close

Вход

Забыли?

вход по аккаунту

?

j.matchemphys.2018.08.056

код для вставкиСкачать
Accepted Manuscript
Investigation of electrochemical capacitance of 18k nanoporous current collector
incorporated MnO2
V.S. Prabhin, K. Jeyasubramanian, I. Jeyaseeli Rashmi, G.S. Hikku, Pandiyarasan
Veluswamy, Byung Jin Cho
PII:
S0254-0584(18)30721-1
DOI:
10.1016/j.matchemphys.2018.08.056
Reference:
MAC 20899
To appear in:
Materials Chemistry and Physics
Received Date: 29 July 2017
Revised Date:
24 March 2018
Accepted Date: 20 August 2018
Please cite this article as: V.S. Prabhin, K. Jeyasubramanian, I. Jeyaseeli Rashmi, G.S. Hikku, P.
Veluswamy, B.J. Cho, Investigation of electrochemical capacitance of 18k nanoporous current collector
incorporated MnO2, Materials Chemistry and Physics (2018), doi: 10.1016/j.matchemphys.2018.08.056.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Investigation of Electrochemical capacitance of 18k nanoporous current
collector incorporated MnO2
V.S. Prabhina, K. Jeyasubramanianb,*, I. Jeyaseeli Rashmic, G.S. Hikkud, Pandiyarasan
Veluswamye, & Byung Jin Choe
Department of Electronics and Communication, VV College of Engineering,
RI
PT
a
Tisaiyanvilai, India.
*,b
Centre for Nano Science and Technology, Department of Mechanical Engineering,
Mepco Schlenk Engineering College, Sivakasi, India.
Department of Electronics and Communication, Kamaraj College of Engineering and
SC
c
Technology, Virudhunagar, India.
d
Department of Electronics and Communication, PSN College of Engineering and
Department of Electrical Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon
EP
TE
D
34141, Republic of Korea
AC
C
e
M
AN
U
Technology, Tirunelveli, India.
ACCEPTED MANUSCRIPT
Investigation of Electrochemical capacitance of 18k nanoporous current
collector incorporated MnO2
RI
PT
Abstract: This paper deals with the fabrication of super capacitor electrode material employing
a facile etching process followed by electrodeposition. Nanoporous gold current collector has
been fabricated by chemically dealloying commercially available 18k gold having a composition
of 74 % Au and 24 % Cu and 2 % Ag, with dilute HNO3 solution. Electrochemically deposited
SC
MnO2 over the prepared porous Au electrode exhibits a very high specific capacitance value of
1
M
AN
U
670 Fg-1 which is about 1.65 times greater than of MnO2 coated unetched Au electrode (407 Fg). Etched and unetched MnO2 coated electrode materials are characterized using XRD, FESEM
with EDAX and AFM. Electrochemical characterization of the obtained hybrid material is
evaluated by running several cyclic voltagramms using electrochemical workstation. In contrast
to the MnO2 coated unetched Au hybrid electrode system, nanoporous Au-MnO2 electrode
TE
D
displays higher phase angle (79º) and lower time constant (2 ms) derived from the bode plot
suggesting a better capacitance electrode. The high specific capacitances offered with good
charge/discharge rates at a potential window of 0 to 0.8 V, in the scan rate of 100 mV/s for 1000
EP
cycles, exhibiting high-energy storage density of 32.56 wh/kg and 53.6 wh/kg and power density
AC
C
of 366 w/kg and 603 w/kg for un-etched and etched electrodes respectively.
Keywords: Electrochemical deposition, supercapacitor electrode, nanoporous thin gold foil,
etching.
1
ACCEPTED MANUSCRIPT
1. Introduction
Electrochemical supercapacitor is one of the prominent alternative power storing devices
that mainly stores the charges by electrostatic charging (Helmholtz double layer) or reverse
RI
PT
faradic reactions [1]. Recently, it has attracted the attention of researchers since they connect the
energy and power density gap between batteries and capacitors [2]. In the supercapacitor
electrode fabrication, the selection of electrode material and current collector plays a major role.
SC
Current collector is normally chosen from precious metals like gold since it possesses excellent
chemical stability and very high conductivity [3]. Compared to the usage of smooth electrode,
M
AN
U
porous electrodes are widely used in consideration of storage capacity, reaction rates and
transport of mass and charge. The pores found in the electrode not only increase the surface area
