Appl Phys A
DOI 10.1007/s00339-013-7697-0
Effect of electrochemical treatment on structural properties
of conical carbon nanotubes
S.M. Khantimerov · V.A. Shustov · N.V. Kurbatova ·
E.F. Kukovitsky · V.L. Matukhin · Y.A. Sakhratov ·
N.M. Suleimanov
Received: 24 January 2013 / Accepted: 7 April 2013
© Springer-Verlag Berlin Heidelberg 2013
Abstract Interaction of multiwalled conical carbon nan-
otubes (CNTs) with hydrogen during their electrochemical
treatment was studied by galvanostatic measurements and
Raman spectroscopy. The structural changes occurring in
the conical walls of the CNTs in consequence of the hy-
drogenation were investigated by using X-ray diffraction
(XRD). The results obtained show that hydrogen sorption
by conical CNTs is reversible. XRD studies revealed that
the electrochemical hydrogenation leads to a change in the
diffraction peak profile (2θ = 26
◦
) and its position corre-
sponding to the interplanar distance in conical CNTs. The
results indicate structural changes occurring in the conical
walls of the CNTs during hydrogenation. We assume that
these structural changes can be caused by the hydrogen
intercalation into the interplanar spaces of conical CNTs.
Thus, the charge/discharge and structure data can be ex-
plained by the existence in this system of physically ad-
sorbed molecular hydrogen and chemically bound atomic
hydrogen.
1 Introduction
Carbon nanotubes (CNTs) have attracted considerable inter-
est as a material being expected in various applications such
S.M. Khantimerov () · V.A. Shustov · N.V. Kurbatova ·
E.F. Kukovitsky · N.M. Suleimanov
E.K. Zavoisky Physical-Technical Institute of Russian Academy
of Sciences, Sibirsky Trakt, 10/7, 420029 Kazan, Russia
e-mail: khantim@mail.ru
Fax: +7-843-2725075
S.M. Khantimerov · V.L. Matukhin · Y.A. Sakhratov ·
N.M. Suleimanov
Kazan State Power Engineering University, Krasnoselskaya, 51,
420066 Kazan, Russia
as catalyst supports, energy storage devices etc. [1, 2]. The
possibility of carbon nanostructures’ use for hydrogen stor-
age in the form of physically adsorbed molecules or chem-
ically bound atomic states is determined by several factors.
First, these materials have a significant specific surface area
(up to 2500 m
2
/g), which ensures their high sorption (ad-
or absorption) capacity. Secondly, when selecting a mate-
rial for hydrogen storage the amount of hydrogen sorbed per
unit of volume or weight of the container is of great impor-
tance [3]. Theoretically, CNTs can uptake up to 7.7 wt.%
of hydrogen. Thus, CNTs have a great potential in terms of
hydrogen sorption [4, 5]. However, the experimental results
obtained by this time differ from those estimated theoret-
ically especially if multiwalled carbon nanotubes (MWC-
NTs) are being used.
Thus, the use of carbon nanotubes for hydrogen storage
can be successfully realized no earlier than a number of fun-
damental problems associated with studies of hydrogen in-
teraction with carbon nanostructured materials are solved.
The investigation of new methods of hydrogenation, study-
ing of the electrolytic hydrogen intercalation into the car-
bon nanomatrix and formation of carbon–hydrogen bond
research are among these problems. A fundamental under-
standing of the mechanism of hydrogen interaction with the
surface of CNTs is needed. The possible mechanisms of
hydrogen sorption by CNTs are their physical or chemical
sorption by these structures. In the first case, the sorption
is due to physical adsorption of molecular hydrogen on the
walls of CNTs. Chemisorption is related to the dissociation
of hydrogen molecules after which hydrogen is attached to
an unsaturated C–C bond forming a C–H bond [6].
Carbon nanotube structures have as a rule a good elec-
trical conductivity, which allows the use of electrochemical
methods to study their interaction with hydrogen [7]. When
using the galvanostatic method a current density through the