Studies on catalytic behavior of Co-Ni-B in hydrogen production by hydrolysis of NaBH4

Article abstract of DOI:10.1016/j.molcata.2008.09.014

Catalyst powders of Co-B, Ni-B, and Co-Ni-B, with different molar ratios of Co/Ni, were synthesized by chemical reduction of cobalt and nickel salts with sodium borohydride at room temperature. Surface morphology and structural properties of the catalyst

Full text of DOI:10.1016/j.molcata.2008.09.014

Journal of Molecular Catalysis A: Chemical 298 (2009) 1–6
Contents lists available at ScienceDirect
Journal of Molecular Catalysis A: Chemical
journal homepage: www.elsevier.com/locate/molcata
Studies on catalytic behavior of Co–Ni–B in hydrogen
production by hydrolysis of NaBH4
a,∗
a
a
b
R. Fernandes , N. Patel , A. Miotello , M. Filippi
a
Dipartimento di Fisica, Università degli Studi di Trento, I-38100 Povo (Trento), Italy
Fondazione Bruno Kessler – Ricerca Scientifica e Tecnologica, I-38100 Povo (Trento), Italy
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 August 2008
Received in revised form 4 September 2008
Accepted 4 September 2008
Available online 20 September 2008
Catalyst powders of Co–B, Ni–B, and Co–Ni–B, with different molar ratios of Co/Ni, were synthesized
by chemical reduction of cobalt and nickel salts with sodium borohydride at room temperature. Sur-
face morphology and structural properties of the catalyst powders were studied using scanning electron
microscopy (SEM) and X-ray diffraction (XRD) respectively. Surface electronic states and composition of
the catalysts were studied by X-ray photoelectron spectroscopy (XPS). The catalytic activity of the pow-
ders has been tested by measuring the H2 generation rate and yield by the hydrolysis of NaBH4 in basic
medium. Co–Ni–B with the Co/(Co + Ni) molar ratio (ꢀCo) of 0.85 exhibited much superior activity with
highest H2 generation rate as compared to the other powder catalysts. The enhanced activity obtained
with Co–Ni–B (ꢀCo = 0.85) powder catalyst could be attributed to: large active surface area and electron
transfer by alloying large quantity of B to active Co and Ni sites on the surface of the catalyst. The electron
enrichment, detected in the XPS spectra on active Co and Ni sites in Co–Ni–B, higher than that of Co–B
and Ni–B seems to be able to facilitate the catalysis reaction by providing the negative charge electron
required by the reaction. Synergetic effect of the Co and Ni atoms in Co–Ni–B catalyst is able to lower the
Keywords:
H2 generation
Hydrolysis
Sodium borohydride
Co–Ni–B catalyst
−1
−1
activation energy up to 34 kJ mol as compared to 45 kJ mol obtained with Co–B powder. Structural
modification, caused by the heat-treatment at 773 K for 2 h in Ar atmosphere, was not able to change the
activity of the Co–Ni–B powder.
©
2008 Elsevier B.V. All rights reserved.
1
. Introduction
the reactant [5]. Hydrogen is generated from NaBH4 by following
hydrolysis reaction, with the important advantage of producing half
of the hydrogen from the water solvent [6]:
Proton exchange membrane fuel cell (PEMFC) is a clean and
efficient alternative power source for transportation and personal
electronics applications, where low system weight and portability
are important. Pure hydrogen is used as the fuel in PEMFC [1] but
on industrial level, H2 is mostly produced by steam reforming of
natural gas and so the final product contains carbon contamination
NaBH + 2H O → NaBO + 4H ↑
(1)
4
2
2
2
The efficiency of hydrogen production can be significantly
enhanced by use of catalyst during the reaction. Many organic and
inorganic acids are able to effectively enhance the hydrolysis reac-
tion rate; however the reaction usually becomes uncontrollable [7].
On other hand, solid state catalysts such as precious (generally func-
tionalized with support) or transition metals and their salts are
found to be very efficient in accelerating the hydrolysis reaction in
a controllable manner.
