Hierarchically structured rugae-like RuP3-CoP arrays as robust catalysts synergistically promoting hydrogen generation

Article abstract of DOI:10.1039/c8ta10695a

Designing a highly active and stable catalyst for NaBH₄ hydrolysis is a key step towards overcoming the challenges of hydrogen storage. Herein, we have developed a controllable strategy to fabricate a series of hierarchically structured cobalt-ruthenium-phosphide arrays on nickel foam (Co-Ru-P@NF) as a highly efficient and stable catalyst for hydrogen generation from NaBH₄ hydrolysis in alkaline media. SEM and TEM analyses show that the interconnected rugae-like Co-Ru-P arrays are vertically grown on the surface of Ni foam, together with uniformly distributed RuP₃ nanoclusters on the surface of CoP nanosheets. More importantly, the optimized Co-Ru-P@NF catalyst exhibits an outstanding catalytic performance on NaBH₄ hydrolysis in alkaline media with a high turnover frequency (TOF) of 2123.6 mol_H2 min^-1 mol_Ru^-1 at 25 °C, which is one of the highest known so far. Furthermore, the exceptional catalytic performance is in line with the outcome of low activation energy (40.3 kJ mol^-1). Additionally, the catalyst also shows a high stability with less than 8.0% lost after 5 consecutive cycles. The superior catalytic performance is ascribed to the synergetic effect between RuP₃ and CoP species resulting in a significant electron transfer effect, together with the unique morphologies associated with a large specific surface area and open-channels for effective solute transport/adsorption and H₂ gas emissions.

Full text of DOI:10.1039/c8ta10695a

View Article Online
View Journal
Journal of
Materials Chemistry A
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: J. Guo, C. Wu, J.
Zhang, P. Yan, J. Tian, T. Taylor Isimjan and X. Yang, J. Mater. Chem. A, 2019, DOI: 10.1039/C8TA10695A.
This is an Accepted Manuscript, which has been through the
Volume
4 Number 1 7 January 2016 Pages 1–330
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry A
Accepted Manuscripts are published online shortly after
Materials for energy and sustainability
www.rsc.org/MaterialsA
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 2050-7488
PAPER
Kun Chang, Zhaorong Chang et al.
Bubble-template-assisted synthesis of hollow fullerene-like
MoS2 nanocages as a lithium ion battery anode material
rsc.li/materials-a

Page 1 of 19
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C8TA10695A
1
2
3
Hierarchically Structured Rague-Like RuP3-CoP Arrays
as Robust Catalyst Synergistically Promoting Hydrogen
Generation
4
5
Jingya Guo,† Chongbei Wu,† Jifang Zhang,† Puxuan Yan,† Jianniao Tian,† Tayirjan Taylor
Isimjan,*,‡ Xiulin Yang*,†
6
7
8
†Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources
(Ministry of Education of China), College of Chemistry and Pharmacy, Guangxi Normal
University, Guilin 541004, People’s Republic of China
9
‡Saudi Arabia Basic Industries on (SABIC) at King Abdullah University of Science and
Technology (KAUST)
10
11
E-mail: xiulin.yang@kaust.edu.sa; isimjant@sabic.com
12
13
14
15
1

Journal of Materials Chemistry A
Page 2 of 19
View Article Online
DOI: 10.1039/C8TA10695A
1
2
Abstract
Designing a highly active and stable catalyst for NaBH4 hydrolysis is a key step towards
overcoming the challenges of hydrogen storage. Herein, we have developed a controllable
strategy to fabricate a series of hierarchically structured cobalt-ruthenium-phosphide arrays on
nickel foam (Co-Ru-P@NF) as a highly efficient and stable catalyst for hydrogen generation
from NaBH4 hydrolysis in alkaline media. SEM and TEM analyses show that the
interconnected rague-like Co-Ru-P arrays are vertically grown on the surface of Ni foam,
together with uniformly distributed RuP3 nanoclusters on the surface of CoP nanosheet. More
importantly, the optimized Co-Ru-P@NF catalyst exhibits an outstanding catalytic
performance on NaBH4 hydrolysis in alkaline media with a high turnover frequency (TOF) of
2123.6 molH2 min-1 molRu-1 at 25 °C, which is one of the highest known so far. Furthermore,
the exceptional catalytic performance is in line with the outcome of the low activation energy
(40.3 kJ mol-1). Additionally, the catalyst also shows a high stability with less than 8.0% lost
after 5 consecutive cycles. The superior catalytic performance is ascribed to the synergetic
effect between RuP3 and CoP species resulting in a significant electron transfer effect, together
with the unique morphologies associated to a large specific surface area and open-channels for
effective solute transport/adsorption and H2 gas emissions.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
Keywords: CoP nanosheet; RuP3 nanoclusters; Synergistic effect; NaBH4 hydrolysis;
Hydrogen generation
2

