydrolysis of Ammonia‑Borane Catalyzed
by Porphyrin Stabilized Nanocatalysts
Nuonuo Zhang1 · Genjiang Liu1 · Yao Sun1 · Yanlan Wang2 · Jiaying Yan1 · Xiang Liu1
Received: 2 September 2020 / Accepted: 14 December 2020
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature 2021
Abstract
Ammonia-borane (AB) is one of the most promising fuel forms for the hydrogen economy, but the reaction requires a good
catalyst to accelerate this hydrolysis reaction under ambient conditions. Here, H2 evolution upon hydrolysis of ammonia-
borane catalyzed by tetra-(p-hydroxyphenyl) porphyrin (THPP) stabilized transition metal nanoparticles (RhNPs/THPP,
RuNPs/THPP, PtNPs/THPP) has been reported for the frst time. The as-synthesized nanocomposites (TMNPs/THPP) show
high catalytic activity in the AB hydrolysis. Among these TMNPs/THPP, the RhNP-3/THPP exhibits the best catalytic activ-
ity with a TOF of 213.64 molH2 molcata−1 min−1. In addition, tandem reaction for 1,1-diphenylethylene hydrogenation has
also confrmed the H2 evolution upon hydrolysis of ammonia-borane.
Graphic Abstract
Keywords Hydrogen · Nanoparticles · Ammonia-borane · Porphyrin
Supplementary Information The online version contains
supplementary material available at https://doi.org/10.1007/s1056
2-020-03501-8.
* Jiaying Yan
yanjiaying327@126.com
Conversion; Analysis and Testing Center, China Three
Gorges University, Yichang 443002, Hubei, China
2
* Xiang Liu
xiang.liu@ctgu.edu.cn
College of Chemistry and Chemical Engineering, Liaocheng
University, Liaocheng 252059, Shandong, China
1
College of Materials and Chemical Engineering, Key
Laboratory of Inorganic Nonmetallic Crystalline and Energy
Vol.:(0123456789)
1 3

N. Zhang et al.
cell imaging due to its marvelous photocatalytic properties,
optical and chemical properties. A long term endeavor has
been devoted to the synthesis of porphyrins, their precursors,
and their applications [28–38]. In our previous work [39],
porphyrins have been used as support in catalysis because
they often exert the function of multiple binding sites (N, O)
contributing to protect metal NPs and inhibit their aggrega-
tion. It is noteworthy, however, that the reports on the usage
of porphyrins as NP supports in hydrogen generation are rare
in the hydrolysis of AB.
1 Introduction
Fossil energy has been the main energy resource in the word,
but hazardous solid and gas such as CO, NOx, SO2, SO3, H2S
were always generated in their usage. It’s urgent to explore
sustainable and clean energy and its carrier instead of fossil
energy in the last two decades [1, 2]. The development of
hydrogen and its storage materials that would be applied in
automotive applications is an increasing worldwide demand
[3, 4]. Among all hydrogen-storage materials, ammonia-
borane (NH3BH3, denoted as AB) as a source of hydrogen
and clean energy carrier is water-soluble, nontoxic, high
hydrogen content (ca. 19.6 wt%) and highly stable in solid
and solution states under ambient conditions [5–9]. The
hydrolysis of AB is an efcient and feasible reaction in the
presence of catalyst, which was broadly used instead of
thermolysis reaction requiring high temperature. In the AB
hydrolysis process, one mole of AB could generate three
moles of hydrogen completely.
Here we report the synthesis, characterization, and
employment of tetra-(p-hydroxyphenyl) porphyrin (THPP)-
stabilized Rh-, Ru-, and PtNPs as highly active homogene-
ous catalyst in hydrogen evolution from the hydrolysis of
AB for the frst time (Scheme 1). THPP-stabilized TMNPs
were prepared from the reduction of metal ion by NaBH4
in the presence of THPP. We then highlight the efciency
of RhNPs/THPP nanocatalyst by comparing the catalytic
activities of Ru, PtNPs/THPP catalysts in the hydrolysis of
AB under mild conditions. Subsequently, we scrutinize the
catalytic behavior of RhNPs/THPP nanocatalysts for the
hydrolysis of AB in EtOH/water (v/v, 4:1). The catalytic
activity of the nanocatalyst RhNP-3/THPP with a TOF value
of 213.64 molH2 molcata−1 min−1 is higher than Ru, PtNPs/
THPP catalysts for the AB hydrolysis. In addition, tandem
reaction for diphenylacetylene hydrogenation has also con-
frmed the H2 evolution upon hydrolysis of ammonia-borane.