(
CO and CO). The presence of carbon monoxide (even at ppm level)
2
in the hydrogen gas reduces the performance of PEMFC because of
catalyst poisoning [2].
Chemical hydrides are very attractive materials for pure hydro-
gen supply to the fuel cells at room temperature [3]. Among them,
aqueous sodium borohydride (NaBH ) seems to be an ideal hydro-
4
Catalysts like Ru supported on anion-exchange resin [8], fluo-
rinated Mg based alloy [9], Pt [10] and Pd supported on carbon
gen source because it is stable, non-flammable and non-toxic in
nature with hydrogen storing capability of 10.8 wt.% [4]. The reac-
tion product (borax), obtained after removal of hydrogen from
[
11], PtRu supported on metal oxide [12], raney Ni and Co, and even
nickel and cobalt borides [13–15] are generally used to accelerate
NaBH , is environmentally clean and can be recycled to generate
4
the hydrolysis reaction of the NaBH . Co and Ni borides are mostly
4
considered as good candidates for catalyzed hydrolysis reaction of
NaBH4 owing to their good catalytic activity and low cost. These
catalyst materials can be effortlessly synthesized by the simple pro-
cedure of chemical reduction method by which transition metal
∗ Corresponding author.
E-mail address: fernandes@science.unitn.it (R. Fernandes).
1381-1169/$ – see front matter © 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2008.09.014

2
R. Fernandes et al. / Journal of Molecular Catalysis A: Chemical 298 (2009) 1–6
ions are brought to the metallic state by reducing agent [14]. In our
previous work, Co–B catalysts developed in form of films showed a
performance similar to the noble metals [15,16]. It was also found
that these non-noble metals (Co and Ni) demonstrate the better
activity only when used in boride form because boron is able to
protect the active metal sites (Co or Ni) from oxidation by elec-
tron transfer [17]. Thus, it is important to understand the role of
boron to achieve the best configuration/composition for the cata-
lyst. The recent work of Li et al. [18] demonstrates that the mixed
boride in form of Co–Ni–B is able to better work for the hydro-
genation of nitriles just because of the boron enrichment on the
surface. Recently, Co–Ni–B catalyst was also used for the hydrolysis
of NaBH [19] but the authors did not studied the role of the atomic
4
elements concentration in the catalyst because they only used a
single Co/(Co + Ni) molar ratio (ꢀCo) equal to 0.50.
In our present work, we examined several Co/Ni atomic ratios
in Co–Ni–B catalyst in order to establish the optimum condition
to have the best efficiency in the catalytic reaction. We discovered
indeed that, Co/Ni ratio is an important parameter to determine
the efficiency of the catalyst, a result non-previously reported. In
addition, we have also compared Co–Ni–B catalyst with Co–B and
Ni–B in order to understand the role of each atomic element in the
catalytic activity, by also specifically looking at the XPS results on
binding electron energies. The favourable activation energy value
obtained with Co–Ni–B, as compared to Co–B, suggests that elec-
tronic synergetic effects operate with Co and Ni atoms in Co–Ni–B
which help to enhance the catalytic activity. Possibly, transient elec-
tronic states are favoured with Co and Ni atoms in the Co–Ni–B
powder at appropriate atomic composition. This new research
activity is important to contribute to possible application to on-
board reactor.
Fig. 1. Hydrogen generation yield as a function of reaction time obtained by hydrol-
ysis of alkaline NaBH4 (0.025 M) with Co–B, Ni–B, and Co–Ni–B (ꢀCo = 0.85) catalyst
powder.
ment equipped with a monochromatic Al K␣ (1486.6 eV) X-ray
source and a hemispherical analyzer. No electrical charge compen-
sation was required to perform the analysis.