Page 3 of 19
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C8TA10695A
1
2
1. Introduction
Dealing with the continuously growing energy demand resulting from the fossil fuel depletion
and a related environmental crisis is prompting vigorous research on the field of clean and
sustainable alternative energy sources.1-3 Molecule hydrogen with the highest gravimetric
energy density (120 MJ/kg) is regarded as a promising candidate.4-6 However, H2 storage and
transportation are two main hindrances to launch a H2 economy.7-9 The H2 can be stored both
in physical and chemical methods where the H2 either is adsorbed on highly porous materials
such as MOFs and porous carbon which requires extremely low temperature or stored as metal-
hydride complexes including boron hydrides (NaBH4, NH3BH3 and LiBH4) which has the
advantages of high H2 content (10∼20%), high water solubility and stability at room
temperature as well as non-toxicity.10-12 Nevertheless, the boron hydrides hydrolysis generally
suffer from sluggish kinetics.13 Therefore, developing a low cost and high-performance catalyst
become an essential step to promote the H2 storage through boron hydrides. Although the noble
metal catalysts such as such as Pt/CeO2-Co7Ni2Ox,14 Pd/PD-ZIF-67,15 Pt/3D SiC,16 Pt58Ni33Au9,17
Pt/mesoporous silica,18 Ru@SiO2,19 Ni-Ru,20 Rh/Ni BNPs,21 Co0.8-Ag0.2-B,22 etc. exhibit the
high catalytic performances, they also limited by the cost. As a result, developing the transition
metal (Co, Fe, and Ni) based catalysts become the main focus on boron hydride hydrolysis.
The recent studies reveal a significant enhancement in the catalytic performance of the
transition metal catalyst by incorporating foreign elements including B and P.23-26 The
improvement of the catalytic performance could be due to electron transfer from B or P to the
vacant d-orbital of the metal and the electron enriched metal sites further donate the electrons
to the surface attached hydrogen atoms thereby accelerates detachment of the surface adsorbed
hydrogen atoms.27 Furthermore, for metal phosphate, in particular, introducing additional
foreign metals can further increase the catalytic performance.28, 29 However, the actual catalytic
performance is largely altered by the catalyst preparations, microstructure engineering, surface
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
3

Journal of Materials Chemistry A
Page 4 of 19
View Article Online
1
2
area, and the catalyst support. In general, the porous supports such as nickel foam (NF), copper
DOI: 10.1039/C8TA10695A
foam, titanium sheet, porous carbon, Al2O3, SiO2, TiO2 not only supply high surface area but
also inhabit the catalyst aggregation thereby improve both activity and stability.30-33 Compare
to powder catalyst, the metal sheet supported catalysts can be easily separated from the solution
and used as on/off switch for on-demand hydrogen production.34 Liu and co-workers found
that CoP nanowire array integrated on Ti mesh showed a high hydrogen generation rate for
hydrolytic dehydrogenation of NaBH4 in alkaline solutions.34 Moreover, Sun and co-workers
also reported that the Fe-doped CoP nanoarray on Ti foil exhibited high hydrogen generation
rate and low activation energy for hydrolytic dehydrogenation of NaBH4 in basic media.29
Recently, NF support attracted a lot of attention due to the distinguished features such as three-
dimensional reticular configuration, high surface area, high flexibility and low cost.8, 35
Herein, we have developed a facile and controllable strategy to synthesize a novel RuP3
coated CoP on NF hybrid catalyst where the cheapest noble metal Ru36 was used in a small
quantity in order to minimize the cost. X-ray diffraction patterns indicate that the RuP3 and
CoP species are formed, and the contents of Ru and Co in the optimized catalyst are indicated
to be Co0.991Ru0.09P by ICP-AES. SEM and TEM demonstrate that rague-like CoP arrays are
grown on the skeleton of NF, and RuP3 nanoclusters are uniformly dispersed on the CoP
nanosheet surface. The optimized Co-Ru-P@NF catalyst exhibits an outstanding catalytic
performance and high stability for NaBH4 hydrolysis. This exceptional performance can be
ascribed to the synergetic effect of RuP3 and CoP species, along with the unique morphologies
and high surface area offered by NF. Furthermore, a catalytic mechanism of NaBH4 hydrolysis
on the Co-Ru-P@NF hybrid catalyst was purposed.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
2. Experimental section
2.1. Synthesis of Co-species@NF
4

Page 5 of 19
Journal of Materials Chemistry A
View Article Online
1
2
Co-species nanosheet arrays on NF (Ni foam) was prepared as follows, wherDeOaI: 1p0.i1e0c39e/Co8fTA10695A
NF (1 cm×1 cm×1.6 mm) was carefully pretreated in 1.0 M HCl, deionized water and ethanol
for 5 min respectively. It was then repeated three times to confirm that the surface of NF was
well cleaned.
3
4
5
To prepare the Co-species@NF, 1.0 mmol of Co(NO3)2⋅6H2O was ultrasonically dissolved
in 40 mL deionized water to form a uniform solution. The electrodeposition experiments were
carried out at room temperature in a standard three-electrode system with NF as the working
electrode, a Pt sheet as the counter electrode, and a standard SCE as the reference electrode.
The applied current density was set as −10 mA cm-2, and different electrodeposition times were
conducted to control the amount of the Co-species (20, 30, 40, 50 and 60 min). The resulted
samples were washed by abundant deionized water and dried in air at room temperature. The
loadings of Co-species on NF surface are calculated for 3.67, 5.5, 7.34, 9.17 and 11.01 mg cm-
2, respectively.
6
7
8
9
10
11
12
13
14
15
16
17
18
19
2.2. Synthesis of CoRu-species@NF
50 mg of ruthenium(III) 2,4-pentanedionate was ultrasonically dispersed into 10 ml ethanol
to form a homogeneous solution. Then, the mixture solution was pipetted onto the surface of
Co-species@NF-60 and dried in air at room temperature. For a better comparison, different
volumes of the precursors on the NF-60 surface are investigated. Moreover, the precursor
covered fresh NF is also studied.
20
21
22
23
24
2.3. Synthesis of Co-Ru-P@NF by vapor phase phosphidation
The phosphidation process was performed in a tube furnace, where the NaH2PO2 in a
porcelain boat was put in the upstream side and a series of CoRu-species/NF samples were
placed next to the NaH2PO2 at a downstream side. The furnace was heated to 350 °C with 2 °C
min-1 in Ar atmosphere (20 sccm), and kept at 350 °C for 2 h. After the phosphidation, the
5

