Materials Sciences and Applicatio ns, 2011, 2, 1175-1179
doi:10.4236/msa.2011.29158 Published Online September 2011 (http://www.SciRP.org/journal/msa)
1175
Synthesis and Characterization of (Ru-Sn)O2
Nanoparticles for Supercapacitors
Venkata Subba Reddy Channu1*, Rudolf Holze1, Scott Ambrose Wicker Sr.2, Edwin H. Walker Jr.2
Quinton L. Williams3, Rajamohan R. Kalluru3
1Institut für Chemie, AG Elektrochemie, Technische Universität Chemnitz, Chemnitz, Germany; 2Department of Chemistry, South-
ern University and A&M College, Baton Rouge, USA; 3Department of Physics, Atmospheric Sciences and Geoscience, Jackson State
University, Jackson, USA.
Received February 17th, 2011; revised April 26th, 2011; accepted May 31st, 2011.
ABSTRACT
The electrode materials SnO2, RuO2 and (Sn-Ru)O2 were synthesized through precipitation method from SnCl22H2O
and RuCl22H2O solutions. The obtained nano-sized pristine products were characterized using X-ray diffractometry,
Scanning Electron Microscopy (SEM), differential scanning calorimetry (DSC)-thermogravimetric analysis (TGA) and
cyclic voltammetry (CV). The Debye–Scherrer formula was used to estimate the average size of the nanoparticles SnO2
(36 nm), RuO2(24 nm), and (Sn-Ru)O2 (19 nm). Electrochemical studies were carried out to examine the capacitance of
SnO2, RuO2, (Sn-Ru)O2 electrodes in 0.5 M H2SO4 at various scan rates. The estimated electrode capacitance was de-
termined to decrease with an increase of scan rate.
Keywords: Precipitation Synthesis, (Ru-Sn)O2 Nanocomposities, Supercapacitor
1. Introduction
Electrochemical capacitors (ECs) offer greater power
density than well-known batteries and can be quickly
discharged with no deleterious effect on lifetime. They
offer greater energy densities than electrostatic dielectric
capacitors, making them a better option for backup ap-
plications. ECs are becoming attractive energy storage
systems, particularly for applications involving high
power requirements. They are also being studied as a
means to improve battery performance when combined
as a hybrid power source. For instance, hybrid systems
consisting of batteries and electrochemical capacitors are
being pursued for electric vehicle momentum. In such
hybrid systems, ECs can provide the peak power during
acceleration and therefore, the batteries must be opti-
mized primarily for higher energy density and better cy-
cle life.
ECs are also attractive for other applications such as
power sources for lasers, pulsed light generators, digital
single lens reflex (SLR) camera and video flash equip-
ment, backup power sources for computer memory and
as appropriate sources to power quality applications like
Statcons and DVRs [1-3]. Power can be quickly injected
or absorbed to help minimize voltage fluctuations in dis-
tribution systems.
Energy storage mechanisms of electrochemical ca-
pacitors are of two types; first, double-layer capacitance
arising from the charge separation at the electrode/ elec-
trolyte interface and second, pseudocapacitance arising
from fast, reversible faradaic reactions occurring at or
near a solid electrode surface. Carbon materials which
offer high surface area are extensively used for dou-
ble-layer capacitors [4]. On the other hand, transition
metal oxides with relatively high surface area, such as
hydrous RuO2 [5], porous NiOx [6-8], CoOx. [9], and
MnO2 [10-12] have been acknowledged as possible elec-
trode materials for pseudocapacitors.
Tin oxide has been considered as one of the potential
electrode materials for pseudocapacitors. The sol–gel
process, hydrothermal synthesis and sonication methods
have been reported as methods for fabricating porous
SnO2 as an electrode material of ECs [13-16]. These
process methods are highly sophisticated and difficult to
employ in a controlled manner. For instance, the sol–gel
technique is a complicated multi-step process and it is
not easy to precisely control film thickness. The chemical
co-precipitation method is a simple and easy way to pre-

Synthesis and Characterization of (Ru-Sn)O Nanoparticles for Supercapacitors
1176 2
.
pare electroactive materials. Electrode materials for elec-
trochemical capacitors should exhibit high surface area
along with electrochemical activity in the given potential
range and high electric conductivity. The power loss of
ECs is essentially determined by the ohmic IR drop at
high power rate. The conductivity of stoichiometric tin
oxide is very low and pseudo capacitors fabricated by
SnO2 electrodes have low power and energy density.
