Synthesis and characterization of hollow spherical copper phosphide (Cu3P) nanopowders

Article abstract of DOI:10.1016/j.ssc.2008.12.046

In this paper, hollow spherical Cu₃P nanopowders were synthesized by using copper sulfate pentahydrate (CuSO₄{dot operator}5H₂O) and yellow phosphorus in a mixed solvent of glycol, ethanol and water at 140-180?^{{ring o}

Full text of DOI:10.1016/j.ssc.2008.12.046

Solid State Communications 149 (2009) 438–440
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Solid State Communications
journal homepage: www.elsevier.com/locate/ssc
Synthesis and characterization of hollow spherical copper phosphide (Cu P)
3
nanopowders
Shuling Liu , Yitai Qianb,c, Liqiang Xu
a
b,∗
a
College of Chemistry and Chemical Engineering, Shaanxi University of Science & Technology, Xi’an 710021, PR China
College of Chemistry and Chemical Engineering, Shandong University, Jinan, 250100, PR China
Department of Chemistry and Structure Research Laboratory, University of Science and Technology of China, Hefei, 230026, PR China
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 April 2007
Received in revised form
In this paper, hollow spherical Cu P nanopowders were synthesized by using copper sulfate pentahydrate
3
◦
(
CuSO4·5H2O) and yellow phosphorus in a mixed solvent of glycol, ethanol and water at 140–180 C for
1
2 h. X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), electron diffraction
2
8 December 2008
pattern (ED) and transmission electronic microscopy (TEM) studies show that the as-synthesized
nanocrystal is pure hexagonal phase Cu3P with a hollow spherical morphology. Based on the TEM
observations, a possible aggregation growth mechanism was proposed for the formation of Cu3P hollow
structures. Meanwhile, the effects of some key factors such as solvents, reaction temperature and reaction
time on the final formation of the Cu3P hollow structure were also discussed.
Accepted 29 December 2008
by C.H.R. Thomsen
Available online 7 January 2009
PACS:
©
2009 Elsevier Ltd. All rights reserved.
6
6
8
1.10.Nz
1.46.Hk
2.20.Yn
Keywords:
A. Nanostructures
B. Crystal growth
E. Crystal structure
1
. Introduction
or quartz ampules [8]. Recently, solvothermal methods [9,10]
have also been reported to prepare Cu3P, but only Cu3P solid
nanoparticles with irregular morphology were obtained.
Copper phosphides have attracted much attention due to their
extant and potential technological properties. When focusing on
the Cu–P system, we find that among all the reported copper
phosphides (Cu3P [1], CuP2, and Cu2P7 [2]), only Cu3P is air stable
and already possesses the industrial applications as a kind of fine
solder and as an important alloying addition [3]. Very recently,
it is reported that Cu3P has good qualities as negative electrode
material in lithium batteries, its gravimetric capacity is close to that
of graphite, but its volumetric capacity is almost four times higher
than that of graphite [4].
2. Experiment
All the chemical reagents were analytical pure grade and
were used without further treatment. In this report, hollow
spherical Cu3P nanopowders were synthesized via a solvothermal
process. In a typical experimental procedure, copper sulfate
pentahydrate (CuSO4·5H2O, 2 mmol) and a mixed solvent (10
mL glycol, 24 mL ethanol and 12 mL water) were mixed with
stirring and were transferred into a Teflon lined autoclave of
Traditionally, Cu3P has been prepared via many routes. For
example, Cu3P was synthesized on an industrial scale by a direct
5
0 mL capacity. When the solution was transparent, yellow
◦
phosphorus (5 mmol) was added. Then, the autoclave was sealed,
solid-state reaction at temperatures higher than 800 C [4],
◦
heated from room temperature to 180 C, and held for 12 h.
electrochemical method by reaction of metal sulfate solution
with phosphorus shines, etc [5–7]. Parkin et al. also reported an
exothermic, self-propagating reaction between sodium phosphide
Subsequently, the autoclave was allowed to cool down to room
temperature naturally. After that, the precipitates were dispersed
in benzene by stirring and the suspension was left for a while to
dissolve unreacted yellow phosphorus; then, they were filtered
and washed successively with absolute ethanol and distilled water
to remove the residual reactants. Finally, the obtained black
(
Na3P) and anhydrous copper halides in evacuated sealed Pyrex
◦
∗
Corresponding author. Tel.: +86 531 8836 4543; fax: +86 531 8836 6280.
E-mail address: xulq@sdu.edu.cn (L. Xu).
sample was dried in vacuum at 50 C for 4 h and collected for
characterization.
0
038-1098/$ – see front matter © 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ssc.2008.12.046