Journal of Materials Chemistry A
Page 6 of 19
View Article Online
1
2
samples were cooled down to ambient temperature in flowing Ar gas. As a comDpOaIr: i1s0o.10n3,9/tCh8eTA10695A
CoP@NF, RuP3@NF and Ni2P@NF were also prepared by a similar phosphidation process.
3
4
2.4. Catalyst characterizations
The crystal structures of catalysts were analyzed by X-ray powder diffraction (XRD,
Rigaku D/Max 2500 V/PC) with a sweep speed for 2.0 degree min-1. The morphologies and
microstructures of the catalysts were characterized by scanning electron microscope (SEM,
FEI Quanta 200 FEG) and transmission electron microscope (TEM, JEM-2100F). The X-ray
photoelectron spectrometer (XPS, JPS-9010 Mg Kα) was used to analyze the chemical states
of different elements. The specific surface area of the as-prepared product was measured on a
Quantachrome Autosorb AS-1 instrument. The actual loadings of different metals in the
catalyst were checked by inductive coupled plasma atomic emission spectroscopy (ICP-AES,
IRIS Intrepid II XSP).
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
2.5. Catalytic measurements
The catalytic activity, cycle stability and activation energy of the catalytic material were
obtained by the following methods. Typically, 50 mL mixture solution (contained 150 mM
NaBH4+0.4 wt% NaOH) was kept in a three-necked round-bottom flask (100 mL), which was
placed in a water bath at 25 °C. The volume of H2 was monitored by a drainage which was
connected to a computer to record the instantly changed qualities of water. The catalytic
reaction was started when the catalyst was added into the flask under constant magnetic stirring
conditions. In order to test the recyclability of the catalyst, we continued to use the fresh NaBH4
21
22
23
24
25
solution instead of the fully decomposed NaBH4 solution for five consecutive cycles at 25 °C.
After each stability test, we centrifuged the catalytic material, dried it under vacuum condition
at room temperature, and weighed the catalytic material. All experiments were repeated three
times to ensure the reliable results. The activation energy of the designed catalyst was evaluated
in the same device in the temperature range of 25 to 45 °C.
6

Page 7 of 19
Journal of Materials Chemistry A
View Article Online
1
2
The specific H2 generation rate (HGR) and turnover frequency (TOF) values iDsOcI:a1l0c.1u03la9/tCe8dTA10695A
as follows,34, 37
ꢃ
(ꢆꢇ)
ꢅ
ꢄ
2
3
4
ꢀꢁꢂ =
ꢊꢋꢌ =
(1)
(2)
(
)
ꢈ min × ꢆ (ꢉ)
ꢍ
(ꢆꢎꢏ)
ꢄ
2
(
)
ꢈ min × ꢍ (mol)
ꢐꢑ
5
6
7
where VH2O is the volume of drained water, m is the total mass of the catalyst, nH2 is the moles
of generated H2, nRu is the moles of Ru in the catalyst, and t is the total reaction time in
minutes.
8
9
3. Results and discussion
3.1. Synthetic strategy analysis
C16H21O8Ru
Phosphorization
Co(NO3)2
Electro-deposition
Dropwise
Ar, 350 °C, 2h
Electrochemical system
Co-species@NF
CoRu-species@NF
Co-Ru-P@NF
10
11
Fig. 1. Schematic diagram of the formation of Co-Ru-P@NF catalyst.
12
13
14
15
16
17
18
19
20
The three dimension Co-Ru-P@NF catalysts were prepared through three steps including
electrodeposition of Co species, Ru modification and high-temperature phosphorization (Fig.
1). Initially, the Co-species were loaded on NF surface (Co@NF) by electrodeposition at a
constant current density within various time lengths. Thereafter, Ru-precursors in ethanol
solution were loaded dropwise onto the surface of Co@NF. Finally, the Ru loaded Co@NFs
were placed in a porcelain boat next to another porcelain boat in the upside containing
NaH2PO2 as phosphor sources. The hierarchically structured Co-Ru-P@NF materials were
prepared through a vapor deposition of phosphorous under constant argon flow at 350 °C for 2
7

Journal of Materials Chemistry A
Page 8 of 19
View Article Online
1
2
3
4
5
h. The metal loadings were determined by ICP-AES, which were used to calculate the TOF of
DOI: 10.1039/C8TA10695A
H2 generation (Table S1). Moreover, the pictures of the sample at different stages indicate the
surface transformations by various chemical treatments as shown in Fig. S1 and the weight
changes of the catalysts were monitored using a precision balance to calculate the following
H2 generation rates (Table S2).
6
3.2. Crystal structures and microstructures analysis
a
c
b
5 μm
100 μm
e
d
f
2 μm
2 μm
2 μm
100 μm
100 μm
100 μm
7
8
Fig. 2. X-ray diffraction (XRD) patterns of (a) CoP@NF and Co-Ru-P@NF along with (b)
RuP3. Scanning electron microscopy (SEM) images of (c) NF, (d) Co-species@NF, (e)
CoP@NF and (f) Co-Ru-P@NF. The inserts are the magnified SEM images.
9
10
11
12
13
14
15
The crystal structures of as-prepared materials are initially investigated by XRD patterns.
As shown in Fig. S2a, the electrodeposited Co-species on NF surface are consistent with the
standard XRD features of Co(OH)2 (JCPDS: 30-0443).38 After phosphorization process, the
color of Co@NF changed from dark blue to black. The cobalt phosphate species mainly
8

