Synthesis of carbon nanorods by reduction of carbon bisulfide

Article abstract of DOI:10.1016/j.jallcom.2010.07.097

Carbon nanorods are synthesized at large scale by the reduction of carbon bisulfide at 600 °C. Moreover, novel Y-junction carbon nanorods are detected in the samples. The X-ray power diffraction pattern indicates that the products are hexagonal graphite. Scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy and N₂ physisorption studies show that carbon nanorods predominate in the product. Based on the supercritical carbon bisulfide system, the possible growth mechanism of the carbon nanorods was discussed. This method provides a simple and cheap route to large-scale synthesis of carbon nanorods.

Full text of DOI:10.1016/j.jallcom.2010.07.097

Journal of Alloys and Compounds 507 (2010) 38–41
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jallcom
Synthesis of carbon nanorods by reduction of carbon bisulfide
∗
Zhengsong Lou , Minglong He, Dejian Zhao, Zhongchun Li, Tongming Shang
Laboratory of Precious Metal Processing Technology and Application, School of Applied Chemistry, Jiangsu Teachers University of Technology,
Yu Ying Road 2, Changzhou 213001, PR China
a r t i c l e i n f o
a b s t r a c t
◦
Article history:
Available online 17 July 2010
Carbon nanorods are synthesized at large scale by the reduction of carbon bisulfide at 600 C. More-
over, novel Y-junction carbon nanorods are detected in the samples. The X-ray power diffraction pattern
indicates that the products are hexagonal graphite. Scanning electron microscopy, transmission electron
microscopy, high-resolution transmission electron microscopy and N2 physisorption studies show that
carbon nanorods predominate in the product. Based on the supercritical carbon bisulfide system, the
possible growth mechanism of the carbon nanorods was discussed. This method provides a simple and
cheap route to large-scale synthesis of carbon nanorods.
Keywords:
Nanostructure
Chemical synthesis
N2 physisorption
Carbon nanorods
Scanning electron microscopy
X-ray diffraction
©
2010 Elsevier B.V. All rights reserved.
1
. Introduction
we report a method for synthesizing carbon nanorods on a large
scale using the reaction of carbon bisulfide with metallic lithium in
a stainless autoclave at 600 C. The reaction can be formulated as
◦
Carbon nanomaterials have attracted great interests in the
past decades, especially after the detection of fullerenes [1]. The
structures, texture and diversity of various carbon nanomaterials
such as carbon nanoparticles [2], nanotubes [3], carbon nanorods
follows:
CS2(g) + 4Li(l) → C(nanorods + graphite) + 2Li2S(s)
[
4], onions [5], nanowires [6] and nanofibers [7] were observed
We call this route the carbon bisulfide thermal reduction pro-
cess, in which carbon bisulfide is used as the carbon source and Li is
used as the reductant. Based on the field emission scanning electron
microscope and transmission electron microscope analysis, the car-
bon nanorods account for about 80% of the carbon product, and
the rest are graphite and amorphous carbon. In addition, various
shaped Y-junction carbon nanorods are also found in the product.
thereafter [1]. Understanding their properties and exploring their
promising application have led to a great increase of research
worldwide. The nano-meter carbon material is expected to behave
like semiconductor with relatively large band gap. For example, car-
bon nanoparticles are of interests not only for fundamental studies
of mechanical and electric properties, but also for various potential
applications such as fillers [8], high-performance electrode mate-
rials in batteries [9]. Carbon nanorods have largely been applied in
anodic materials of batteries because of their performance [10]. Up
to now, various methods have been demonstrated for the synthesis
of carbon nanorods, which include the arc discharge method [11],
the chemical vapor deposition [12], the template methods [13],
the electron beam-induced route [14] and the catalytic copyrolysis
method [15].
Recently, we have been focusing on the synthesis of diamond
and carbon-based materials by the reduction of carbon dioxide and
carbonate with alkali metals [16–19]. Because of similar chemical
and physical properties (polarity, supercritical phase, etc.) of car-
bon bisulfide and carbon dioxide, we tentatively try to synthesize
carbon materials by the reduction of carbon bisulfide. In this study,
2
.
Experimental
In this method, the reaction was carried out in a stainless steel autoclave (16 mL).
◦
If it is not specifically mentioned, most of the reactions were conducted at 600 C. In
a typical preparation, 12.0 mL CS2 and 1.2 g of metallic Li were used, and they were
placed in a stainless autoclave at room temperature. The vessel was then immedi-
ately closed tightly and heated up to 600 ◦C, and maintained at this temperature for
10 h. The reaction took place at an autogenic pressure depending on the reactant
amount added. After cooling down to room temperature, the solid product was col-
◦
lected and treated in 6.0 mol/L HCl aqueous solution at 80 C for 6 h to remove Li2S
and iron based materials from the autoclave. A microfilter was used to collect the
precipitate that was then washed with ethanol and dried in air, yielding about 0.49 g
of product.
The X-ray diffraction (XRD) analysis was performed using a Rigaku (Japan)
D/max-ꢀA X-ray diffractometer equipped with graphite monochromatized Cu K␣
radiation (ꢁ = 1.54178 A˚ ). The morphology of the samples was observed on a field
emission scanning electron microscope (FESEM) (JEOL-6300F, 15 kV). Transmission
electron microscopic (TEM) images and electron diffraction (ED) patterns were taken
on a Hitachi H-800 transmission electron microscope. The microstructure of car-
bon nanorods was analyzed by high-resolution transmission electron microscopy
(HRTEM), which was performed on a JEOL-2010 transmission electron microscope
∗ Corresponding author. Tel.: +86 519 6999842; fax: +86 519 6999516.
E-mail address: lzs@jstu.edu.cn (Z. Lou).
0
925-8388/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2010.07.097

