Advances in Materials Physics and Chemistry, 2013, 3, 295-298
Published Online November 2013 (http://www.scirp.org/journal/ampc)
Open Access AMPC
An Approach on the Hydrogen Absorption in Carbon
Black after Gamma Irradiation
Antonio Madroñero1, Mario Culebras2, Andrés Cantarero2, Clara M. Gómez2, César Mota1,
José M. Amo1, José I. Robla1
1Centro Nacional de Investigaciones Metalúrgicas (CSIC), Madrid, Spain
2Instituto de Ciencia de los Materiales, Universidad de Valencia, Valencia, Spain
Email: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com,
firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
Received August 25, 2013; revised September 28, 2013; accepted October 14, 2013
Copyright © 2013 Antonio Madroñero et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
In this work, different samples of an industrial carbon black are used to study the hydrogen intake from an over pres-
surized atmosphere and its changes due to alteration of its level of crystallinity produced by γ-irradiation. The monitor-
ing of the hydrogen adsorption was made by means of thermogravimetric analysis and by measurements of some elec-
trical parameters as the Seebeck coefficient. X-ray diffraction shows that the irradiation diminishes the level of crystal-
line perfection. These results show interesting possibilities to use carbon black as cheap hydrogen absorbers.
Keywords: Carbon Black; Hydrogen Storage; Carbon Semiconductor; Seebeck’s Effect; Gamma Irradiation
As it is well known, hydrogen plays a double role in
carbons when the carbons store hydrogen showing elec-
trical parameters figures that correspond to semiconduc-
tor materials . As a result, to increase the hydrogen
storage capability of carbons is a good path to obtain
cheap semiconducting carbons. As the hydrogen intake
starts in the surface of the solids, many works were ori-
ented to the improvement of the surface paying attention
to the optimization of the hydrogen adsorption. Follow-
ing this direction, as it is commonly accepted, the amount
of defects and the distribution and sizes of them were the
main parameters to achieve a good hydrogen adsorption.
The linear relationship between the hydrogen uptake and
the specific surface area (SSA) is independent of the na-
ture of the carbon material . In the development of
carbonaceous absorbers for hydrogen storage there are
many studies showing different techniques to activate the
carbon’s surface, with chemicals  and with gas etching
. Most of the commercial active carbons available
nowadays to store hydrogen correspond to this stage.
After that, the possibility was explored to use physical
treatments to produce the required defects. Radiation by
γ-rays is a powerful tool to produce defects in the surface
and inner defects in carbons .
In carbon nanotubes, γ-irradiation had been more ef-
fective than chemical etching to activate carbon surfaces
. In the present work, we will study the capability of
γ-rays to increase the semiconducting character of carbon
black samples to increase the hydrogen absorption.
The material used in the present work was from Black
Pearls 1400, manufactured by Cabot™. According to the
manufacturer’s information, the specific surface of this
material is 560 m2/g. We have selected carbon black
specimens with the best performance. The surface energy
of commercial carbons blacks is from 70 - 200 m2/g 
and the figure of the surface area is a liable identifier of
carbons with a good capacity for hydrogen adsorption .
The samples were subjected to two successive treatments:
hydrogenation and irradiation. The hydrogenation was
performed in a pressurize hydrogen atmosphere at 20 bar
and room temperature for 180 minutes. In these condi-
tions, a hydrogen adsorption on the carbon black powder
took place. The used hydrogen was Ultrapure Plus ×50S
(99.9992%), supplied by Carburos Metalicos™. In the
irradiation process, the sample was exposed to a 504-kGy
irradiation with 60Co isotopes. The sample exposure to
the radioisotopes was carried out by immersion in a wa-
A. MADROÑERO ET AL.
ter well where the radioisotopes were located. The loca-
tion was the Nayade facility, existing at the Centre of
Energy, Environment and Technology Research (Centro
de Investigaciones Energéticas, Medioambientales y
Tecnólogicas, CIEMAT), in Madrid, Spain.
For this study, four samples are prepared in order to
study hydrogenation and irradiation effects in the sam-
ples as summarized in Table 1.
3.1. Thermogravimetrical Analysis
The four samples analysed here were examined by Ther-
mal Gravimetry (TGA), using the equipment DTA/TGA
SETARAM Setsys Evolution. The weight of the four
samples was around 13 mg.
The measurement supposed a heating from room tem-
perature to 1073 K in an argon atmosphere (20 ml/min).
The heating rate for the four samples was:
1) From room temperature up to 673 K: the heating
rate was 5 K/min.
2) From 673 K up to 873 K: the heating rate was 3
3) From 873 K to 1073 K: the rate was 5 K/min.
The TGA curves were recorded using the software
3.2. X-Ray Diffracti on
Another technique of examination was X-Ray Diffrac-
tion (XRD), performed in a Siemens D5000 diffractome-
ter with Ni-filtered Cu Kα radiation. The X-ray tube was
operated at 40 kV and 30 mA. The experimental diffrac-
tometers were collected with a step of 0.03˚ (2θ) and an
averaging time of 0.6˚/min. The XRD patterns of the
samples were identified with the Joint Committee on
Powder Diffraction Standards (JCPDS) files.