2.3. Activity measurement
For catalytic activity measurements, an alkaline-stabilized solu-
tion of sodium borohydride (pH 13, 0.025 ± 0.001 M) (Rohm and
Haas), was prepared by addition of NaOH (0.025 M). The titre of
reagent was independently measured through iodometric method
2. Experimental
[
20]. The hydrogen generation rate was measured through a gas
volumetric method in an appropriate reaction chamber with ther-
mostatic bath, wherein the temperature was kept constant within
accuracy ± 0.1 K. The chamber was equipped with pressure sensor,
stirrer system, catalyst insertion device and also coupled with an
electronic precision balance to accurately measure the weight of
water volumes displaced by the hydrogen volumes produced dur-
ing the reaction course. A detailed description of the measurement
apparatus is given in Ref. [21]. In all the runs, the catalyst was placed
on the appropriate device inside the reaction chamber and the sys-
tem was sealed. In order to make comparison we plot the time
dependences versus stoichiometric hydrogen production yield (%)
instead of hydrogen volume (ml). Catalyst powder was added to
200 ml of the above solution under continuous stirring.
2
.1. Catalyst preparation
Co–Ni–B catalysts were prepared by adding NaBH4 as reduc-
ing agent into the aqueous mixture solution of cobalt chloride
CoCl ) and nickel chloride (NiCl ) under vigorous stirring at room
(
2
2
temperature. Excess amount of borohydride was used in order to
completely reduce Co and Ni cations to metals. The resulting black
powder, separated from solution during reaction course, was fil-
tered, extensively washed with distilled water and ethanol (99.9%)
in order to remove Cl and Na+ ions, and then dried in continuous
−
nitrogen flow at around 323 K.
The Co/(Co + Ni) molar ratio (ꢀCo) in the Co–Ni–B samples was
adjusted by varying the concentration of Co and Ni salts in the start-
ing solution. Ni–B (ꢀCo = 0) and Co–B (ꢀCo = 1) were also prepared in
a similar manner when only NiCl or CoCl was used in the solution
respectively. One set of Co–Ni–B and Co–B powder was annealed
at 773 K for 2 h in Ar atmosphere to study the effect of the lattice
structural variation on the catalytic activity.
2
2
3. Results and discussion
Fig. 1 presents the hydrogen generation yield as function of
time obtained by the hydrolysis of alkaline NaBH4 (0.025 M) solu-
tion using Co–B, Ni–B, and Co–Ni–B (ꢀCo = 0.85) catalyst powder
at 298 K. The expected total amount of H2 has been measured, no
matter of the type of catalyst used. The generation rate initially
increases to a maximum value and then decreases with time as
the NaBH4 concentration decreases in the solution: this suggests
the non-zero order of the reaction kinetics. Co–Ni–B (ꢀCo = 0.85)
catalyst shows much better catalytic activity as compared to the
same amount (≈15 mg) of Co–B and Ni–B powder. Fitting method
as mentioned in our pervious work [15] has been utilized to obtain
maximum hydrogen generation rates (Rmax) which are summarized
in Table 1. Co–Ni–B (ꢀCo = 0.85) shows the highest Rmax which is
nearly 1.7 and 11.5 times higher than the Co–B and Ni–B powder,
respectively.
2.2. Catalyst characterization
The surface morphologies of all catalyst powders were stud-
ied by scanning electron microscope (SEM-FEG, JSM 7001F, JEOL)
equipped with energy-dispersive spectroscopy analysis (EDS, INCA
PentaFET-x3) to verify the composition of the samples. Struc-
tural characterization of the catalyst powders was determined by
conventional X-ray diffraction (XRD) using the Cu K␣ radiation
(
ꢁ = 1.5414 Å) in Bragg–Brentano (ꢂ–2ꢂ) configuration.
The studies on surface electronic states and composition of the
catalysts were carried out by X-ray photoelectron spectroscopy
XPS). XPS spectra were acquired within a SCIENTA ESCA200 instru-
(

R. Fernandes et al. / Journal of Molecular Catalysis A: Chemical 298 (2009) 1–6
3
Table 1
Maximum hydrogen generation rate obtained with Co–B, Co–Ni–B (ꢀCo = 0.50, 0.65,
.75, 0.85, and 0.90) and Ni–B powders by hydrolysis of alkaline NaBH4 (0.025 M)
0
solution.
