Materials Transactions, Vol. 55, No. 6 (2014) pp. 892 to 898
© 2014 The Japan Institute of Metals and Materials
Preparation and Hydrolysis of Aluminum Based Composites
for Hydrogen Production in Pure Water
Huihu Wang1,2, J. Lu1, S. J. Dong1,2,+, Y. Chang2,3, Y. G. Fu1 and Ping Luo1,2
1
School of Mechanical Engineering, Hubei University of Technology, Wuhan 430068, China
Hubei Provincial Key Laboratory of Green Materials for Light Industry, Hubei University of Technology, Wuhan 430068, China
3
School of Materials Science and Engineering, Hubei University of Technology, Wuhan 430068, China
2
A series of Al based composites were prepared using mechanical milling method in this paper. Effects of additives including CaO, NaCl
salt and low melting point metals (Ga, In, and Sn) on the hydrolysis activity of Al based composites were evaluated in pure water. Scanning
electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used for the microstructure analysis of as-prepared samples and their
hydrolysis products. The results showed that the addition of CaO, NaCl salt and low melting point metals can effectively improve the hydrolysis
properties of Al based composites. Especially, Al alloys-CaO­NaCl composites exhibited a higher hydrogen yields than Al­CaO and Al­CaO­
NaCl materials. The SEM images displayed that NaCl salt particles were homogeneously distributed on the surface of Al based composites and
inserted into Al matrix, which may damage the surface oxide layer of Al. Furthermore, the size of NaCl salt particles was much smaller in Al
alloys-CaO­NaCl composites than that in Al­CaO­NaCl composites. The XRD patterns identified that the hydrolysis products were mainly
composed of AlO(OH) and Al(OH)3. The microstructure-related hydrolysis reaction mechanism of Al based composites was proposed finally.
[doi:10.2320/matertrans.M2013425]
(Received November 26, 2013; Accepted April 3, 2014; Published May 16, 2014)
Keywords: aluminum based composites, mechanical milling, hydrogen
1.
Introduction
Hydrogen energy has been considered as an alternative of
carbon-based fossil fuel for its clean combustion. It can be
used to generate electricity through fuel cells or produce heat
by directly burning without producing any carbon emissions.
Therefore, the wide use of hydrogen is a potential route to
reduce the negative impact of the enormous carbon emissions
caused by fossil fuels burning.1) Currently, gas,2) coal3) and
petroleum4) are the main resources for the industrial hydrogen
production. As these resources still belongs to the fossil fuel,
the hydrogen production methods based on it could not offer
the fundamental solution to the environmental crisis arising
by fossil fuel burning. Other energy sources including
electricity, solar energy, and biomass energy which involves
in the water electrolysis,5,6) water splitting7) and biomass
process8) also have been tried to produce hydrogen. Although
it seems that these resources are more important than the
fossil resources, they are also facing many problems, such as
high power consumption and low conversion efficiency.
Recently, hydrogen produced by the hydrolysis of active
metals, such as Mg, Al, etc. in water has attracted more and
more attention for the high hydrogen storage value of metals
and the simplicity of reaction system. More important is that
the hydrolysis reaction is not involved in carbon emissions,9)
thus it is also a green process. Among the active metals, Al is
proved to be the best for practical application because of its
abundance and low cost. Furthermore, the aluminum oxide
hydroxide as the byproducts of hydrolysis reaction is widely
used in alumina production, fire inhibition, water treatment,
paper making etc. The major obstacle of Al applying for
hydrogen production is the thin and dense oxide layer formed
on the surface of Al, which may prohibit the hydrolysis of Al.
Although alkaline and acid solution can be used to get rid of
+
Corresponding author, E-mail: [email protected]
this oxide layer,10,11) its corrosion characteristic makes the
reaction system not suitable for practical applications.
Therefore, it is of great importance to develop the method
for removing the oxide layer and increasing the activation
of Al.
Amalgamation is one method frequently used to enhance
the activation of Al by using mercury or low melting point
metals as alloy elements. For example, mercury can moisten
the surface of Al and destroy the surface oxide layer.12,13)
However, mercury is very toxic. Low melting point metals
including Ga, In, Sn, Zn, Bi etc. can be doped in Al to obtain
the active alloys with high hydrolysis activity even at room
temperature in different water types.14) The liquid eutectic
effect of Al and low melting point metals was ascribed to
the enhancement of Al hydrolysis activity. Generally the
hydrolysis activity of Al alloys is related to the mass fraction
of low melting point metals.14­18) The high activity was
obtained when the mass fraction of low melting point metal
reaches 10­30%, which may greatly increase the cost of
active Al.