NH3BH3 + 4H2O → NH4B(OH)4 + 3H2(g)
(1)
Until now, efective nano-catalysts (<5 nm) for hydroly-
sis of AB are typically expensive and rare noble metal nano-
particles (NPs), such as Rh, Pt, and Ru. In order to design
high-performance noble metal nano-catalysts, considerable
eforts have been devoted to synthesis of metal NPs sta-
bilized by supports [10–17]. Supported NP catalysts have
exhibited catalytic efciencies dramatically. Meanwhile, it
has also been found that NP supports signifcantly infuenced
and/or eventually determined the catalytic activities [18–22].
In this regard, many supports have been developed for
stabilizing transition metal nanoparticles (TMNPs), such as
dendrimers, polymers, soft balls, metal–organic frameworks
(MOFs), graphene quantum dots and porphyrins [23–27].
Porphyrins as macrocycle organic compounds exhibit tre-
mendous applications in the feld of catalysis, photody-
namic and photothermal therapy, antimicrobial material,
2 Results and Discussion
Tetra-(p-hydroxyphenyl) porphyrin (THPP) has been
prepared easily by classical Alder reaction of p-hydroxy-
benzaldehyde and pyrrole in a mixture of propionic acid/
dimethylsulfoxide under refux for 2 h [40]. In our previ-
ous work [39], THPP has been successfully synthesized.
Nano-catalysts RhNP-1–3/THPP were prepared by using
THPP and rhodium nitrate in a molar ratio 1:1, 1:2 or 1:4 of
Scheme 1 AB hydrolysis cata-
OH
lyzed by TMNPs/THPP
HO
N
N
H
OH
N
HN
OH
OH
OH
Rh(NO3)3, RuCl3,
NH
NHN
N
HO
OH
HO
PtCl4
NH
N
N
NH
NHN
N
OH
HO
OH
HO
OH
TMNPs/THPP
HN
NaBH4
OH
OH
HO
OH
OH
NHN
NHN
OH
THPP
NH3BH3 + 4H2O
NH4+ + B(OH)4- + 3H2
1 3

H2 Evolution Upon Hydrolysis of Ammonia-Borane Catalyzed by Porphyrin Stabilized…
porphyrin/metal ion which was dissolved in the mixture of
EtOH/water (8 mL/2 mL, v/v, 4:1) under ice bath. Subse-
quently, NaBH4 as a reductant was added. Rh (III) ions was
reduced to RhNP which was stabilized with N or O-atoms in
the structure of porphyrin. The corresponding nano-catalysts
with a small size was obtained. However, the characteristic
peaks of RhNPs did not appear in the UV–Vis spectra due to
their small size. Then, the AB dehydrogenation was carried
out using RhNP/THPP nano-catalysts to study the best molar
ratio of porphyrin/metal ion at room temperature.
All the RhNP-1–3/THPP used as catalysts for AB hydrol-
ysis are based on those already reported literature [41, 42].