S. Liu et al. / Solid State Communications 149 (2009) 438–440
439
Fig. 2. Typical TEM image, ED pattern (the inset) of the as-prepared Cu3P sample.
P and the solvents (see Eqs. (1) and (2) [11–13]). Once PH3 gases
were generated, copper ions will immediately react with them to
form Cu3P. The produced H3PO3 and H3PO4 undergo successive
reactions shown in Eqs. (3) and (4), which increases the amount of
PH3 and accelerates the reaction of PH3 with the copper ion until
one of the raw materials runs out [14,15].
2
P4 + 12H2O → 3H3PO4 + 5PH3
(1)
(2)
(3)
(4)
P4 + 6C2H5OH → 2H3PO3 + 2PH3 + 6C2H4
4
H3PO3 → PH3 + 3H3PO4
P4 + 6H3PO4 + 6H2O → 10H3PO3
.
In order to investigate the formation process, the TEM images
Fig. 1. Typical XRD pattern (a) and EDX (b) of as-prepared sample prepared at
◦
of the Cu P nanoparticles at different reaction time were obtained.
When the reaction time was prolonged from 3 to 9 h, the
1
80 C for 12 h.
3
amount of solid particles decreased dramatically and the amount
of hollow spheres increased correspondingly (Fig. 3(a)–(c)). When
the reaction time was extended to 10 h, hollow spherical Cu3P
nanoparticles became the majority product (Fig. 3(d)). When the
reaction time was further extended, these hollow spheres were
attached and congregated together and only a dim borderline could
be detected (Fig. 3(e)–(f)).
X-ray powder diffraction (XRD) patterns were carried out on a
Bruker D8 Advanced X-ray diffractmeter with Cu Ka radiation (λ =
1
.5418 Å). The morphologies of the as-prepared samples were
observed by an H-600 transmission electron microscope (TEM)
and a JEM-2100 high-resolution transmission electron microscope
(
HRTEM).
Based on the results of our TEM observations and the hollow
spherical structure of the product, the possible growth process
of these hollow spherical Cu3P nanoparticles is proposed, which
3
. Results and discussion
Fig. 1(a) shows the typical XRD pattern of the as-prepared
◦
is similar to the reported formation processes of Co P hollow
samples at 180 C for 12 h. All the diffraction peaks in this pattern
can be indexed to hexagonal Cu3P phase with lattice constants
a = 6.947 Å, c = 7.066 Å, which are close to those of the reported
values (JCPDS card No. 02-1263). No other peaks that belong to
impurities such as P or Cu could be detected. The purity of the
sample is also determined by EDX (Fig. 1(b)). The result shows
that only Cu and P exist in the product. The fact that Cu3P is only
air stable phosphide among all the copper phosphides [3] further
proves the high purity of the as-obtained sample.
2
tubes and ZnSe microspheres [16,17]. After the initial nucleation,
the newly formed Cu3P nuclei will grow into nanoparticles and
then quickly aggregate into bigger solid particles. Therefore, when
the reaction time was 3 h, only these larger particles were
observed (see Fig. 3(a)). With the increment of the reaction
time, abundant gas bubbles (such as PH3 and C2H4 et al.)
were produced. The smaller nanoparticles might break away
from the initial solid and large aggregated ones under the
circumambience of abundant bubbles, super-saturation and the
pressure of solvothermal conditions, and self-assemble around
the surfaces of these hollow spheres to reduce their surface
energy [18]. Moreover, the dissolution process is temperature
dependent, e.g. it can only take place at high temperatures. A
further temperature-dependent study suggests this point. The
The TEM image of the as-prepared Cu3P sample obtained
◦
at 180 C for 12 h is shown in Fig. 2. It is observed that
the sample consists of a large quantity of nearly spherical
hollow nanoparticles. Their average diameters are in the range
of 200–300 nm. These results reveal that small particles might
aggregate into hollow nanoparticles. The content of these hollow
spherical materials is estimated to be above 90% through the TEM
observations. The three obvious diffraction rings in the ED pattern
◦
product obtained at 140 C for 6–9 h is composed of almost
80% solid spheres. Therefore, we obtain hollow spherical Cu3P
nanoparticles with a high yield when the reaction temperature is
raised or the reaction time is prolonged to a certain reaction stage
(see Fig. 3(e)–(f)). The appearance many small nanoparticles with
a size of 20–30 nm near the aggregated solid and hollow spheres
(
inset in Fig. 2) recorded from the hollow spheres can be indexed as
the (300), (222) and (322) planes of hexagonal Cu3P nanocrystals.
In the present route, the synthesis of Cu3P is based on the
2+
reaction of Cu with PH3. PH3 was produced by the reaction of

4
40
S. Liu et al. / Solid State Communications 149 (2009) 438–440
Fig. 3. Typical TEM images of Cu3P nanocrystals obtained at (a) 3 h, (b) 6 h, (c) 9 h, (d) 10 h, (e) 11 h, (f) 12 h, respectively.
about 90%. The as-obtained hollow spherical nature of the Cu3P
nanoparticles with other species or surface modification might
present an interest in potential technological properties such as
alternative devices as anode materials for lithium ion batteries,
where special issues are required [4].
Acknowledgements
We thank the financial support from the Scientific Research
Foundation for Doctoral Program of Shaanxi University of Science
&
Technology (BJ07-04), the Scientific Research Planning Program
of the Education Department of Shaanxi Province (08JK225), the
National Natural Science Funds (20671058) and the 973 Projects
of China (2005CB623601).
Fig. 4. The magnified TEM images of some small nanoparticles (as arrowed) near
the solid and hollow spheres prepared at (a) 6 h, (b) 9 h.
(
as arrowed in Fig. 4(a) and Fig. 4(b)) during the reactions might
further prove the above process. However, due to the relative
complex and fast velocities of the reaction system involved in
this experiment, the exact formation mechanism of the hollow
spherical Cu3P nanoparticles still needs further research.
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In conclusion, we report a simple and mild solvothermal route
[
to synthesize Cu3P hollow spherical nanoparticles with a yield of