Page 9 of 19
Journal of Materials Chemistry A
1
2
consists of CoP (JCPDS: 65-2593)39 and a trace of Co2P species (JCPDS: 54-0413D),OwI: 1h0.e10r3Ve9ie/wtChA8erTtiAcl1e0O6n9li5nAe
XRD patterns of the Ru species cannot be detected due to the low Ru loading as shown in Fig.
2a. However, the pure Ru-species which were synthesized by similar conditions were detected
by the XRD pattern in Fig. 2b and the patterns are consistent with RuP3 (JCPDS: 78-1268). In
addition, the NF was phosphatized and used as a control sample. Small amounts of Ni2P species
(JCPDS: 03-0953) formed on the NF surface (Fig. S2b). Moreover, none of the diffraction
peaks of NF and Ni2P appeared on Co modified NF indicating a full surface coverage of NF.
Therefore, the contribution of Ni2P towards the catalytic performance of RuP3-CoP is
negligible. As shown in Fig. 2c, the SEM images are used to distinguish the morphological
changes of NF before and after deposition. The surface morphology of NF changes
dramatically from the relatively smooth surface to highly ring coiled hierarchical structures in
micro level after different electrodeposition times, indicating the formation of Co(OH)2
nanosheets on NF surface which becomes denser upon increase of the deposition time (Fig. S3,
Fig. 2d). After phosphorization at 350 oC, the vertically oriented hierarchical structure starts to
shrink because of the crystal structure transformation from amorphous to crystalline. The
similar phenomena are observed on both CoP@NF and Co-Ru-P@NF (Fig. 2e and 2f). The
hierarchical structures not only provide the high surface area thereby promoting a better mass
transfer but also exposes more active sites. Therefore, a high catalytic performance is expected.
Moreover, the N2 adsorption–desorption isotherms at 77 K of Co-Ru-P@NF catalysts with
different loadings of Ru species were used to investigate the Brunauer−Emmett−Teller (BET)
surface area. The results revealed that when the loading of Ru in the Co-Ru-P@NF is 0.197
mg cm-2, the BET surface area is 11.4 m2 g-1, and when the loading of Ru is 0.455 mg cm-2, the
BET surface area is 13.3 m2 g-1 (Fig. S4).
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
9

Journal of Materials Chemistry A
Page 10 of 19
View Article Online
a
DOI: 10.1039/C8TA10695A
b
0.28 nm
(011)
CoP
RuP3
0.25 nm
(002)
0.39 nm
(110)
50 nm
2 nm
2 nm
1
2
Fig. 3. (a) Transmission electron microscopy (TEM) and (b) high-resolution TEM images of
Co-Ru-P material. The inset of Fig. 3a represents the particle size distribution of RuP3. (c)
Typical TEM image of Co-Ru-P and the corresponding Ru, Co and P elemental mappings.
3
4
5
6
To further examine the microscopic features of the Co-Ru-P@NF, detailed TEM studies
were undertaken. As shown in Fig. 3a, the RuP3 nanoclusters with an average particle size of
2.6 nm are uniformly dispersed on the surface of CoP nanosheet. The crystal structures of both
CoP and RuP3 are confirmed in Fig. 3b where the distinct lattice fringe with a spacing of 0.28
nm is corresponding to the (111) plane of CoP, and the two closely related spacings of 0.25
and 0.39 nm are attributed to the (002) and (110) planes of RuP3, respectively. Furthermore,
the HAADF-STEM (Fig. 3c) and corresponding elemental mapping images reveal the
homogenous distribution of Ru, Co, and P in the Co-Ru-P nanostructures. Notably, the much
sparser Ru dispersion patterns are consistent with features the low content Ru-based material
in the hybrid composite.
7
8
9
10
11
12
13
14
15
16
3.3. XPS analysis
10

Page 11 of 19
Journal of Materials Chemistry A
View Article Online
a
c
Co-Ru-P@NF
DOI: 10.1039/C8TA10695A
b
Co-Ru-P@NF
C-C
P-O
C 1s+Ru 3d
Co-Ru-P@NF
Co 2p
Co-P
P 2p
Co-O
Sat.
P-Co
P-Ru
P 2p1/2 P 2p3/2
C-O
Ru 3d3/2
Ru 3d5/2
C=O
RuP3@NF
CoP@NF
CoP@NF
0.23 eV
292 290 288 286 284 282 280 278
Binding energy (eV)
810 805 800 795 790 785 780 775
Binding energy (eV)
140 138 136 134 132 130 128 126
Binding energy (eV)
1
2
Fig. 4. High-resolution X-ray photoelectron spectroscopy (XPS) of (a) C 1s + Ru 3d, (b) Co
3
4
2p and (c) P 2p regions from Co-Ru-P@NF, RuP3@NF and CoP@NF.
5
The chemical states of each elements in Co-Ru-P@NF are further analyzed by XPS, where
the Ni cannot be detected on the surface of the Co-Ru-P@NF (Fig. S5), which not only shows
a uniform deposition of Co but also indicates the Co film is thicker that the penetration depth
of XPS (around 10 nm). The high-resolution XPS spectra of C 1s + Ru 3d regions (Fig. 4a) are
convoluted into C-C (284.8 eV) and C-O (286.0 eV) used as a calibration standard,40, 41 as well
as the Ru 3d core level from RuP3 are convoluted at the binding energies of 280.8 eV (Ru 3d5/2)
and 285.0 eV (Ru 3d3/2).42 As shown in Fig. 4b, three peaks in the Co 2p3/2 regions at 778.3,
782.0 and 785.5 eV can be ascribed to the Co-P, Co-O and satellite peaks, respectively.43 In
addition, the high-resolution XPS spectrum of P 2p core level shows three types of peaks,
where a pair of peaks located at 129.1 eV (P 2p3/2) and 130.1 eV (P 2p1/2) are considered as P
2p in CoP.44 The another pair of peaks located at 129.7 eV (P 2p3/2) and 130.8 eV (P 2p1/2) are
attributed to P 2p in RuP3,45 along with a broad peak at 133.6 eV is assigned to phosphate
species.46 These distinct oxidation species peaks of Co-O and P-O can be explained by the
inevitable surface oxidation.47 We have compared the high-resolution Ru 3d XPS spectra of
RuP3@NF and Co-Ru-P@NF in Fig. 4a. The results show that the binding energy of Ru 3d of
6
7
8
9
10
11
12
13
14
15
16
17
18
19
11