Catalyst
powder
Co/(Co + Ni)
molar ratio (ꢀCo)
Maximum hydrogen generation
rate (ml/(min g) catalyst)
Ni–B
0
∼100
∼491
∼644
∼832
∼1175
∼779
∼681
Co–Ni–B
Co–Ni–B
Co–Ni–B
Co–Ni–B
Co–Ni–B
Co–B
0.50
0.65
0.75
0.85
0.90
1
In Fig. 2 we present SEM images of Co–B, Co–Ni–B (ꢀCo = 0.85),
and Ni–B powders. Both Co–B and Ni–B are present in form of
well-dispersed spherical particles with the average size of about
30 and 18 nm, respectively. In the case of Co–Ni–B catalyst the
particles sizes seem to be smaller as compared to the other pow-
ders and they are difficult to measure because they are embedded
in cotton-like filamentary matrix of nanometer size. This kind of
morphology might be helpful to enhance the active surface area
of the Co–Ni–B catalyst. XRD pattern (figure not shown) of Co–B,
Co–Ni–B (ꢀCo = 0.85), and Ni–B powders showed a single broad peak
◦
at around 2ꢂ = 45 thus indicating the amorphous nature of the cat-
alyst powders. The SEM and XRD results obtained in the present
case are consistent with those reported in the literatures [18,22].
To try to understand the enhanced activity of Co–Ni–B
(
ꢀCo = 0.85), it is necessary to study the surface electronic inter-
action between the atoms in the compound. Thus, XPS spectra
of Co–B, Co–Ni–B (ꢀCo = 0.85), and Ni–B catalyst powders were
acquired and reported in Fig. 3. In all the catalyst powders, two
peaks appear in Co2p3/2 and Ni2p3/2 levels with the binding ener-
gies of 778.4 and 781.9 eV for Co, and 852.8 and 856.3 eV for Ni
indicating that metals exist in both the elemental and oxidized
states respectively. The peaks due to oxidized Co and Ni are mainly
related to Co(OH)2 and Ni(OH)2 which would have been formed
Fig. 3. XPS spectra of B1s, Co2p3/2 and Ni2p3/2 level for Co–B, Ni–B, and Co–Ni–B
(
ꢀCo = 0.85) catalyst powder.
during the catalyst preparation reaction between NaBH and metal
salts [23,24]. Two XPS peaks with binding energy (BE) of 188.1 and
4
Table 2
Surface atomic composition of catalyst powders obtained by the XPS spectra.
192.5 eV are also observed for the B1s level, which are assigned to
elemental and oxidized boron, respectively [23]. If one compares
the BE of pure boron (187.1 eV) [25] with that of the elemental boron
in all the catalyst powders there is positive shift of 1 eV. This shift
indicates an electron transfer from alloying B to vacant d-orbital of
metallic Ni and/or Co which makes boron electron deficient while
Ni and/or Co metals are enriched with the electron in all the catalyst
powders. Electron-enriched metal active sites repel the adsorption
of oxygen atoms while they are strongly adsorbed by the electron-
deficient B. In other words, alloying B effectively protects metals
from oxidation [26,27]. The BE of metallic Co in Co–Ni–B is 0.2 eV
lower than that in the Co–B, whereas BE of metallic Ni in Co–Ni–B is
Catalyst powders
Co (at.%)
Ni (at.%)
B (at.%)
Co–B
Co–Ni–B (ꢀCo = 0.85)
Ni–B
64
50
–
–
9
64
36
41
39
Co and Ni metals may exchange electrons more easily than the Co–B
and Ni–B catalyst: this could be connected to the B-enrichment
in Co–Ni–B catalyst as seen by the compositional analysis of XPS
spectra (Table 2) and also reported by Li et al. [18] who also per-
formed theoretical calculations using DFT method to show that
the increase of the B content on surface would contribute more
0.1 eV lower than that in Ni–B. This proves that in Co–Ni–B catalyst,
Fig. 2. SEM micrographs of (A) Ni–B, (B) Co–Ni–B (ꢀCo = 0.85) and (C) Co–B catalyst powder.