The catalytic performances of various RhNPs/THPP evalu-
ated for the catalytic hydrolysis of AB are shown in Fig. S1,
and RhNP-3/THPP with molar ratio 1:4 of porphyrin/metal
ion presents the best performance. With this RhNP-3/
THPP catalyst, the stoichiometric amount of H2 (3 mol H2
per mol AB) is obtained after 4 min with a TOF value of
149.55 molH2 molcata−1 min−1, followed by RhNP-2/THPP
(TOF=135.95 molH2 molcata−1 min−1), and RhNP-1/THPP
(TOF=46.87 molH2 molcata−1 min−1). Thus, it demonstrated
that the molar ratio 1:4 of porphyrin/metal ion is the best
catalyst (Fig. S1). The ICP measurement was also carried
out for RhNP-3/THPP with 35% load rate (calculated value
is 37%). Then, RuNP/THPP and PtNP/THPP have been syn-
thesized as the molar ratio 1:4 of porphyrin/metal ion under
the same conditions as for RhNP-3/THPP. UV–Vis spectra
of THPP, TMNPs/THPP were showed in Figs. S2–7. Simi-
larly, RuNP has not any characteristic peaks in the UV–Vis
spectra (Fig. S7). As shown in Fig. 1, TEM illustrated the
size of the RhNP-3/THPP is 2.53 nm (Figs. 1a and S8),
RuNP/THPP is 2.56 nm (Figs. 1b and S9) and PtNP/THPP
is 2.14 nm (Figa. 1c and S10), respectively.
X-ray photoelectron spectroscopy (XPS) has also been
measured to explore the chemical states of Rh, Ru, Pt in
the RhNP-3/THPP, RuNP/THPP and PtNP/THPP. Fig-
Fig. 1 TEM images of the RhNP-3/THPP (a), RuNP/THPP (b),
ure 2a shows that only Rh(0) exhibits on the surface of the
RhNP-3/THPP. And the peaks located around 309.70 eV and
314.41 eV are attributed to Rh 3d5/2 and Rh 3d3/2, respec-
tively [41, 43]. Particularly, the binding energy of Rh 3d
is shifted. The change has been caused by the infuence
between THPP and metal atoms. Figure 2b illustrated the
peaks of Ru 3d exhibiting at 282.19 eV and 286.39 eV. The
binding energy of 282.19 eV and 286.39 eV are assigned to
Ru 3d5/2, Ru 3d3/2 [44, 45]. The results indicated that Ru3+
ions have been reduced to zero-valent Ru on the surface.
Similarly, the XPS of Pt also shows that the Pt(0) 4f peaks
appear at 72.58 eV and 75.91 eV (Fig. 2c), which corre-
spond to 4f7/2 and 4f5/2, respectively [46, 47]. Figure 3 shows
the catalytic AB hydrolysis process under the presence of
0.8 mmol% TMNP/THPP at 30 ℃. It indicated that the high-
est catalytic activity in hydrolysis of AB is RhNP-3/THPP
based on the plot of H2 generated versus time under the same
PtNP/THPP (c)
condition during the reaction. The activity of RuNPs/THPP
and PtNPs/THPP are lower than RhNPs-3/THPP.
The present catalytic system gave an excellent TOF
value of 213.64 molH2 molcata−1 min−1, followed by RuNPs/
−1
THPP (TOF = 83.3 molH2 molcata min−1), and PtNP/
THPP (TOF=53.6 molH2 molcata−1 min−1). Then hydroly-
sis of AB catalyzed by various RhNPs (0.20, 0.40, 0.60,
0.80 mol%) stabilized by THPP was carried out at 30 °C.
As shown in Fig. 4, hydrogen generation enhanced with
the increase of the catalyst amount in the TOF value order
213.64 (0.80 mmol%) > 166.17 (0.60 mmol%) > 149.55
.
(0.40 mmol%) > 131.80 molH2 molcata−1·min−1
(0.20 mmol%). Moreover, the slope of logarithmic plot
in Fig. 4b is 1.17. It means that the hydrolysis reaction is
1 3

N. Zhang et al.
Fig. 2 XPS spectrum of RhNP-3/THPP (a), RuNP/THPP (b) and PtNP/THPP (c)
frst order in the catalytic amounts. As shown in Fig. 5, it is
accelerated for hydrogen generation as the enhancement of
the AB concentration. Moreover, the slope of logarithmic
plot is 0.29 in Fig. 5b, suggesting the hydrolysis reaction is
frst order in AB concentration.
To study the hydrolysis mechanism, this hydrolysis reac-
tion catalyzed by TMNPs/THPP was studied under vari-
ous temperatures. The catalytic activity of RhNP-3/THPP
at diferent temperatures ranging from 303 to 323 K was
also studied in hydrogen generation. As shown in Fig. 6a,
the efciency of AB hydrolysis enhances when the reaction
temperature rises from 303 to 323 K. An unanticipated TOF
value of 900 molH2 molcata−1 min−1 was achieved at 323 K.