Journal of Materials Chemistry A
Page 12 of 19
View Article Online
1
2
3
4
5
6
Co-Ru-P@NF exhibits a negative shift of ca. 0.23 eV compared to that of RuP3@NDFOiI:n1d0.i1c0a39t/iCn8gTA10695A
higher electron density on Ru in the Co-Ru-P@NF as compare to that of RuP3@NF due to the
partial electron transfer from Co species indicating that the electron density on Ru species is
lower than that of Co species. However, almost no shift was observed in the case of Co 2P
because Ru amounts are so small consequently the charge transfer is not significant enough to
cause the shift on Co 2P signal.
7
3.4. Catalytic hydrolysis analysis
a
b
200
150
100
50
CoP@NF
CoP@NF
2000
1500
1000
500
0
1920.6
1801.3 1803.1
1672.4
1312.9
20 min
30 min
40 min
50 min
60 min
0
0
200
400
600
800
20
30
40
50
60
Electrodeposition time (min)
Time (s)
c
d
200
150
100
50
2500
2000
1500
1000
500
Co-Ru-P@NF
Co-Ru-P@NF
2123.6
2000.6
Loading of Ru
-2
(mg cm )
1128.8
0.251
0.121
0.197
0.251
0.431
0.455
647.6
0.431
459.2
0.455
0
0
0
200
400
Time (s)
600
800
0.121
0.197
-2
Loading of Ru (mg cm )
8
9
Fig. 5. (a) The relationship between the H2 generation rates and electro-deposition times of
CoP@NF catalysts, and (b) the summarized TOF values. (c) The relationship between the H2
generation rates and loadings of Ru species on Co-Ru-P@NF catalysts, and (d) the summarized
TOF values. All the experiment are conducted in 150 mM NaBH4 + 0.4 wt % NaOH at 25 °C.
10
11
12
13
12

Page 13 of 19
Journal of Materials Chemistry A
View Article Online
1
2
The H2 production of NaBH4 hydrolysis using the designed catalysts were pDeOrfI:o1r0m.10e39d/Ci8nTA10695A
alkalized NaBH4 solution at 25 °C. The schematic illustration of the experimental setup is
shown in Fig. S6, where the amounts of the generated H2 was calculated according to the
weight of the water displaced by H2. The effect of electrodeposition of CoP at various time on
the H2 production was investigated in Fig. 5a-b. The results show that the H2 generation rate is
gradually increased with the prolonged deposition times and the 60 min deposition time was
selected as the basis of all the other experiments performed blow. In addition, the optimal Ru
loading was investigated by altering the deposition methods such as drop casting and dip
coating as well as the use of several Ru precursors including C15H21O6 Ru, RuCl2 and Ru
nanoparticles (Fig. S7). Then, the catalytic performance of the resulting catalysts on H2
generation was monitored (Fig. S8). Finally, the best catalytic performance was achieved by
using ethanol solution of C15H21O6Ru through drop casting method. The optimal loading is
around 0.2 mg (Ru)/cm2 measured by ICP-AES (Table S1-S2) and the overall Ru loading
against Co is around 1.57 wt% (0.09% mole%). The corresponding TOF to the fastest hydrogen
evolution rate (4840 mL min-1 g-1 catalyst) is 2123.6 mol min-1 molRu-1, which is the highest
TOF value reported so far among all the NaBH4 hydrolysis catalysts (Table S3). This
outstanding catalytic performance can be related to the high surface roughness that exposes
more active sites, uniform distribution of the active sites and synergic effect between Ru and
Co.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
To further evaluate this synergetic effect, a comparison study of NaBH4 decomposition was
performed between all the intermediate catalysts including CoP@NF, RuP3@NF, Co-
species@NF, Ni2P@NF and NF. The results show that the hydrogen generation rate of 1.57
wt% Ru loaded CoP@NF is significantly higher than that of CoP@NF and RuP3@NF (Fig.
S9). Meanwhile, the NF and Ni2P@NF show almost no activity towards H2 generation towards
NaBH4 hydrolysis (Fig. 6a). The specific H2 evolution rate of Co-Ru-P@NF is 4839.8 mL min-
13