4
R. Fernandes et al. / Journal of Molecular Catalysis A: Chemical 298 (2009) 1–6
Fig. 5. Hydrogen generation yield as a function of reaction time with Co–Ni–B
ꢀCo = 0.85) catalyst measured at four different temperatures by hydrolysis of alka-
(
line NaBH4 (0.025 M) solution. Inset shows the Arrhenius plot of the H2 generation
rates with Co–Ni–B (ꢀCo = 0.85) powder.
Fig. 4. Hydrogen generation yield as a function of reaction time obtained by hydrol-
ysis of alkaline NaBH4 (0.025 M) with Ni–B, Co–Ni–B (ꢀCo = 0.50, 0.65, 0.75, 0.85, and
0
.90) and Co–B catalyst powder.
as compared to Ni–B thus indicating that Co metal is more active
site than Ni for catalytic hydrolysis reaction. The increment in the
activity by increasing the amount in Co is due to the fact that less
active Ni sites are replaced by more active Co sites. However, the
effect of B enrichment on the surface of the Co–Ni–B (ꢀCo = 0.90,
0.85 and 0.75) causes the superior activity than Co–B as discussed
previously.
electrons to metallic Ni or Co in their corresponding amorphous
alloys.
The H2 production from the metal-catalyzed hydrolysis of
NaBH4 is proposed to take place by following three kinetics steps
−
[
11]. In the first step, BH4 ions are chemisorbed on the metal (Ni
−
and/or Co) atoms while in the second step the hydride ion H is
transferred from BH4 ion to an unoccupied adjacent (Ni and/or
Co) metal atom. In the last step, this hydrogen atom acquires a neg-
ative charge in form of electron from the metal and leaves the site
in hydridic form (H ) which reacts with the water molecule to pro-
duce H2 and OH ion. OH reacts with boron in BH3 to produce
the BH (OH) ion. The cycle of hydrogen absorption on the metal
sites continues till BH (OH) forms B(OH)4 . Molecular hydrogen
is released during the full cycle. Looking at the mechanism men-
tioned above, electron enriched metal active sites will be able to
facilitate the catalysis reaction by providing the negative charge
electron required by the hydrogen atom in the last step. These elec-
trons are provided by the alloying boron to the active metal sites,
as discussed when reporting the XPS results. Thus, the higher con-
centration of boron in Co–Ni–B catalyst, as compared to Co–B and
Ni–B, plays a significant role in enhancing the catalytic activity.
Co and Ni molar ratio was varied from ꢀCo = 0.5 to 0.9 in the
Co–Ni–B powder catalyst in order to study the effect of active metal
concentration on catalytic activity. The Co and Ni molar ratio was
evaluated by EDS and XPS. Fig. 4 presents the hydrogen generation
yield as function of time measured by hydrolysis of alkaline
NaBH4 (0.025 M) solution using Co–Ni–B catalyst powder with
different molar ratio of Ni and Co. The corresponding maximum
H2 generation rate (Rmax) is report in Table 1. Rmax obtained by
pure Ni–B catalyst is always lower than that measured by other
powders containing Co. By increasing the Co content relative to Ni
in the Co–Ni–B powder, the rate increases and reaches the highest
In another set of experiments, the hydrogen generation from
catalytic hydrolysis of alkaline NaBH4 (0.025 M) solution was mea-
sured at different solution temperature ranging from 298 to 313 K
by using Co–Ni–B (ꢀCo = 0.85) (Fig. 5) and Co–B (Fig. 6) cata-
lyst powders. As expected, H2 generation rate increases with the
temperature. The Arrhenius plot (inset of Fig. 5 and Fig. 6) of
the hydrogen production rate gives activation energies of about
−
−
−
−
−
3
−
−
−1
3
34 ± 1 and 45 ± 2 kJ mol , within experimental errors, for Co–Ni–B
(ꢀ
Co
= 0.85) and Co–B powder catalyst, respectively. This value for
Co–Ni–B powder is lower than that found by Amendola et al.