Other additives including oxide, salt, and carbon materials
were also employed to improve the hydrolysis activity of
Al.19­27) Babak Alinejad et al.19) reported a novel method to
fabricate Al nanoparticles using NaCl salt as additives by
milling. The highest average hydrogen generation rate can
reach 75 mL/min per 1 g Al in pure water at 70°C.
Furthermore, the activated powder can be easily stored for
a long time.20) Czech et al.21) investigated the effect of
different salt on the corrosion rate of Al powder. Using KCl
obtained the higher hydrogen generation rates and hydrogen
conversion efficiency in comparison with NaCl. Fan et al.22)
discussed the reactivity of Al­Bi alloys in water by adding
different salts including KCl, NaCl, LiCl, MgCl2, AlCl3. The
addition of MgCl2 exhibited a better effect than the other salts
in improving the reactivity of Al. Wang et al.23) has studied
different metal oxides nanocrystals including TiO2, Co3O4,
Preparation and Hydrolysis of Aluminum Based Composites for Hydrogen Production in Pure Water
Cr2O3, Fe2O3, Mn2O3, NiO, CuO and ZnO as additives to Al
powders for hydrogen generation in pure water at room
temperature. TiO2 nanocrystals were found to be highly
effective for hydrogen generation. Other additives such as
Al2O3,24,25) Al(OH)3,26) NaAlO227) were also investigated.
Unlike Al alloys activated by low melting point metals, Al
based composites prepared by addition of salts or oxides have
the merits of low cost. However, its hydrolysis activity may
be much lower than Al alloys, especially in pure water at
room temperature.
In this study, we aimed to find an effective way to produce
active Al materials for hydrogen generation with high rate
and low cost. Starting from Al­CaO system, we further added
NaCl salt and low melting point metals Ga, In, and Sn to
obtain the Al alloys-CaO­NaCl composites. The total amount
of Ga, In, and Sn was controlled within a very low content.
Therefore, both merits of high activity and low cost for alloy
elements and salt additives may be inherited in the newly
developed Al alloys-CaO­NaCl composites.
2.
Fig. 1 Effect of CaO additive on hydrogen yields for Al­CaO composites
in water at 60°C.
Table 1 Compositions of Al­CaO composites and its hydrolysis properties
in pure water.
Experimental Procedure
No.
Al powder (200 mush, 99 mass%) was used as starting
material. CaO (1250 mush, 98 mass%), NaCl (400 mush,
99.5 mass%), Ga (99.8 mass%), In (200 mush, 99 mass%),
and Sn (200 mush, 99 mass%) were employed as additives.
To prepare Al based composites, Al powder and additives
with total mass 20 g were mixed in an argon-filled glove box
at first. Then the mixtures were transferred to the QM-3SP2
planetary ball miller. The ball-to-powder ratio was set as
10 : 1. The milling time and rotation speed were performed
for 8 h and 360 r/min, respectively. The as-prepared products
were stored in argon-filled specimen bottles in order to avoid
oxidation.
Hydrolysis reaction was carried out in a 500 mL threenecked bottle. For each test, 1 g of as-prepared products was
added into 300 mL pure water in the three-necked bottle. The
temperature of water was controlled at 25°C or 60°C in order
to evaluate the influence of temperature on the hydrolysis
activity of Al based composites. Hydrogen gas was collected
through drainage method. The hydrogen conversion efficiency of Al based composites was calculated as follows:
E¼
Y
100%
ðw%=27Þ 1:5 24:45
ð1Þ
Where E is the conversion efficiency of hydrolysis reaction, Y
is the actual hydrogen yields (unit-L), w is the mass fraction
of Al in composites, 24.45 (unit-L) is the standard volume of
1 mol hydrogen gas at 25°C and 1 atm.
The phase structure identification was carried out on a XD2 type X-ray diffractometer with Cu K¡1 radiation (Beijing
Purkinje General Co. Ltd.). The step size was set as 0.02°/
step and time per step was 1.2 s/step. The microstructure
of Al based composites was recorded using JSM-6390LV
scanning electron microscope (SEM) with EDX analysis.
3.
