14th International Conference on Optimization of
Electrical and Electronic Equipment OPTIM 2014
May 22-24, 2014, Brasov, Romania
Synthesis, characterization and improvement of α–Co(OH)2 for Supercapacitor
applications
A. Aydın1, Ş. Patat, A. Ülgen, H. Şahan, F. Kılıç Dokan, S. Veziroğlu
1
University of Erciyes, Kayseri, Turkey
Abstract
With the depletion of fossil fuels and the great challenges of the increasing environmental pollution, it is urgent to develop new
materials that provide a high-performance energy storage system combined with low-cost and environmentally friendly
characters. Electrochemical capacitors (ECs), also called supercapacitors or ultracapacitor have attracted growing attention as
important energy storage devices for potential applications in hybrid electric vehicles and mobile electronic devices [1-3]. ECs
store energy using either ion adsorption (electrochemical double-layer capacitors, EDLCs) or fast surface redox reactions
(pseudocapacitors) and they have higher energy density than conventional capacitors and higher power density than batteries.
Pseudocapacitive active materials, such as RuO2.xH2O, have high specific capacitance than those of carbon-based active
materials used in EDLC. However, high-cost and low cell voltage (1 V in aqueous electrolytes) has led to the research interest to
inexpensive electrode materials with good capacitance character without sacrificing the cycle life and power delivery [4-6].
In the present study, α-Co(OH)2 was prepared by a potentiostatic deposition process at −1.0V (vs. Ag/AgCl) onto a
nickel electrode by using a aqueous solution of 0.1 M Co(NO3)2. The structure and surface morphology of the
obtained the α -Co(OH)2 were studied by using X-ray diffraction analysis and scanning electron microscopy.
The capacitive characteristics of the α-Co(OH)2 electrodes were investigated by means of cyclic voltammetry and
constant current charge–discharge cycling in 1 M KOH electrolyte with and without addition of 0.05% Triton X-100.
Galvanostatic charge–discharge curves showed that the capacitance was increased from 720 F g-1 to 804 F g-1 and the
capacitance retention from 63% to 76% after 500 charge/discharge cycles by addition of 0.05% Triton X-100 surface
active materials to 1M KOH electrolyte solution.
Fig. 1 shows the SEM images of the as prepared α-Co(OH)2 electrode, α-Co(OH)2 electrode after first CV and αCo(OH)2 elctrode after 500 charge/discharge cycles. The variation of the specific capacitance and the coulombic
efficiency with the specific current is shown in Fig. 2. Even at the high specific current of 40Ag-1, the specific
capacitance value was 520 Fg-1 for 1.0M KOH aquous solution and 560 Fg-1 for 1.0M KOH aquous solution with
0.05% Triton X-100. The coulombic efficiency () was calculated from thecharge/discharge tests as follow [7]:
 = Qd/Qc × 100 = td /tc × 100
(7)
where tc and td are the times of charging and discharging, respectively. According to the Eq. (7), the average
coulombic effi-ciency was calculated to be about 91.0% for 1.0M KOH aquous solution and 92.5% for for 1.0M
KOH aquous solution with 0.05% Triton X-100 at the high specific current of 40Ag-1. high apecific capacitance and
coulombic efficiency at the high specific current of 40Ag-1 demonstrate the stable reversible characteristics of the
deposited -Co(OH)2.
Fig. 1. SEM images
Fig.2 The specific capacitance and the coulombic efficiency
References
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Kluwer Academic/Plenum, New York, 1999.
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