Z. Lou et al. / Journal of Alloys and Compounds 507 (2010) 38–41
39
Fig. 1. XRD pattern of the products after treatment by HCl aqueous solutions.
using an accelerating voltage of 200 kV. N2 adsorption–desorption studies were car-
ried out at 77 K with a static volumetric instrument Autosorb-1 (Quantachrome)
to examine the porous properties of the sample. Samples were pretreated by out-
◦
gassing in vacuum at 200 C for at least 5 h, and the pore size distribution (PSD) was
evaluated from the desorption isotherms using the BJH method [20].
3
. Results and discussion
Fig. 1 shows the XRD pattern of the sample after treated with
.0 mol/L HCl aqueous solution. It contains characteristic diffraction
6
peaks, indexed with 0 0 2 and 1 0, respectively, which corresponds
to the hexagonal graphite phase (PDF cards, JCPDS 41-1487). More-
over, the broad (1 0) diffraction originates from a two-dimensional
lattice. It can also be conformed by the HRTEM image of the sample.
Figs. 2 and 3 are FESEM and TEM images of carbon nanorods,
respectively. The FESEM images show that there are large num-
bers of carbon nanorods in the sample, and the diameter of carbon
nanorods ranges from 40 nm to 140 nm. Fig. 2b is the enlarged
image of the rectangle area shown in Fig. 2a. Carbon nanorods can
be clearly seen, indicating the large quantity of carbon nanorods
obtained via this approach. The TEM images of the product reveal
that the diameter of carbon nanorods is about 40–150 nm, and the
lengths of carbon nanorods are in the range from hundreds of nano-
meters to several micrometers, which are in agreement with the
result of FESEM observations. Fig. 3a is a typical TEM image of the
carbon nanorods, and the selected area electron diffraction (SAED)
pattern of the nanorods shows a pair of small but strong arcs cor-
responding to (0 0 2) (in Fig. 3d). The broadening of the diffraction
ring is observed due to the rolling of graphitic layers. It should be
noted that appreciable amount of various shaped Y-junction car-
bon nanorods (∼10% based on TEM images) are observed in the
products, which are shown in Fig. 3b and c. The SAED pattern (in
Fig. 3e) of a junction of Y-like carbon nanorods exhibits four small
but strong arcs for 0 0 2, which imply the orientation of the 0 0 2
planes in the junction of carbon nanorods. The results suggest that
the junction is formed by the curvature caused by different carbon
rings. These observations are consistent with previous report [21].
A more detailed investigation of as-prepared products was car-
ried out by HRTEM. The HRTEM images show the irregular graphite
layers are almost perpendicular to electron beam and their inter-
layer spacing is about 0.34 nm, which is typical for the (0 0 2) lattice
distance in hexagonal carbon. These graphite layers typically form
multiwall structures and create complex morphologies, consisting
of the combination of straight domains, bent walls, and multiwall
circular shape (Fig. 4a and b).
Fig. 2. FESEM image of the as-prepared product: (a) FESEM image of carbon
nanorods and (b) the enlarged image of the rectangle area shown in (a).
The results of FESEM, TEM and N2 physisorption are com-
plementary with respect to probing the structural integrity of
the product. The images of FESEM and TEM can be used to
observe the subtle portion of the material while N2 physisorp-
tion gives a picture of the overall porosity of the material. The
N2 adsorption–desorption isotherm and PSD of the product are
presented in Fig. 5a and b. The isotherms of the sample appears typ-
ically in Type IV characteristic, according to the IUPAC classification,
with hysteresis loops initiating from the medium relative pressures
(P/P ∼ 0.40), and closing near P/P ∼ 1. BJH cumulative desorption
0
0
2
−1
surface area is 74.42 m g and BJH cumulative desorption pore
volume is 14.26 cm g
3
−1
.
Pore size distributions of the carbon nanorods can be seen
intuitively in Fig. 5b. The primary mesopores are found of a size
of around 3.9 nm, accompanied with pore size of 1.7 nm, 2.2 nm,
2.6 nm, 3.0 nm and 6.2 nm by desorption BJH method. In the light
of Cheng and coworkers research [22], there are more mesopores
corresponding to the size of 3–4 nm, which demonstrates the prod-
ucts might contain MWNT, but samples exhibit relatively low pore
volumes, these prove that the quantity of MWNT is small and main
products are carbon nanorods, it has been further confirmed by
FESEM and TEM results. There are no aggregated pores, which
demonstrate carbon nanorods conglomerate compactness as indi-
cated by FESEM image in Fig. 2.
The carbon nanorods with relatively high surface areas are
expected to have similar chemical properties of carbon nanotubes,
which might find potential applications such as catalyst carriers,
lubricants and hydrogen storage materials [23]. In addition, the car-