Journal of Materials Chemistry A
Page 14 of 19
1 gcat-1 (total mass of catalyst), which are 2.52 and 23.55 folds higher than those of CoP@NF
DOI: 10.1039/C8TA10695A
View Article Online
1
2
3
4
5
6
7
8
9
and RuP3@NF respectively. To measure the activation energies, a set of experiments were
conducted at different temperatures using the two most active catalysts such as the Co-Ru-
P@NF and the CoP@NF. As shown in Fig. S10-S11, the rate of H2 generation increases rapidly
with increasing the reaction temperatures from 298 K to 318 K, and the rate constant κ is
calculated from the initial slope of each experiment. The activation energy of Co-Ru-P@NF
catalyst is calculated to be 40.3 kJ mol-1 by the Arrhenius plot (ln κ vs 1/T), which is much
lower than that of CoP@NF (56.1 kJ mol-1) (Fig. 6b), implying a kinetically enhanced catalytic
activity towards NaBH4 hydrolysis to produce H2 owing to the Ru.48
a
b
6.0
5.5
5.0
4.5
4.0
3.5
3.0
Co-Ru-P@NF
CoP@NF
5000 4839.8
E
=
40.
3 kJ m
a
4000
3000
2000
1000
0
-1
o
l
E
=
1920.6
a
56.
1 kJ m
-1
o
l
205.5
12.2
0.16
0.33
NF
F
NF
NF
@N
P3
Ru
NF
NF
@
3.10
3.15
3.20
3.25
-3 -1
3.30
3.35
3.40
P@
P@
Co
P@
Ni2
-
Co
Ru
-
Co
Catalyst
1/T(10 K )
10
11
Fig. 6. (a) The summarized TOF values of different catalysts for hydrolysis of 150 mM NaBH4
+ 0.4 wt % NaOH solution at 25 °C. (b) The summarized Arrhenius plots of CoP@NF and Co-
Ru-P@NF at different reaction temperatures for alkalized NaBH4 hydrolysis. (c) Recycling
stability test of the Co-Ru-P@NF catalyst in 150 mM NaBH4 + 0.4 wt % NaOH at 25 °C. (b)
12
13
14
14

Page 15 of 19
Journal of Materials Chemistry A
View Article Online
1
2
The specific H2 evolution rates and the corresponding TOF values of Co-Ru-P@NF catalyst in
DOI: 10.1039/C8TA10695A
the different recycling test.
3
4
The stability of the optimized Co-Ru-P@NF catalyst was evaluated by the continuous
recycling experiments of the NaBH4 hydrolysis in basic solution. The catalyst was cleaned,
freeze-dried and weighed after each cycle. The results show almost no changes in catalytic
performance after five consecutive cycles after normalizing to the catalyst-mass (Fig. 6c-d).
However, the time required to reach the 500 mL of H2 was increased from 5.9 to 13.9 min after
five cycles. The catalyst deactivation could be ascribed to the RuP3 exfoliation, structural
5
6
7
8
9
49
−
10
damages and catalyst poisoning by BO2 species (Fig. S12-S13).
11
3.5. Catalytic mechanism analysis
H
B
H
B
H
B
δ−
H
H
H
H
H
H
e−
H
H
H
Ⅱ
Ⅲ
Ⅰ
Co
Ru
P
O
OH
B
H
δ−
H
H
H
OH
H
OH
OH
OH
H
H
B
B
e−
H2
H
H
H2O
H2O
H2O
H2
Ⅴ
H2
Ⅵ
H2
Ⅶ
Ⅳ
12
13
Fig. 7. Catalytic mechanism diagram of the Co-Ru-P@NF catalyst for H2 generation by
14
15
hydrolysis of alkalized NaBH4 solution.
15

Journal of Materials Chemistry A
Page 16 of 19
View Article Online
1
2
As mentioned above, the high catalytic activities of Co-Ru-P@NF series are directly
DOI: 10.1039/C8TA10695A
related to the synergetic effect between Ru and Co along with the unique morphology
associated with the large surface area and the open-channels for effective mass transport. The
negative shift of the Ru 3d binding energy in XPS caused by the partial electron transfer from
Co species to Ru species indicates a higher electron density on Co species as compared to that
of Ru species. Accordingly, the partially electron negative hydrogen atoms preferred to attach
3
4
5
6
3+
−
7
to the Ru atoms. As a result, the BH4 goes a reversible dissociation on Co and Ru metal sites
where the hydrogen atom adsorbs on Ru and BH3 attaches to the Co species. The negatively
charged boron species transfer the electron to Ru through the conductive balk and then the
partially negatively charged hydrogen atom on the Ru surface extracts a hydrogen from water
while the OH ion attacks the BH3 to release the H2 molecule followed by transferring one
hydrogen atom of the BH3 to the free Ru site. The surface adsorbed BH2(OH) species forms
after one cycle. The reaction continues until all the hydrogen atoms are replaced by OH ions
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
50
−
and then the B(OH)4 leaves the surface.
4. Conclusion
In summary, we have successfully developed a simple and novel strategy to fabricate
hierarchically structure of RuP3 loaded CoP@NF nanosheets for H2 generation from NaBH4
hydrolysis in alkaline solution. The XRD, XPS and TEM analysis of the Co-Ru-P@NF
material show that the RuP3 nanoclusters are uniformly dispersed on the surface of vertically
grown CoP nanosheets on the NF, which creates the channels for rapid mass transfer and
sufficient exposure of the active sites. The resulted Co-Ru-P@NF catalyst exhibits an
exceptionally high TOF value of 2123.6 molH2 min-1 mol-1 at 25 °C, which is one of the
Ru
highest result reported so far. The superior catalytic activity is a strong agreement with the low
activation energy (40.3 kJ mol-1). Additionally, the Co-Ru-P@NF catalyst shown a slight decay
16