However, materials mixed with conductive oxides of
transition metals (e.g., RuO2) and characterized by a high
surface area, have a high pseudocapacitive behavior and
a wider potential window of 1V between the anodic and
cathodic solvent discharge [14].
In this work, (Sn-Ru)O2 oxide nanocomposite elec-
trodes were prepared as a candidate for capacitors. A
mixed oxide composition containing 30 wt.% RuO2 was
chosen as it is adequate to modulate the conductive
properties of the system. The effect of the introduction of
RuO2 on the main physiochemical properties was ana-
lyzed.
2. Experimental
The SnCl22H2O powder (28 mM) was dissolved in 100
mL distilled water at room temperature. The pH of the
solution was adjusted to 9 by adding a 3 M NH4OH solu-
tion and stirred for 24 h. The pH-adjusted solution was
placed in an oven at 90˚C for 2 days to obtain dense col-
loid suspension. The obtained colloid suspension was
dried at 60˚C under static-air conditions, for 6 h. The
product was filtered, washed with distilled water, and
dried in air. Calcination was performed at 400˚C for 24 h.
A similar procedure was applied to prepare both RuO2
and (Sn-Ru)O2 nanomaterials.
Crystallographic information of the samples was ob-
tained using an X-ray powder diffractometer (D8 Ad-
vanced Brucker) equipped with graphite monochroma-
tized Cu Kα radiation (λ = 1.54187 Å). Diffraction data
was collected over the 2θ range of 20˚ to 80˚. Micro-
graphs of the nanoproducts were obtained by using a
JEOL Scanning Electron microscope (JSM6390F). For
the TGA measurements, a TA 600 operating in dynamic
mode (heating rate = 10˚C/min), was used. Samples of
5mg weight were placed in an alumina crucible. The
electrochemical properties of the SnO2, (Sn-Ru)O2 and
RuO2 nanoparticles were analyzed by using a
three-electrode cell with a platinum counter electrode and
a silver wire in the 0.1 mol/L AgCl solution as the refer-
ence electrode. The working electrode, prepared by mix-
ing 80 wt% of active material, 15 wt% of acetylene black
and 5 wt% of polytetrafluoroethylene (PTFE), was then
coated on a 1.0 cm2 ITO glass. A 0.5 mol/L solution of
H2SO4 was used as the electrolyte. Cyclic voltammetric
(CV) measurements were carried out between the poten-
tial limits of –0.2 and 1.0 V against Ag/AgCl using a
potentiostat/galvanostat (PRA 273). The CV curves were
recorded at scan rates of 10, 50 and 100 mVs–1
3. Results and Discussion
The phase purity and crystal structure of the samples
have been examined by powder XRD (Figure 1). Sam-
ples are identified as SnO2 and RuO2. The sample pre-
pared from the solution SnCl22H2O was SnO2 and all of
the reflection peaks are indexed to tetragonal SnO2
(JCPDS No: 01-088-0287) with lattice parameters a =
4.73735 Å and c = 3.18640 Å. The diffraction peaks of
the sample prepared from RuCl2.2H2O solution are in-
dexed to the tetragonal RuO2 (JCPDS No: 00-43-1027)
with lattice parameters of a = 4.49940 Å and c = 3.10710
Å. However, in the (Sn-Ru)O2 nanocomposite, peak in-
tensities are decreased and FWHM (broadness) of the
peaks is increased. The broadness of the peaks indicates
either particles of very small crystalline size or particles
which are semicrystalline in nature [15]. Sizes of the
SnO2, RuO2, (Sn-Ru)O2 crystallites were estimated using
the Debye-Scherrer formula to the first peak in the XRD
patterns. The size of SnO2, RuO2 and (Sn-Ru)O2 nano-
particles is 36 nm, 24 nm and 19 nm, respectively.