Results and Discussions
3.1 Effect of CaO additive
Figure 1 shows the hydrogen yields for Al­CaO compo-
893
Element composition
(mass%)
Hydrogen yields
(V/mL)
Conversion efficiency
(%)
Al
Cao
1­1
97
3
10
0.78
1­2
1­3
95
93
5
7
33
72
2.55
5.69
1­4
91
9
110
8.89
sites in pure water at 60°C. The detailed mass fraction of CaO
additive varies from 3 to 9%, as shown in Table 1. It can be
observed that the hydrolysis activity of Al­CaO composites
in pure water is very low. The total hydrogen yields for Al­
CaO composites change from 10 to 110 mL with the increase
of CaO mass fraction from 3 to 9%, which are far below the
theoretical value (1358 mL) for 1 g Al reacting with water
completely at 25°C and 1 atm. The corresponding conversion
efficiency changes from 0.76 to 8.89%.
It is known that CaO is a kind of basic oxide which can
react with water to produce Ca(OH)2. For the low solubility
of Ca(OH)2 in water, a small amount of hydroxyl ions (OH¹)
is formed in pure water which may damage the surface oxide
layer of Al and promote the hydrolysis reaction. However,
hydrogen generation isn’t observed for Al­CaO composites
in pure water at 25°C, indicating the electrochemical
properties of Al­CaO composites are intimately related to
the temperature. Although the mass fraction of CaO additives
can be raised to enhance the hydrogen yields, the hydrogen
storage weight density of Al­CaO composites which can
be calculated from eq. (2) may decrease rapidly for the
reduction of effective Al mass fraction in composites.
D¼
mH2
100%
mc þ mH2 O
ð2Þ
Where D is the hydrogen storage weight density, mH2 is the
mass of hydrogen generated, mc is the mass of Al­CaO
composites, and mH2 O is the mass of water consumed in the
hydrolysis reaction. Therefore, the mass fraction of CaO
additives is controlled below 9%.
894
H. Wang et al.
(a)
(b)
Fig. 2 Effect of NaCl salt additive on hydrogen yields for Al­CaO­NaCl composites in water at 25°C (a) and 60°C (b).
Table 2 Compositions of Al­CaO­NaCl composites and its hydrolysis
properties in pure water.
No.
Element composition
(mass%)
Hydrogen yields
(V/mL)
Conversion efficiency
(%)
Al
CaO
NaCl
25°C
60°C
25°C
60°C
2­1
91
0
9
0
270
0
21.82
2­2
88
9
3
9
225
0.75
18.8
2­3
86
9
5
35
435
2.99
37.20
2­4
84
9
7
55
515
4.81
45.08
2­5
82
9
9
68
595
6.10
53.35
3.2 Effect of NaCl salt additive
In order to further enhance the activity of Al based
composites, NaCl salt was added to Al­CaO materials.
The mass ratio of different components in Al­CaO­NaCl
composites can be seen in Table 2. In contrast to Al­CaO
materials, the hydrogen yields in pure water at 25°C are
observed for Al­CaO­NaCl composites, as shown in
Fig. 2(a). The hydrogen conversion efficiency can reach
6.10% for Al­9%CaO­9%NaCl. Simultaneously, the hydrolysis activity of Al­CaO­NaCl composites is significantly
enhanced in pure water at 60°C, as shown in Fig. 2(b). With
the increase of NaCl salt mass fraction from 3 to 9%, the total
hydrogen yields and conversion efficiency vary from 225 to
595 mL and 18.8 to 53.35%, respectively.
For comparison, Al­9%NaCl was also produced and its
hydrolysis property was examined in pure water at 25 and
60°C, respectively (See Fig. 2 and Table 2). It can be found
that Al­9%CaO­NaCl has a higher generation rate than Al­
9%NaCl material. When the mass fraction of NaCl salt is
higher than 3%, the total hydrogen yields of Al­9%CaO­
NaCl are enhanced obviously.
It has been studied that NaCl salt particles can chop Al
particles into pieces during milling process. Furthermore,
NaCl salt particles are driven into the newly created surface
of Al and prohibit the aggregation of Al particles. During
hydrolysis, NaCl salt particles are dissolved in water
environment. As a result, the fresh Al surfaces will be
exposed to water and the hydrolysis proceeding is
promoted.19) Combined with the promotion role of CaO
additives, the higher hydrolysis activity of Al­CaO­NaCl
composites is obtained compared with that of Al­CaO and
Al­NaCl materials.