4
0
Z. Lou et al. / Journal of Alloys and Compounds 507 (2010) 38–41
Fig. 3. TEM micrographs of carbon nanorods: (a) TEM image of the typical carbon nanorods; (b and c) carbon nanorods with multiple Y-junctions; (d) selected area electron
diffraction pattern of the carbon nanorods; (e) selected area electron diffraction pattern of the junction of Y-junction carbon nanorods.
bon nanorods with various shaped Y-junctions can be used to study
the intrinsic electron transport properties of carbon nanomaterials
and build blocks of nanoelectronics [24].
It is not clear whether this reaction is catalyzed by any of the con-
stituents of the stainless steel cell. To further examine the catalytic
role of the stainless steel wall, a reaction was carried out in a copper
cell under the same experimental conditions. The same products
were obtained. Independent of nanorods formation on the wall
Fig. 4. HRTEM pictures of the product: (a) HRTEM micrograph of a typical carbon
Fig. 5. Nitrogen physisorption results of the carbon nanorods: (a) adsorp-
nanorod and (b) the magnified high-resolution image of the boxed regions in (a).
tion/desorption isotherms and (b) pore size distributions.

Z. Lou et al. / Journal of Alloys and Compounds 507 (2010) 38–41
41
micrometers are produced. As the reaction proceeds, the amount of
carbon bisulfide decreases, and molten metallic lithium falls. Due
to the low mass metal with relatively weak metallic bonds and
under the influence of gravitation of lithium and supercritical CS2,
Li nanodroplet could form forfication on which a Y-junction car-
bon nanorod might grow. Because the number of forfication, the
situation of forfication and the size of a new Li droplet are differ-
ent, they would form various shaped Y-junction carbon nanorods.
These are consistent with our experimental results, of course, due
to the complexity of the experimental process, the exact formation
mechanism of carbon nanorods still needs further research.
4. Conclusions
In summary, carbon nanorods have been successfully synthe-
sized at high yield by reduction of carbon bisulfide with metallic
◦
lithium at 600 C. FESEM, TEM, HRTEM, and N2 isotherm experi-
ments reveal the morphology, size and fine structure of the product.
Many various shaped Y-junction carbon nanorods were also found
to present in the product. It is expected further work could lead
to large-scale preparation of Y-junction carbon nanorods, which
might be significant to the basic building units for nanoelectronic
devices. Because of its simplicity and high yield, this process could
be scaled up for industrial production of carbon nanorods with
novel structure.
◦
Fig. 6. TEM micrograph of the sample produced by the reaction at 600 C for 5 h.
Acknowledgement
materials of the reaction cell makes us rule out the possibility that
metal atoms of the wall catalyzed the formation of nanorods. When
the reaction was conducted at 600 C for 2 h, the main products are
◦
The authors gratefully acknowledge informative discussions
with Professor Qianwang Chen.
graphite and amorphous carbon. When the reaction is carried out at
◦
6
00 C for 5 h, The TEM image (Fig. 6) indicates that a large amount
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