The thermal data of the SnO2, RuO2 and (Sn-Ru)O2
were measured using the thermogravimetric/differential
scanning calorimeters (TGA/DSC). Typical TGA curves
of the SnO2, RuO2 and (Sn-Ru)O2 measured from room
temperature to 700˚C with heating rate of 10˚C/min are
shown in Figure 2. The total weight loss of SnO2, RuO2
and (Sn-Ru)O2 is 2.7, 3.5 and 4.6 wt%, respectively. The
weight loss of water at temperatures above 300˚C was
due to dehydration of hydroxide groups on the surface of
the oxides. Compared to SnO2 and RuO2, the (Sn-Ru)O2
has more weight loss due to having more water involved
during the formation of composite Sn-Ru oxides.
The SEM observations of the SnO2, RuO2 and
20 30 40 50 60 70 80
(211)
(200)
(101) SnO2 ( JCP DS # 01-088-0287)
(110)
SnO2
2 (degree)
(211)
(200)
(101)
(110)
Intensity (CPS)
RuO2 ( JCPDS # 00-043-1027)
RuO2
70 % SnO 2 + 30 % RuO2
Figure 1. XRD patterns of nanoparticles: SnO2, RuO2 and
(Sn-Ru)O2.

Synthesis and Characterization of (Ru-Sn)O Nanoparticles for Supercapacitors1177
2
0100 200 300 400 500 600 700
95.0
95.5
96.0
96.5
97.0
97.5
98.0
98.5
99.0
99.5
100.0
100.5
SnO2
RuO2
70% S nO 2 + 30% RuO 2
Weight loss (%)
Tem perature( OC)
Figure 2. TGA curves of nanoparticles: SnO2, RuO2 and
(Sn-Ru)O2.
(Sn-Ru)O2 nanomaterials are shown in Figure 3. It is
apparent that the SnO2, RuO2 and (Sn-Ru)O2 nanoparti-
cles are conical and the particles are grown together.
There are several studies available in the literature on
RuO2 complexed as a second component with other ox-
ides [17-22]. The second component RuO2 includes SnO2,
CaO, Carbon, VOx, TiO2, MoO3 [23]. Over the other
complexed oxides, SnO2-RuO2 complex shows higher
electrochemical performance because of higher conduc-
tivity of SnO2.
The capacitance behavior of SnO2, RuO2, (Sn-Ru)O2
nanoparticles in a 0.5M H2SO4 electrolyte with a poten-
tial range of –0.2 V to 1.0 V vs. Ag/AgCl at a scan rate
of 10 mVs–1 is shown in Figure 4. Specific capacitance
of the nanoparticles was calculated from cyclic voltam-
metric (CV) curves using the following equation: C =
i/sm, where i is the average cathodic current, s is the scan
(a) (b)
(c)
Figure 3. SEM photographs of the nanoparticles (a) SnO2,
(b) RuO2 and (c) (Sn-Ru)O2.
-0.20.00.20.40.60.81.0
-4.0x10-3
-3.5x10-3
-3.0x10-3
-2.5x10-3
-2.0x10-3
-1.5x10-3
-1.0x10-3
-5.0x10-4
0.0
5.0x10-4
1.0x10-3
1.5x10-3
2.0x10-3
SnO2
(Sn-Ru )O 2
RuO2
Current[A]
Pot e n tial[ V vs.Ag/ AgCl]
Scanrate:10mV/s
Figure 4. Cyclic voltammograms(CV) of nanoparticles ob-
tained with scan rate 10 mV/s in a 0.5 M H2SO4 as an elec-
trolyte.
rate, and m is the mass of the electrode. The shapes of the
CV curves looks more or less rectangular, and no redox
peaks are observed for SnO2 electrode. From the CV
curve of the (Sn-Ru)O2 composite electrode, a large cur-
rent and symmetrical type of voltammogram with a rec-
tangular shape is found in both anodic and cathodic di-
rections compared to the SnO2 voltammogram. The en-
hancement in electrochemical performance of the com-
posite electrode can be attributed to surface faradic reac-
tions of the doped Ruthenium oxide phase in addition to
the original electrical capacitance of SnO2 electrode.