3.3 Effect of low melting point metal
In order to investigate the synergistic roles of low melting
point metals with CaO and NaCl, Al alloys-CaO­NaCl
composites were prepared, as shown in Table 3. For
comparison, both mass fractions of CaO and NaCl additives
were fixed as 9%. It is expected that the hydrolysis activity of
Al­9%CaO­NaCl% in pure water can be further improved
after the Al part in composites are doped with low melting
point metals to form Al alloys component. To study the effect
of different alloy elements on the hydrolysis activity of
composites, ternary and quaternary Al alloys (Al­In­Sn and
Al­Ga­In­Sn) with different mass fraction of Ga, In, and Sn
have been prepared.
Figure 3 shows the hydrogen yields of ternary Al alloys9%CaO­9%NaCl composites in pure water. In contrast to
Al­9%CaO­9%NaCl composite, the hydrolysis activity of
ternary Al alloys-9%CaO­9%NaCl composites are enhanced
greatly. When the mass ratio of In : Sn is set as 1 : 3, the total
hydrogen yields of Al alloys-9%CaO­9%NaCl composite in
pure water at 25°C reaches 410 mL in 2 h with 38.3%
conversion efficiency. When the temperature of pure water
increases to 60°C, the conversion efficiency gets to 92.75%,
which is near to the complete reaction between Al and water.
Furthermore, it can be found that the hydrolysis activity is
highly related to the mass ratio of In to Sn in composites. Al
alloys-9%CaO­9%NaCl composite with mass ratio 1 : 3 has
the highest activity in contrast to the other two composites
with mass ratio 3 : 1 and 2 : 2. The experimental results also
demonstrate that the ternary Al alloys-9%CaO­9%NaCl
composites possess the higher conversion efficiency than
the pure ternary Al alloy (Al­1%In­3%Sn), as shown in
Table 3 and Fig. 3.
Figure 4 shows the hydrogen yields of quaternary Al
alloys-9%CaO­9%NaCl composites. It can be seen that Al
based composite with mass ratio 1 : 1 : 2 (Ga : In : Sn) has
the highest activity in pure water among all the samples
prepared in this experiment. The hydrogen yields and
conversion efficiency in pure water at 60°C is 1026 mL and
95.84%, respectively.
3.4 Characterization
Figure 5 shows the XRD patterns of ternary Al alloys9%CaO­9%NaCl composites. All samples contain the
crystalline Al and NaCl phases. It is interesting that the
diffraction peak of CaO additive isn’t found in the patterns,
Preparation and Hydrolysis of Aluminum Based Composites for Hydrogen Production in Pure Water
Table 3
No.
895
Compositions of Al alloys-CaO­NaCl composites and its hydrolysis properties in pure water.
Element composition (mass%)
Hydrogen yields (V/mL)
Conversion efficiency (%)
Al alloys
CaO
NaCl
25°C
60°C
25°C
60°C
3­1
100
ðAl : ln : Sn ¼ 96 : 1 : 3Þ
0
0
160
162
11.77
11.91
3­2
82
ðAl : ln : Sn ¼ 96 : 3 : 1Þ
9
9
140
832
13.08
77.71
9
9
275
965
25.69
90.14
9
9
410
993
38.30
92.75
3­3
3­4
82
ðAl : ln : Sn ¼ 96 : 2 : 2Þ
82
ðAl : ln : Sn ¼ 96 : 1 : 3Þ
3­5
100
ðAl : Ga : ln : Sn ¼ 96 : 1 : 1 : 2Þ
0
0
122
200
8.97
14.71
3­6
82
ðAl : Ga : ln : Sn ¼ 96 : 1 : 2 : 1Þ
9
9
280
958
28.15
89.48
3­7
82
ðAl : Ga : ln : Sn ¼ 96 : 1 : 1 : 2Þ
9
9
421
1026
39.32
95.84
(a)
(b)
Fig. 3 Effect of In : Sn mass ratio on hydrogen yields for ternary Al alloys-9%CaO­9%NaCl composites in water at 25°C (a) and
60°C (b).