−1
[
8] using Ru catalyst (47 kJ mol ), while Kaufman and Sen [28]
−1
−1
−1
obtained 75 kJ mol
for Co, 71 kJ mol
for Ni, and 63 kJ mol
for Raney nickel. The activation energy for the Co–B catalyst mea-
Rmax of about ∼1175 ml/min/g for molar ratio of ꢀ = 0.85 which
Co
is even superior than pure Co–B powder. With further increase of
the molar ratio ꢀCo to 0.9, the activity of the powder decreases.
The catalytic activity of the powders decrease in following order:
Co–Ni–B(ꢀCo = 0.85) > Co–Ni–B(ꢀCo = 0.75) > Co–Ni–B(ꢀCo = 0.90) >
Co–B(ꢀCo = 1) > Co-Ni–B(ꢀCo = 0.65) > Co–Ni–B(ꢀCo = 0.50) > Ni–B
Fig. 6. Hydrogen generation yield as a function of reaction time with Co–B catalyst
measured at four different temperatures by hydrolysis of alkaline NaBH4 (0.025 M)
solution. Inset shows the Arrhenius plot of the H2 generation rates with Co–B pow-
der.
(
ꢀCo = 0). The measurements were repeated at least three times to
verify the results obtained in the present case. As observed in the
previous results, the Co–B shows much higher catalytic activity

R. Fernandes et al. / Journal of Molecular Catalysis A: Chemical 298 (2009) 1–6
5
Fig. 8. XRD pattern of Co–Ni–B (ꢀCo = 0.85) catalyst powder untreated and treated
in Ar gas atmosphere at 773 K for 2 h.
Fig. 7. Hydrogen generation yield as a function of reaction time with Co–Ni–B
ꢀCo = 0.85) catalyst of four different concentrations by hydrolysis of alkaline
(
NaBH4 (0.025 M) solution. Insert shows the plot of ln(H2 generation rate) vs.
ln(concentration of catalyst).
The value of the slope is 0.95 thus indicating that the hydrolysis of
NaBH4 is first order reaction with respect to the concentration of
Co–Ni–B (ꢀCo = 0.85) powder catalyst.
sured in the present case is same as that obtained by Lee et al. [6]
−
1
with structured Co–B catalyst powder (45 kJ mol ). The activation
To study the effect of structural modification on catalytic
activity, Co–Ni–B (ꢀCo = 0.85) and Co–B were heat-treated in Ar
atmosphere at 773 K for 2 h. XRD pattern (Fig. 8) of the annealed
Co–Ni–B (ꢀCo = 0.85) powder show that annealing causes structural
modification in the powder leading to the formation of crystalline
Co metal phase with the crystal size of around 15 nm. Morpho-
logical studies performed by SEM also show analogous results for
annealed Co–Ni–B powder catalyst. The SEM images (Fig. 9) clearly
demonstrate the transformation from the well-dispersed spherical
particle morphology of the fresh powders (Fig. 9A) to porous crys-
tallite morphology after annealing at 773 K (Fig. 9B). The hydrogen
generation yield, as function of time, obtained by hydrolysis of alka-
−1
energy of about 62 kJ mol is reported by Ingersoll et al. [19] by
using Co–Ni–B powder catalyst with similar atomic concentration
of Co and Ni. Our results are for ꢀCo = 0.85. The favourable activa-
tion energy value obtained with Co–Ni–B, as compared to Co–B,
suggests that electronic synergetic effects operate with Co and Ni
atoms in Co–Ni–B which help to enhance the catalytic activity. Pos-
sibly, transient electronic states are favoured with Co and Ni atoms
in the Co–Ni–B powder at appropriate atomic composition.
To identify the reaction order in connection to the catalyst con-
centration, the H2 generation yield was measured by hydrolysis of
alkaline NaBH4 (0.025 M) solution using four different amounts of
Co–Ni–B (ꢀCo = 0.85) catalyst, i.e., 10, 15, 20, 25 mg (Fig. 7) at 298 K.