From the CV curve of the RuO2 electrode, a pair of oxi-
dation and reduction peaks is clearly found on the posi-
tive and negative sweeps at +0.05 V, +0.47 V, +0.41 V
and +0.1 V with high current density compare to the
SnO2, (Sn-Ru)O2 electrodes.
Figures 5-7 shows the cyclic voltammetric(CV) re-
sponses of the SnO2, (Sn-Ru)O2, RuO2 electrodes with
scan rates of 10, 50 and 100 mVs–1. The current under
the curve increased with the increasing scan rate due to
the reaction time is shorter and voltammetric current is
increased if the reversibility is excellent [16]. The meas-
ured specific capacitances were 1.84, 1.63 and 1.46 Fg–1
for SnO2 electrode, 6.08, 4.56 and 3.86 Fg–1 for
(Sn-Ru)O2 electrode, 10.19, 5.79 and 4.65 Fg–1 for RuO2
electrode at scan rates 10, 50, 100 mVs–1, respectively.
The capacitance values decreased with the increase in
scan rate. The observed specific capacitance values are
comparable with reported values of SnO2, (Sn-Ru)O2,
and RuO2 synthesized by other wet chemical methods
[14,24]. Literature reports indicate that the factors af-
fecting the capacitance are particle sizes and electro-
chemical conditions, namely type of electrolyte, concen-
tration of electrolyte, scan rate etc. [14,24]. Some other
factors affecting the capacitance are surface activation

Synthesis and Characterization of (Ru-Sn)O Nanoparticles for Supercapacitors
1178 2
-0.20.0 0.2 0.4 0.6 0.8 1.0
-2.5x10-3
-2.0x10-3
-1.5x10-3
-1.0x10-3
-5.0x10-4
0.0
5.0x10-4
1.0x10-3
1.5x10-3
10mV/s
50mV/s
100mV/s
Current[A]
P ote n tia l[V v s . Ag/AgCl]
SnO2
Figure 5. CV of SnO2 nanoparticles obtained at different
scan rates in a 0.5 M H2SO4 as an electrolyte.
-0.20.00.20.40.60.81.0
-6.0x10-3
-4.0x10-3
-2.0x10-3
0.0
2.0x10-3
4.0x10-3
6.0x10-3
10mV/s
50mV/s
100m V/ s
Current[A]
Potentia l[V vs. Ag/Ag Cl]
(Sn-R u)O2
2
Figure 6. CV of (Sn-Ru)O2 nanoparticles obtained at dif-
ferent scan rates in a 0.5 M H2SO4 as an electrolyte.
-0.20.0 0.20.40.60.81.0
-8.0x10-3
-6.0x10-3
-4.0x10-3
-2.0x10-3
0.0
2.0x10-3
4.0x10-3
6.0x10-3
8.0x10-3
1.0x10-2
10mV/s
50mV/s
100mV/s
Current[A]
Potential[V vs.Ag/AgCl]
RuO2
2
Figure 7. CV of RuO2 nanoparticles obtained at different
scan rates in a 0.5 M H2SO4 as an electrolyte.
under the electrochemical conditions, oxygen content on
the surface, surface oxides and lattice defects resulting
from the method of preparation.
4. Conclusions
The SnO2, RuO2 and (Sn-Ru)O2 nanoparticles were syn-
thesized using a precipitation method. Pristine nanoparti-
cles were characterized using XRD, SEM and TGA
techniques. The average size of the (Sn-Ru)O2 nanopar-
ticles is smaller than that of SnO2 and RuO2 nanoparti-
cles. Compared to SnO2 and RuO2 nanoparticles, the
(Sn-Ru)O2 nanoparticles have more weight loss. An
electrochemical study shows that the RuO2 electrode
exhibits higher capacity than SnO2 and (Sn-Ru)O2 elec-
trodes. The capacitances of the electrodes were found to
decrease with an increase of the scan rate.