(a)
(b)
Fig. 4 Effect of Ga : In : Sn mass ratio on hydrogen yields for quaternary Al alloys-9%CaO­9%NaCl composites in water at 25°C (a) and
60°C (b).
while Ca(OH)2 phase is obtained which may be attributed to
the reaction of CaO with water vapor in air. Except these
phases, two intermetallic compounds In3Sn and InSn4 are
observed. For ternary Al alloys-9%CaO­9%NaCl composites, the mass ratio of In : Sn may affect the relative amount
of In3Sn and InSn4 in composites. The relative higher
diffraction peak intensity of In3Sn phase is observed in
Al alloys-9%CaO­9%NaCl composites (Al : In : Sn ¼
96 : 1 : 3), while the higher diffraction peak intensity of
InSn4 is found in Al alloys-9%CaO­9%NaCl composites
(Al : In : Sn ¼ 96 : 3 : 1), as shown in Fig. 5(b). No single In
or Sn phase is detected in the patterns. In our previous study, it
has been supposed the hydrolysis activity of Al alloys are
related to the amount and distribution of intermetallic
compounds In3Sn and InSn4.14) The difference on hydrolysis
activity of Al alloys-9%CaO­9%NaCl composites in this
experiment may be ascribed to its phase compositions.
The XRD patterns of quaternary Al alloys-9%CaO­9%NaCl
composites are similar as Fig. 5 (not shown here). Ga phase is
not observed in the patterns for its low amount. Similar
phenomenon is also observed in Al alloys even with high Ga
amount in our previous study and the other literatures.14,16,18)
896
H. Wang et al.
(a)
(b)
Fig. 5 X-ray diffraction patterns of ternary Al alloys-9%CaO­9%NaCl composites (a) and the corresponding characterized diffraction
peaks of In3Sn and InSn4 (b).
(a)
(b)
(c)
(d)
Fig. 6 SEM images of Al­9%CaO (a), Al­9%CaO­9%NaCl (b), ternary Al alloys-9%CaO­9%NaCl (In : Sn ¼ 1 : 3) (c), and quaternary
alloys-9%CaO­9%NaCl (Ga : In : Sn ¼ 1 : 1 : 2) composites (d).
Figure 6 presents the SEM images of Al­9%CaO, Al­
9%CaO­9%NaCl, ternary Al alloys-9% CaO­9% NaCl
(Al : In : Sn ¼ 96 : 1 : 3), and quaternary Al alloys-9%CaO­
9% NaCl (Al : Ga : In : Sn ¼ 96 : 1 : 1 : 2). It can be seen
that many pits and breaks are formed in all samples after
mechanical milling process, which may increase more
specific exposed surface of Al to water. In contrast to Al­
9%CaO (Fig. 6(a)), many regular particles are observed and
homogeneously distributed on the surface of the other three
samples (Figs. 6(b), 6(c) and 6(d)). For Al­9%CaO­9%NaCl
composite, it seems that the particles are attached on the
surface of Al without driving into Al matrix (Fig. 6(b)).
However, these particles are inserted inside the matrix of Al
alloys-9%CaO­9% NaCl composites.
In order to examine the element compositions of these
particles, EDS spot scanning is used to study the element
compositions in designed fields, as shown in Fig. 7 and
Table 4 Element compositions in designed fields of Al­9%CaO and Al­
9%CaO­9%NaCl composites.
Sample
Al­9%Cao
Al­9%CaO­9%Nacl
Spectrum
Element (mass%)
Al
Na
Cl
Ca
O
Spot 1
49.43
0
0
4.72
45.85
Spot 2
49.89
0
0
4.10
46.01
Spot 3
50.20
0
0
3.68
46.12
Spot 1
46.70
4.85
3.79
2.37
43.28
Spot 2
44.11
5.50
4.81
3.17
42.41
Spot 3
46.47
4.00
3.53
2.35
43.66
Table 4. For comparison, Al­9%CaO and Al­9%CaO­
9%NaCl composites are analyzed especially the special
particles on the surface of Al­9%CaO­9%NaCl composite,
as shown in spot 1 and 2 in Fig. 7(b). It can be seen that the
Preparation and Hydrolysis of Aluminum Based Composites for Hydrogen Production in Pure Water
Fig. 7
897
EDS spectra in designed fields of Al­9%CaO (a) and Al­9%CaO­9%NaCl composites (b).
Fig. 9
Fig. 8 X-ray diffraction patterns of hydrolysis products for Al based
composites.
compositions of regular particles mainly consists of element
Na and Cl. As there are no such regular particles appearing
on the surface of Al­9%CaO composite, it is suggested that
the regular particles distributed on the surface of the other
three composites are NaCl salt.