The figure clearly indicates that the hydrolysis of NaBH4 depends
on the catalyst concentration because when the amount of catalyst
increases, then the reaction takes much less time to reach the max-
imum expected H2 generation yield. The hydrogen generation rate
line NaBH (0.025 M) solution using annealed Co–Ni–B (ꢀ = 0.85)
4
Co
at 293 K, is reported in Fig. 10. However, the structural changes did
not bring any differences in the catalytic activity for the annealed
Co–Ni–B (ꢀCo = 0.85) powder when compared with untreated pow-
der. Co–B powder annealed at 773 K in similar condition, shows
analogous structural modification similar to that of Co–Ni–B. How-
ever, there is now a decrease in the hydrogen generation rate as
compared to the untreated powder (Fig. 11). Lee et al. [6] and Wu et
(
R) seems to be proportional to the catalyst concentration when the
concentrations of all the other reactants are kept constant:
x
R ˛ [concentration of catalyst]
(2)
al. [29] also reported a decrement in the H generation rate for Co–B
2
By plotting ln(R) vs. ln(concentration of catalyst) one obtains the
straight line of the inset of Fig. 7 and the slope provides the value of
the reaction order (x) with respect to the concentration of catalyst.
powder when annealed above 573 K and the authors discussed the
results in terms of the crystallization of Co metal. However, our
present results indicate that even after crystallization of the Co
Fig. 9. SEM micrographs of Co–Ni–B (ꢀCo = 0.85) catalyst powder (A) untreated and (B) treated in Ar gas atmosphere at 773 K for 2 h.

6
R. Fernandes et al. / Journal of Molecular Catalysis A: Chemical 298 (2009) 1–6
ysis of NaBH . It was proved that the presence of mixed Co–Ni
4
with B atoms results in an enhanced catalytic effect with respect
to Co–B or Ni–B powders. The effect is preserved after anneal-
ing of the Co–Ni–B powder and Co phase formation, as opposed
to phase formation in Co–B powder. Possibly, transient electronic
states are favoured with Co and Ni atoms in the Co–Ni–B powder
that should be further investigated. In addition, surface morpholo-
gies as observed in Figs. 2B and 9, which are different from that
pertinent to Co–B and Ni–B, could constitute an additional key to
explain the reported results.
Acknowledgements
We thank Nicola Bazzanella for SEM-EDS analysis and Cristina
Armellini for XRD analysis. The research activity is financially sup-
ported by the Hydrogen-FISR Italian project.
References
Fig. 10. Hydrogen generation yield as a function of reaction time with Co–Ni–B
(ꢀCo = 0.85) catalyst powder untreated and heat-treated at 773 K obtained by hydrol-
ysis of alkaline NaBH4 (0.025 M) solution.
[1] J.M. Ogden, T.G. Kreutz, M.M. Steinbugler, Fuel Cell. Bull. 3 (16) (2000) 5–13.
[
[
2] A.L. Dicks, J. Power Sources 61 (1996) 113–124.
3] R.B. Biniwale, S. Rayalu, S. Devotta, M. Ichikawa, Int. J. Hydrogen Energy 33
(
2008) 360–365.
[
4] S.C. Amendola, S.L. Sharp-Goldman, M.S. Janjua, M.T. Kelly, P.J. Petillo, M. Binder,
J. Power Sources 85 (2000) 186–189.
[
[
5] U.B. Demirici, F. Garin, J. Mol. Catal. A: Chem. 279 (2007) 57–62.
6] J. Lee, K.Y. Kong, C.R. Jung, E. Cho, S.P. Yoon, J. Han, T. Lee, S.W. Nam, Catal. Today
120 (2007) 305–310.
[
[
[
7] H.I. Schlesinger, H.C. Brown, A.E. Finholt, J.R. Gilbreath, H.R. Hockstra, E.K. Hyde,
J. Am. Chem. Soc. 75 (1953) 215–219.
8] S.C. Amendola, S.L. Sharp-Goldman, M.S. Janjua, N.C. Spencer, M.T. Kelly, P.J.