5. Acknowledgments
One of the authors (VS Reddy Channu) thank the Alex-
ander von Humboldt Foundation for a fellowship.
REFERENCES
[1] B. E. Conway, “Transition from ‘Supercapacitor’ to
‘Battery’ Behavior in Electrochemical Energy Storage,”
Journal of the Electrochemical Society, Vol. 138, No. 6,
1991, pp. 1539-1548. doi:10.1149/1.2085829
[2] S. Trasatti and P. Kurzweil, “Electrochemical Superca-
pacitors as Versatile Energy Stores,” Platinum Metals
Review, Vol. 38, 1994, pp. 46-56.
[3] S. Sarangapani, B. V. Tilak and C. P. Chen, “Materials
for Electrochemical Capacitors,” Journal of the Electro-
chemical Society, Vol. 143, 1996, pp. 3791-3799.
doi:10.1149/1.1837291
[4] J. M. Miller, B. Dunn, T. D. Tran and R. W. Pekala,
“Deposition of Ruthenium Nanoparticles on Carbon
Aerogels for High Energy Density Supercapacitor Elec-
trodes,” Journal of the Electrochemical Society, Vol. 144,
No. 12, 1997, pp. L309-L311. doi:10.1149/1.1838142
[5] J. P. Zheng, P. J. Cygan and T. R. Zow, “Hydrous Ruthe-
nium Oxide as an Electrode Material for Electrochemical
Capacitors,” Journal of the Electrochemical Society, Vol.
142, 1995, pp. 2699- 2703. doi:10.1149/1.2050077
[6] K. C. Liu and M. A. Anderson, “Porous Nickel Oxide/
Nickel Films for Electrochemical Capacitors,” Journal of
the Electrochemical Society, Vol. 143, No. 1, 1996, pp.
124-130. doi:10.1149/1.1836396
[7] V. Srinivasan and J. W. Weinder, “An Electrochemical
Route for Making Porous Nickel Oxide Electrochemical
Capacitors,” Journal of the Electrochemical Society, Vol.
144, No. 8, 1997, pp. L210-L213. doi:10.1149/1.1837859
[8] V. Srinivasan and J. W. Weinder, “Studies on the Ca-
pacitance of Nickel Oxide Films: Effect of Heating Tem-
perature and Electrolyte Concentration,” Journal of the
Electrochemical Society, Vol. 147, No. 3, 2000, pp. 880-
885. doi:10.1149/1.1393286

Synthesis and Characterization of (Ru-Sn)O2 Nanoparticles for Supercapacitors
1179
[9] C. Lin, J. A. Ritter and B. N. Popov, “Characterization of
Sol-Gel-Derived Cobalt Oxide Xerogels as Electro-
chemical Capacitors,” Journal of the Electrochemical So-
ciety, Vol. 145, No. 12, 1998, pp. 4097-4103.
doi:10.1149/1.1838920
[10] S. C. Pang, M. A. Anderson and T. W. Chapman, “Novel
Electrode Materials for Thin-Film Ultracapacitors: Com-
parison of Electrochemical Properties of Sol-Gel-Derived
and Electrodeposited Manganese Dioxide,” Journal of the
Electrochemical Society, Vol.147, No. 2, 2000, pp. 444-
450. doi:10.1149/1.1393216
[11] S. C. Pang and M. A. Anderson, “Novel Electrode mate-
rials for Electrochemical Capacitors: Part II. Material
Characterization of Sol-Gel-Derived and Electrodeposited
Manganese Dioxide Thin Films,” Journal of Materials
Research, Vol. 15, No. 10, 2000, pp. 2096-2106.
doi:10.1557/JMR.2000.0302
[12] X. U. Jeong and A. Manthiram, “Nanocrystalline Man-
ganese Oxides for Electrochemical Capacitors with Neu-
tral Electrolytes,” Journal of the Electrochemical Society,
Vol. 149, No. 11, 2002, pp. A1419-A1422.