Furthermore, it is shown in Fig. 6 that the size of NaCl salt
particles in Al alloys-9%CaO­9%NaCl composites is much
smaller than that in Al­9%CaO­9%NaCl composite. According to Rebinder’s effect, the addition of low melting point
metals will lead to the embrittlement of Al.15) Therefore, the
interaction force between NaCl salt particles and Al powder
is enhanced during mechanical milling process. NaCl salt
particles are broken into several small pieces and inserted
into the breaks and Al matrix.
Figure 8 displays the XRD patterns of the hydrolysis
products of Al based composites in pure water. As the
hydrogen conversion efficiency of Al­9%CaO and Al­
9%CaO­9%NaCl composites is very low, the mainly phase
of products is Al. However, the diffraction peak intensity of
Al is negligible in the hydrolysis products of Al alloys9%CaO­9%NaCl composites. The mainly hydrolysis products are composed of Al(OH)3 and AlO(OH). The diffraction
peaks of Al(OH)3 are sharp, while the peaks of AlO(OH) are
wide indicating its low crystalline.
Proposed reaction mechanism of Al based composites in water.
3.5 Proposed mechanism
From the above results, it can be seen that there is a
synergistic role of CaO, NaCl salt and low melting point
metals additives on improving the hydrolysis activity of Al
based composites. By adjusting the mass ratio of different
components, the morphology and phase compositions of
Al based composites can be effectively tuned, thus the
hydrolysis activity and products of Al based composites are
quite different.
Basically, the aluminum hydrolysis reaction related to
hydrogen yields can be expressed as follows:
2Al þ 4H2 O ! 2AlOðOHÞ þ 3H2
ð3Þ
or 2Al þ 6H2 O ! 2AlðOHÞ3 þ 3H2
ð4Þ
Both two hydrolysis products are found in this experiment.
Considering the different components of Al based composites, the microstructure related hydrolysis reaction mechanism is proposed in Fig. 9.
As NaCl salt particles have sharp edges and are stiffer than
Al powder, they are driven into Al matrix and destroy the
surface oxide layer during the high energy ball milling
process. These NaCl salt particles are homogeneously
distributed on the surface of composites and form the salt
gates. In water environment, these salt gates are exposed to
water and become the active spots. More salt gates are
produced the higher activity of composites are obtained.
As Al alloys-9%CaO­9%NaCl composites have more tiny
and small NaCl salt particles than Al­9%CaO­9%NaCl
898
H. Wang et al.
material, the higher hydrogen yields and conversion
efficiency are observed. With the increase of water temperature from 25 to 60°C, the dissolution rate of NaCl salt
particles in water is accelerated, which leads to the
dissolution of salt gates rapidly and completely. Therefore,
the hydrolysis reaction is enhanced. The hydrolysis reaction
mechanism of the composites based on salt gates follows the
eq. (3). The hydrolysis products are mainly composed of
AlO(OH), which has been discussed in literature.19)
On the other hand, CaO additives in composites are also
dissolved in water environment during hydrolysis reaction as
follows:
CaO þ H2 O ! Ca2þ þ 2OH
ð5Þ
The hydroxyl ions acting as the catalyst for the hydrolysis of
Al promotes the hydrogen generation. More CaO additives in
composites will lead to the formation of higher amount of
hydroxyl ions. Therefore, more hydrogen yields are obtained.
Under this condition, the hydrolysis reaction mechanism
follows the eq. (4). In a conclusion, both two reactions (3)
and (4) proceed in the hydrolysis of Al based composites in
this experiment, which may be corresponding to two different
activation modes.
4.
Conclusion
The preparation and hydrolysis activity of Al based
composites using CaO, NaCl salt and low melting point
metals (Ga, In, Sn) as additives were investigated in this
work. The Al alloys-CaO­NaCl composites exhibited the
higher hydrolysis yields than Al­CaO and Al­CaO­NaCl
composites in pure water. It was proposed that the synergistic
role of low melting point metals, CaO and NaCl salt are
attributed to the improvement of hydrolysis activity. Low
melting point metals (Ga, In, Sn) leads to the embrittlement
of Al. NaCl salt particles are driven into Al matrix and
destroy the surface oxide layer. CaO additives dissolve in
water and produce hydroxyl ions. Therefore, all additives
promote the hydrolysis reaction of Al and water. The
hydrolysis products of Al based composites in this experiment mainly consist of AlO(OH) and Al(OH)3, which is
corresponding to two different reaction paths.
Acknowledgements
The authors gratefully acknowledge the financial support
of National Natural Science Foundation of China (No.