Page 17 of 19
Journal of Materials Chemistry A
View Article Online
1
2
3
4
5
6
7
8
9
around 8.2% after five cycles demonstrating a good stability towards NaBH4 hydrolysis.
DOI: 10.1039/C8TA10695A
Furthermore, this study might shed light on designing a metal-phosphide based catalyst for
NaBH4 hydrolysis as a high activity, good durability, and reusability.
Acknowledgements
This work has been supported by the National Natural Science Foundation of China (21363003,
21165004, 21163002), Natural Science Foundation of Guangxi Province
(2014GXNSFGA118008, 2014GXNSFFA118003), BAGUI scholar program (2014A001) and
Project of Talents Highland of Guangxi Province.
10
Appendix A. Supplementary data
11
12
13
Figs. S1-S13 and Tables S1-S3 give more details on characterization of our synthesized
materials and their catalytic performance data; additional photograph, XRD, SEM, XPS and
catalytic performance data (PDF).
14
15
16
Conflicts of interest
There are no conflicts to declare.
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Notes and references
1.
2.
3.
X. Zhang, Y. Zhao, X. Jia, Y. Zhao, L. Shang, Q. Wang, G. I. N. Waterhouse, L.-Z.
Wu, C.-H. Tung and T. Zhang, Adv. Energy Mater., 2018, 8, 1702780.
J. Chen, Z.-H. Lu, Q. Yao, G. Feng and Y. Luo, J. Mater. Chem. A, 2018, 6, 20746-
20752.
D. G. Tong, D. M. Tang, W. Chu, G. F. Gu and P. Wu, J. Mater. Chem. A, 2013, 1,
6425-6432.
4.
5.
N. Sahiner and S. Demirci, Appl. Catal. B: Environ., 2017, 202, 199-206.
T. Liu, K. Wang, G. Du, A. M. Asiri and X. Sun, J. Mater. Chem. A, 2016, 4, 13053-
13057.
6.
7.
H.-L. Wang, J.-M. Yan, Z.-L. Wang, S.-I. O and Q. Jiang, J. Mater. Chem. A, 2013, 1,
14957-14962.
Y. Li, T. Gao, Y. Yao, Z. Liu, Y. Kuang, C. Chen, J. Song, S. Xu, E. M. Hitz, B. Liu,
R. J. Jacob, M. R. Zachariah, G. Wang and L. Hu, Adv. Energy Mater., 2018, 8,
1801289.
17

Journal of Materials Chemistry A
Page 18 of 19
View Article Online
DOI: 10.1039/C8TA10695A
1
2
8.
C. Tang, L. Xie, K. Wang, G. Du, A. M. Asiri, Y. Luo and X. Sun, J. Mater. Chem. A,
2016, 4, 12407-12410.
3
4
9.
Q. Yao, Z.-H. Lu, W. Huang, X. Chen and J. Zhu, J. Mater. Chem. A, 2016, 4, 8579-
8583.
5
6
7
10.
F. Fu, C. Wang, Q. Wang, A. M. Martinez-Villacorta, A. Escobar, H. Chong, X.
Wang, S. Moya, L. Salmon, E. Fouquet, J. Ruiz and D. Astruc, J. Am. Chem. Soc.,
2018, 140, 10034–10042.
8
9
11.
12.
H. Zhang, G. Xia, J. Zhang, D. Sun, Z. Guo and X. Yu, Adv. Energy Mater., 2018, 8,
1702975.
Z. Zhang, S. Zhang, Q. Yao, X. Chen and Z.-H. Lu, Inorg. Chem., 2017, 56, 11938-
11945.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
13.
14.
A. Kantürk Figen, K. Taşçi and B. Coşkuner Filiz, Kinet. Catal., 2018, 59, 128-135.
C. Wu, J. Zhang, J. Guo, L. Sun, J. Ming, H. Dong, Y. Zhao, J. Tian and X. Yang,
ACS Sustain. Chem. Eng., 2018, 6, 7451–7457.
C. Wu, J. Guo, J. Zhang, Y. Zhao, J. Tian, T. T. Isimjan and X. Yang, Renew. Energy,
2018, DOI: doi.org/10.1016/j.renene.2018.09.070,
doi.org/10.1016/j.renene.2018.1009.1070.
A. Lale, A. Wasan, R. Kumar, P. Miele, U. B. Demirci and S. Bernard, Int. J. Hydrog.
Energy, 2016, 41, 15477-15488.
J.-X. Kang, T.-W. Chen, D.-F. Zhang and L. Guo, Nano Energy, 2016, 23, 145-152.
M. Irum, M. Zaheer, M. Friedrich and R. Kempe, RSC Adv., 2016, 6, 10438-10441.
Q. Yao, W. Shi, G. Feng, Z.-H. Lu, X. Zhang, D. Tao, D. Kong and X. Chen, J.
Power Sources, 2014, 257, 293-299.
H. X. Nunes, M. J. F. Ferreira, C. M. Rangel and A. M. F. R. Pinto, Int. J. Hydrogen
Energy, 2016, 41, 15426-15432.
L. Wang, L. Huang, C. Jiao, Z. Huang, F. Liang, S. Liu, Y. Wang and H. Zhang,
Catalysts, 2017, 7, 25.
L. Wei and Z. Yuan, AIP Conf. Proc., 2017, 1794, 020004.
C. Li, D. Wang, Y. Wang, G. Li, G. Hu, S. Wu, Z. Cao and K. Zhang, J. Colloid
Interface Sci., 2018, 524, 25-31.
F. Wang, Y. Zhang, Y. Wang, Y. Luo, Y. Chen and H. Zhu, Int. J. Hydrogen Energy,
2018, 43, 8805-8814.
Y. Zou, Y. Yin, Y. Gao, C. Xiang, H. Chu, S. Qiu, E. Yan, F. Xu and L. Sun, Int. J.
Hydrogen Energy, 2018, 43, 4912-4921.
Q. Li, W. Yang, F. Li, A. Cui and J. Hong, Int. J. Hydrog. Energy, 2018, 43, 271-282.
K. A. Holbrook and P. J. Twist, J. Chem. Soc. A, 1971, 0, 890-894.
C.-C. Hou, Q. Li, C. Wang, C.-Y. Peng, Q.-Q. Chen, H.-F. Ye, W. Fu, C.-M. Che and
N. Lopez, Energy Environ. Sci., 2017, 10, 1770-1776.
C. Tang, R. Zhang, W. Lu, L. He, X. Jiang, A. M. Asiri and X. Sun, Adv. Mater.,
2017, 29, 1602441.
Y. Wei, Y. Wang, L. Wei, X. Zhao, X. Zhou and H. Liu, Int. J. Hydrog. Energy,
2018, 43, 592-600.
L. He, D. Zhou, Y. Lin, R. Ge, X. Hou, X. Sun and C. Zheng, ACS Catal., 2018, 8,
3859-3864.
A. H. Tamboli, S. W. Gosavi, C. Terashima, A. Fujishima, A. A. Pawar and H. Kim,
Chemosphere, 2018, 202, 669-676.
X. Peng, D. Chen, X. Yang, D. Wang, M. Li, C.-C. Tseng, R. Panneerselvam, X.
Wang, W. Hu, J. Tian and Y. Zhao, ACS Appl. Mater. Interfaces, 2016, 8, 33673-
33680.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
L. Cui, Y. Xu, L. Niu, W. Yang and J. Liu, Nano Res., 2017, 10, 595-604.
18