doi:10.1149/1.1511188
[13] N.-L. Wu and S.-Y. Wang, “Preparation of Tin Oxide
Gels with Versatile Pore Structures,” Journal of Materi-
als Science, Vol. 34, No. 12, 1999, pp. 2807-2812.
doi:10.1023/A:1004618915020
[14] C.-C. Hu, K.-H. Chang and C.-C. Wang, “Two-Step
Hydrothermal Synthesis of Ru-Sn Oxide Composites for
Electrochemical Supercapacitors,” Electrochimica Acta,
Vol. 52, No. 3, 2007, pp. 4411-4418.
doi:10.1016/j.electacta.2006.12.022
[15] J. Zhu, Z. Lu, S. T. Aruna, D. Aurbach and A. Gedanken,
“Sonochemical Synthesis of SnO2 Nanoparticles and
Their Preliminary Study as Li Insertion Electrodes,”
Chemistry of Materials, Vol. 12, No. 9, 2000, pp. 2557-
2566. doi:10.1021/cm990683l
[16] R. K. Selvan, I. Perelshtein, N. Perkas and A. Gedanken,
“Synthesis of Hexagonal-Shaped SnO2 Nanocrystals and
SnO2@C Nanocomposites for Electrochemical Redox
Supercapacitors,” The Journal of Physical Chemistry C,
Vol. 112, No. 6, 2008, pp. 1825-1830.
doi:10.1021/jp076995q
[17] C.-C. Hu and K.-H. Chang, “Cyclic Voltammetric Depo-
sition of Hydrous Ruthenium Oxide for Electrochemical
Capacitors: Effects of Codepositing Iridium Oxide,”
Electrochimica Acta, Vol. 45, No. 17, 2000, pp. 2685-
2696. doi:10.1016/S0013-4686(00)00386-8
[18] K.-H. Chang and C.-C. Hu, “Hydrothermal Synthesis of
Binary Ru-Ti Oxides with Excellent Performances for
Supercapacitors,” Electrochimica Acta, Vol. 52, No. 4,
2006, pp. 1749-1757. doi:10.1016/j.electacta.2006.01.076
[19] C.-C. Hu and K.-H. Chang, “Cyclic Voltammetric Depo-
sition of Hydrous Ruthenium Oxide for Electrochemical
Supercapacitors: Effects of the Chloride Precursor Trans-
formation,” Journal of Power Sources, Vol. 112, No. 2,
2002, pp. 401-409. doi:10.1016/S0378-7753(02)00397-X
[20] C.-C. Hu, H.-Yi. Guo, K-H. Chang and C.-C. Huang,
“Anodic Composite Deposition of RuO2·xH2O-TiO2 for
Electrochemical Supercapacitors,” Electrochemistry Com-
munica tions, Vol. 11, No. 8, 2009, pp. 1631-1634.
doi:10.1016/j.elecom.2009.06.014
[21] J. Ribeiro and A. R. De Andrade, “Characterization of
RuO2-Ta2O5 Coated Titanium Electrode,” Journal of the
Electrochemical Society, Vol. 151, No. 10, 2004, pp.
D106-D112. doi:10.1149/1.1787174
[22] C.-C. Hu, Yi-L. Yang and T.-C. Lee, “Microwave-As-
sisted Hydrothermal Synthesis of RuO2·xH2O-TiO2
Nanocomposites for High Power Supercapacitors,” Elec-
trochemical and Solid-State Letters, Vol. 13, No. 12,
2010, pp. A173-A176. doi:10.1149/1.3486437
[23] N.-L. Wu, “Nanocrystalline Oxide Supercapacitors,”
Materials Chemistry and Physics, Vol. 75, No. 1, 2002,
pp. 6-11.
[24] C. C. Hu, C. C. Wang and K. H. Chang, “A Comparison
Study of the Capacitive Behavior for Sol-Gel-Derived
and Co-Annealed Ruthenium-Tin Oxide Composites,”
Electrochimica Acta, Vol. 52, No. 7, 2007, pp. 2691-2700.
doi:10.1016/j.electacta.2006.09.026