51202064), Natural Science Foundation of Hubei Province of
China (No. 2013CFA085), Outstanding Youth Talent Project
of Hubei Provincial Department of Education (No.
Q20121401), and Major State Basic Research Development
Program of China (973 Program, 2010CB635107).
REFERENCES
1) L. Barreto, A. Makihira and K. Riahi: Int. J. Hydrogen Energy 28
(2003) 267­284.
2) A. Mahecha-Botero, T. Boyd, A. Gulamhusein, J. R. Grace, C. J. Lim,
Y. Shirasaki, H. Kurokawa and I. Yasuda: Int. J. Hydrogen Energy 36
(2011) 10727­10736.
3) E. Shoko, B. McLellan, A. L. Dicks and J. C. Diniz da Costa: Int. J.
Coal. Geol. 65 (2006) 213­222.
4) D. Trommer, F. Noembrini, M. Fasciana, D. Rodriguez, A. Morales, M.
Romero and A. Steinfeld: Int. J. Hydrogen Energy 30 (2005) 605­618.
5) S. K. Mazloomi and N. Sulaiman: Renew. Sustain. Energy. Rev. 16
(2012) 4257­4263.
6) K. Zeng and D. Zhang: Prog. Energy Combust. Sci. 36 (2010) 307­
326.
7) G. W. Michael, L. W. Emily, R. M. James, W. B. Shannon, Q. Mi and
A. S. Elizabeth: Chem. Rev. 110 (2010) 6446­6473.
8) E. Kirtay: Energy Convers. Manage. 52 (2011) 1778­1789.
9) X. Huang, T. Gao, X. Pan, D. Wei, C. Lv, L. Qin and Y. Huang:
J. Power Sources 229 (2013) 133­140.
10) H. Zou, S. Chen, Z. Zhao and W. Lin: J. Alloy. Compd. 578 (2013)
380­384.
11) A. A. El-Meligi: Int. J. Hydrogen Energy 36 (2011) 10600­10607.
12) J. B. Bessone: J. Corros. Sci. 48 (2006) 4243­4256.
13) X. Huang, C. Lv, Y. Huang, S. Liu, C. Wang and D. Chen: Int. J.
Hydrogen Energy 36 (2011) 15119­15124.
14) H. Wang, Y. Chang, S. Dong, Z. Lei, Q. Zhu, P. Luo and Z. Xie: Int. J.
Hydrogen Energy 38 (2013) 1236­1243.
15) A. V. Parmuzina and O. V. Kravchenko: Int. J. Hydrogen Energy 33
(2008) 3073­3076.
16) O. V. Kravchenko, K. N. Semenenko, B. M. Bulychev and K. B.
Kalmykov: J. Alloy. Compd. 397 (2005) 58­62.
17) M. Fan, F. Xu and L. Sun: Int. J. Hydrogen Energy 32 (2007) 2809­
2815.
18) A. V. Ilyukhina, A. S. Ilyukhin and E. I. Shkolnikov: Int. J. Hydrogen
Energy 37 (2012) 16382­16387.
19) B. Alinejad and K. Mahmoodi: Int. J. Hydrogen Energy 34 (2009)
7934­7938.
20) K. Mahmoodi and B. Alinejad: Int. J. Hydrogen Energy 35 (2010)
5227­5232.
21) E. Czech and T. Troczynski: Int. J. Hydrogen Energy 35 (2010) 1029­
1037.
22) M. Fan, F. Xu, L. Sun, J. Zhao, T. Jiang and W. Li: J. Alloy. Compd.
460 (2008) 125­129.
23) H. Wang, H. Chung, H. Teng and G. Cao: Int. J. Hydrogen Energy 36
(2011) 15136­15144.
24) Z. Y. Deng, Y. F. Liu, Y. Tanaka, J. H. Ye and Y. Sakka: J. Am. Ceram.
Soc. 88 (2005) 977­979.
25) Z. Y. Deng, Y. F. Liu, Y. Tanaka, H. W. Zhang, J. H. Ye and Y. Kagawa:
J. Am. Ceram. Soc. 88 (2005) 2975­2977.
26) J. Skrovan, A. Alfantazi and T. Troczynski: J. Appl. Electrochem. 39
(2009) 1695­1702.
27) H. Soler, A. M. Candela, J. Macanás, M. Muñoz and J. Casado: Int. J.
Hydrogen Energy 34 (2009) 8511­8518.