Page 19 of 19
Journal of Materials Chemistry A
View Article Online
1
2
35.
L. Wei, M. Ma, Y. Lu, S. Zhang, J. Gao and X. Dong, Funct. Mater. Lett.,D2O0I:1170.,101390/,C8TA10695A
1750065.
3
4
5
36.
37.
K. Mori, K. Miyawaki and H. Yamashita, ACS Catal., 2016, 6, 3128-3135.
Q. Yao, Z.-H. Lu, Y. Yang, Y. Chen, X. Chen and H.-L. Jiang, Nano Res., 2018, 11,
4412-4422.
6
7
8
9
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
X. Yang, H. Li, A.-Y. Lu, S. Min, Z. Idriss, M. N. Hedhili, K.-W. Huang, H. Idriss
and L.-J. Li, Nano Energy, 2016, 25, 42-50.
X. Yang, A.-Y. Lu, Y. Zhu, M. N. Hedhili, S. Min, K.-W. Huang, Y. Han and L.-J.
Li, Nano Energy, 2015, 15, 634-641.
T. Tang, Q. Gan, X. Guo, H. Dong, J. Zhang, Y. Zhao, J. Tian and X. Yang, Sustain.
Energ. Fuels, 2018, 2, 229-236.
Y. Zeng, S. Tian, D. Wang, H. Dong, X. Cheng, Y. Zhao, J. Tian and X. Yang,
ChemistrySelect, 2017, 2, 9291-9297.
C. Jing-Qi, G. Wen-Kun, L. Jia-Hui, D. Bin, Y. Kai-Li, Q. Jun-Feng, L. Bin, C.
Yong-Ming and L. Chen-Guang, ChemSusChem, 2018, 11, 743-752.
S. Liu, Q. Liu, Y. Lv, B. Chen, Q. Zhou, L. Wang, Q. Zheng, C. Che and C. Chen,
Chem. Commun., 2017, 53, 13153-13156
W. Gao, M. Yan, H.-Y. Cheung, Z. Xia, X. Zhou, Y. Qin, C.-Y. Wong, Y. Qu, C.-R.
Chang and J. C. Ho, Nano Energy, 2017, 38, 290-296.
Z. Pu, I. S. Amiinu, Z. Kou, W. Li and S. Mu, Angew. Chem.-Int. Edit., 2017, 56,
11559-11564.
H. Zhang, X. Li, A. Hähnel, V. Naumann, C. Lin, S. Azimi, S. L. Schweizer, A. W.
Maijenburg and R. B. Wehrspohn, Adv. Funct. Mater., 2018, 28, 1706847.
S. Cao, Y. Chen, H. Wang, J. Chen, X. Shi, H. Li, P. Cheng, X. Liu, M. Liu and L.
Piao, Joule, 2018, 2, 549-557.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
48.
49.
D. Kılınç, Ö. Şahı̇n and C. Saka, Int. J. Hydrog. Energy, 2018, 43, 251-261.
L. Zhou, J. Meng, P. Li, Z. Tao, L. Mai and J. Chen, Mater. Horizons, 2017, 4, 268-
273.
50.
U. B. Demirci and P. Miele, C. R. Chim., 2014, 17, 707-716.
30
19