From the Fig. 6b, the activation energy (Ea) is 56.56 kJ/mol
which is calculated based on the Arrhenius equation Eq. (2)
involved in the reaction rate (k), the pre-exponential factor
Fig. 3 Catalytic efciencies of the AB hydrolysis catalyzed by
TMNPs/THPP
Fig. 4 a Plots of catalytic efciencies in the presence of various catalytic amounts; b plots of H2 evolution rate versus the catalytic amounts both
on natural logarithmic scales
1 3

H2 Evolution Upon Hydrolysis of Ammonia-Borane Catalyzed by Porphyrin Stabilized…
Fig. 5 Plots of H2 versus time for the AB hydrolysis catalyzed by the 0.8 mmol/L RhNPs-3/THPP (4 × 10–3 mmol Rh) at diferent AB concen-
tration (a), and plots of H2 generation rate versus the AB concentration both on natural logarithmic scale (b)
Fig. 6 a Catalytic efciencies of the AB hydrolysis catalyzed by the 0.4 mmol% RhNPs/THPP at diferent temperature; b the kinetic image both
on natural logarithmic scales
(A), the gas constant (R, 8.314 J mol−1 K−1) and the reaction
temperature (T (K)).
at the ffth run. Compared to the TOF value of 41.67
molH2 molcata−1 min−1 at the frst run, the decline in cata-
+
Cycle experiments have also been carried out to testify
its catalytic reusability of RhNP-3/THPP in this hydrogen
evolution from aqueous AB. Figure S11 shows the genera-
tion of equivalent H2 per 0.5 mol of AB versus time from
the 1st to 5th use of RhNP-3/THPP (0.4 mmol% Rh) under
lytic activity could be owing to the accumulation of NH4
and B(OH)4− product adsorbed on the NP surface.
For further confirming the H2 evolution upon the
hydrolysis of AB, tandem reaction was carried out for the
1,1-diphenylethylene hydrogenation (Eq. 3) with H2 gen-
erated from AB hydrolysis (Fig. S13). The result exhib-
its that the desired product of ethane-1,1-diyldibenzene
is provided in 99% yield, confrming the evolution of H2
(Fig. S14).
(
)
Ea
Ln k = Ln A − −
(2)
RT
303 K. Surprisingly, catalytic activity of RhNP-3/THPP
−1
still exhibits a TOF value of 35.7 molH2 molcata min−1
1 3

N. Zhang et al.
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3 Conclusion
In summary, highly dispersed tetra-(p-hydroxyphenyl) por-
phyrin (THPP)-stabilized RhNPs, RuNPs, and PtNPs have
been successfully synthesized for H2 evolution upon hydrol-
ysis of ammonia-borane for the frst time. TEM images
exhibit that the average sizes of RhNP-3/THPP, PtNP/THPP
and RuNP/THPP are 2.53, 2.14 and 2.56 nm, respectively.
The TOF value of RhNP-3/THPP reaches the excellent
value of 213.64 molH2 molcata−1 min−1 for production of H2
completed in 1.75 min at 30 ℃. The catalyst also shows
good durability and cyclicity under the ambient condition.
The excellent catalyst RhNP-3/THPP shows that activity of
catalyst is still retained after fve cycles. We found the acti-
vation energy (Ea) is 56.56 kJ/mol for H2 evolution, based
on the Arrhenius equation. In addition, tandem reaction for
1,1-diphenylethylene hydrogenation has also confrmed the
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Acknowledgements Financial support from the National Natural
Science Foundation of China (Nos. 21606145, 21805166), the 111
Project (No. D20015), State Key Laboratory of Coordination Chem-
istry Foundation of Nanjing University (No. SKLCC1811), the Engi-
neering Research Center of Eco-environment in Three Gorges Reser-
voir Region, Ministry of Education, China Three Gorges University
(KF2019-05) and the outstanding young and middle-aged science and
technology innovation teams, Ministry of Education, Hubei province,
China (T2020004) and China Three Gorges University is gratefully
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