3.3. Electrical Parameters Measurements
The samples were compacted in thin pellets and four
contacts with silver paste were deposited on the surface
for electric characterization. In order to measure the elec-
trical conductivity, the Van der Pauw method was used
. The electrical conductivity can be obtained solving
Table 1. Treatments in the carbon black samples.
TN-sH without treatment
CN-H Irradiation and hydrogenation
the Van der Pauw equation:
To calculate R1 and R2 four contacts, labelled A, B, C
and D, were used. R1 is obtained as 1
RV I and
, were V and I are the voltage and intensity
across the sample, respectively. A Keithley 2400 mul-
timeter was used as a current source.
The Seebeck coefficient is determined as the ratio be-
tween the electrical potential, , and the temperature
, that is:
For the temperature control, a “Lakeshore 340 Tem-
perature Controller” was used and for recording the po-
tential data a “Keithley 2750 Data Acquisition Switching
4. Results and Discussion
Figure 1 shows the results of the TGA. The more rele-
vant feature in sample CN-H is that there is an increase
in weight, more pronounced at temperatures about 500 -
700 K. It is easy to explain it as a process of argon ab-
sorption [10,11] that takes place in the surface of the car-
bonaceous materials. In samples TN-H, CN-sH and TN-
sH, Ar adsorption at the sample surface was not ob-
On the other hand, in Tabl e 2, the weight loss, a pa-
rameter that supplies information about the hydrogen
storage I shown. It is simple to see that the irradiated
samples stores more hydrogen that the non-irradiated
ones. A figure of hydrogen content larger than 10% w/w
has interest looking at the possibility of use carbon
blacks as cheap hydrogen adsorbers in other fields of the
hydrogen economy as in the construction of portable can-
ister with stored hydrogen for the automotive industry.
In Figure 2, referred to non-hydrogenated samples, it
300 400 500 600 700 800 90010001100
300 400 500 600 700 800 90010001100
Figure 1. Thermal gravimetric analysis of the samples.
Open Access AMPC
A. MADROÑERO ET AL. 297
020 40 60 80100120
2 Theta (degrees)
Figure 2. XRD plot of non-hydrogenated sample s.
Table 2. Weight loss (in %) during the TGA showing the
variations in the different temperature ranges.
Δm1 (%) Δm2 (%) Δm3 (%)
(273 - 673 K) (673 - 873 K) (873 - 1073 K)
CN-H 1.596 −9.877 −10.444 −18.69
CN-sH −1.184 −2.826 −2.329 −13.0
TN-H −7.167 −2.839 −2.219 −12.11
TN-sH −8.338 −2.723 −1.987 −13.0
is possible to see that the effect of the irradiation is to
diminish the crystalline perfection displayed as an im-
pairing of the slenderness of the diffraction peak; the
irradiated carbon black becomes more similar to an
amorphous sample. The fact that γ irradiation increases
the hydrogen intake in carbon materials is in agreement
with the knowledge that amorphous carbons are better
absorbers than crystalline carbons .
Similar results are obtained in Figure 3 for the hydro-
genated samples. Actually, the diffraction is a powerful
tool to distinguish between irradiated and non-irradiated
materials, but not very reliable to evaluate the level of
In the same way, if we proceed to evaluate the crystal-
line size Lc using the Scherrer’s formula , as shown
in Table 3, the effect of the irradiation is to diminish Lc.
Similar evolution of XRD is known in carbon nano-
tubes irradiated with γ-rays .
The electrical properties of the samples have been ob-
tained using the Van der Paw’s technique described
above and the results are shown in Table 4, where it is
possible to see that the absorption of hydrogen decreases
the electrical conductivity, as, it is known for similar
The influence of the irradiation process is effective
regarding the change in Seebeck’s coefficient. In Table 4
we can observe that the irradiation per se improves the
2 Theta (degrees)
Figure 3. XRD plot of hydrogenated samples.
Table 3. Determinati on of cryst alline size usi ng the Scherrer’s
Sample L [Å]
Table 4. Results of the measurements of electric conductiv-
ity and Seebeck’s effect of the carbon black samples.
Sample σ (S/cm) S (μV/K)
TN-sH 2.00 0.87 ± 0.01
TN-H 1.49 4.2 ± 0.2
CN-sH 1.41 2.63 ± 0.05
CN-H 1.09 3.25 ± 0.05
Seebeck’s coefficient, but it is also remarkable that the
intake of hydrogen increases that coefficient.
According to the above results, it is possible to conclude
that the use of previous γ-irradiation improves the hy-
drogen intake at room temperature in carbon black from
an over-pressurized atmosphere. The carbon black is
converted into a more amorphous material by the effect
of the irradiation. The X-ray diffraction is a valid tech-
nique to observe the changes that take place in the carbon
black as a consequence of γ-irradiation and the alteration
in the crystalline structure is explained by the change in
the lattice parameter Lc.
We would like to acknowledge support from the Spanish
Open Access AMPC
A. MADROÑERO ET AL.
Open Access AMPC
Ministry of Finances and Competitivity (MINECO),
through the grant of the Consolider-Ingenio 2010 project
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