Petillo, M. Binder, Int. J. Hydrogen Energy 25 (2000) 969–975.
9] S. Suda, Y.M. Sun, B.H. Liu, Y. Zhou, S. Morimitsu, K. Arai, N. Tsukamoto, M.
Uchida, Y. Candra, Z.P. Li, Appl. Phys. A: Mater. Sci. Process 72 (2001) 209–212.
[
[
10] Y. Bai, C. Wu, F. Wu, B. Yi, Mater. Lett. 60 (2006) 2236–2239.
11] G. Guella, C. Zanchetta, B. Patton, A. Miotello, J. Phys. Chem. B 110 (2006)
7024–17033.
1
[
[
12] P. Krishnan, T.H. Yang, W.Y. Lee, C.S. Kim, J. Power Sources 143 (2005) 17–23.
13] B.H. Liu, Z.P. Li, S. Suda, J. Alloys Compd. 415 (2006) 288–293.
[
[
[
14] S.U. Jeong, E.A. Cho, S.W. Nam, I.H. Oh, U.H. Jung, S.H. Kim, Int. J. Hydrogen
Energy 32 (2007) 1749–1754.
15] N. Patel, G. Guella, A. Kale, A. Miotello, B. Patton, C. Zanchetta, L. Mirenghi, P.
Rotolo, Appl. Catal. A: Gen. 323 (2007) 18–24.
16] N. Patel, R. Fernandes, G. Guella, A. Kale, A. Miotello, B. Patton, C. Zanchetta, J.
Phys. Chem. C 112 (2008) 6968–6976.
[
17] H. Li, Y. Wu, Ying Wan, J. Zhang, W. Dai, M. Qiao, Catal. Today 93 (2004)
93–503.
18] H. Li, Y. Wu, J. Zhang, W. Dai, M. Qiao, Appl. Catal. A: Gen. 275 (2004) 199–206.
19] J.C. Ingersoll, N. Mani, J.C. Thenmozhiyal, A. Muthaiah J. Power Sources 173
2007) 450–457.
20] D.A. Lyttle, E.H. Jensen, W.A. Struck, Anal. Chem. 24 (1952) 1843–1844.
4
Fig. 11. Hydrogen generation yield as a function of reaction time with Co–B cata-
lyst powder untreated and heat-treated at 773 K obtained by hydrolysis of alkaline
NaBH4 (0.025 M) solution.
[
[
(
[
[
21] C. Zanchetta, B. Patton, G. Guella, A. Miotello, Meas. Sci. Technol. 18 (2007)
metal phase in Co–Ni–B powder, the same powder maintains its
catalytic efficiency. Thus it shows that the Co–Ni–B catalyst is stable
and useful for high temperature application.
N21–N26.
[22] J. Shen, Y. Chen, J. Mol. Catal. A: Chem. 273 (2007) 265–276.
[23] W.L. Dai, M.H. Qiao, J.F. Deng, Appl. Surf. Sci. 120 (1997) 119–124.
[24] A. Lebugle, U. Axelsson, R. Nyholm, N. Martensson, Phys. Scr. 23 (1981) 825–827.
[25] H. Li, H. Li, W.L. Dai, Z. Fang, J.F. Deng, Appl. Surf. Sci. 152 (1999) 25–34.
4
. Conclusions
[26] H. Li, Y. Wu, H. Luo, M. Wang, Y. Xu, J. Catal. 214 (2003) 15–25.
27] S. Yoshida, H. Yamashita, T. Funabiki, T. Yonezawa, J. Chem. Soc. Faraday Trans.
, 80 (1984) 1435–1446.
28] C.M. Kaufman, B. Sen, J. Chem. Soc., Dalton Trans. 2 (1985) 307–313.
[29] C. Wu, F. Wu, Y. Bai, B. Yi, H. Zhang, Mater. Lett. 59 (2005) 1748–1751.
[
1
We have investigated the role of atomic composition in Co–Ni–B
[
powder in the catalytic activity for hydrogen production by hydrol-