but also accommodate more active material that are used and display high specific capacitance
values. Such predominant characteristics of supercapacitor electrode pores are achieved by many
TE
D
routes. Especially, if the pore size is too small (<1 nm), the removal of solvated molecules is
difficult, whereas if the pore size increases beyond the mesoporous range (>50 nm), the
capacitance value gets decreased owing to the reduction in the surface area [4]. So, care should
EP
be taken in controlling the mesoporous range (10-50 nm), otherwise the efficiency might be less.
So far, different kinds of active materials are being used along with electrodes. Selection
AC
C
of these materials is based on some specific characteristics like toxic level, availability, stability,
etc. Among them carbon-based materials like activated carbon, CNT, graphene oxides, graphene,
etc. are most popular, and a few of them have significant porosity and facilitate more charge
storing properties [5-11]. Using hierarchically porous polymer scaffolds and carbon monoliths,
high-voltage aqueous supercapacitors were fabricated which works in the potential window of
2.4V [12]. Composite films produced using graphene-CNT, graphene-polymer combinations and
2
ACCEPTED MANUSCRIPT
edge enriched graphene quantum dots have displayed higher specific capacitances [13, 14].
Doping of metal oxides (CuO2, TiO2) into sulphonated polyaniline (SPAN) enhances the
electrochemical capacitance values [15-19]. The reduced crumbled graphene is used as electrode
RI
PT
material displays higher energy density [20-23]. Conducting polymer-based electrodes are
preferred in medium power applications [24]. While compared with the other electrode materials,
polymer-based materials exhibit reduced lifecycles. Besides, some pervoskite materials are also
SC
used in the fabrication of supercapacitor electrode material [25]. Furthermore, among the
transition metal oxide, MnO2 nanoparticles are used as a dielectric material owing to its high
M
AN
U
capacitance, easy synthesis procedure, availability, nontoxic nature and stability [26-30]. Apart
from the use of nanoporous dielectric materials used in the supercapacitor electrodes, researchers
have developed pores on the electrode by employing various synthetic strategies. Recently, Xing
Lang et al. achieved nanolevel pores on the alloy of Ag65Au35 by dipping into a 70 % HNO3
TE
D
solution [31], and they report about the capacitance of 601Fg-1. Laleh Enayati Ahangar et al
prepared the nanoporous gold electrode from small pieces of recordable compact disk (CD)
made of gold. The protective layer of the CD is etched using nitric acid. Eventually, pores are
[32].
EP
developed on nanometer range which helps in improving the efficiency of the resultant system
AC
C
Instead of using porous Au substrate Jeyasubramanian et al. reported the usage of needle-
shaped Cu collector with fractals having large space that is able to accommodate more charges.
Subsequent coating of nano MnO2 through electrodeposition displays a very high capacitance of
486 Fg-1 [33]. It is clear from all these facts that higher specific capacitance can be achieved by
the usage of nanoporous current collector followed by coating nano-shaped MnO2 particles
through electrodeposition. The novelty of this work is the fabrication of nanoporous Au substrate
3
ACCEPTED MANUSCRIPT
from the commercially available 18k gold foil of thickness around 1.0 mm employing nitric acid
as etchant. Role of porosity generated on the gold substrate is compared with the electrode
surface not having any pores towards the charge storing property of the electrodes. Further, the
RI
PT
electrochemically obtained manganese oxide results in transformation of MnO2 to Mn3O4 and
Mn2O3 which limits the use of this electrode at high temperatures [30]. Since the 18k gold is an
alloy of Au, Cu and Ag, during the etching with nitric acid, the Cu and the Ag atoms present on
SC
the substrate reacts spontaneously with nitric acid and depart from Au foil leaving nanopores.
Electrochemically deposited MnO2 over the porous Au substrate exhibits a very high capacitance
M
AN
U
in contrast to the MnO2 coated unetched Au substrate.
2. Materials and Methods
Sodium sulphate (Na2SO4 ≥ 99% purity), Manganese acetate (Mn(CH3COO)2, 99.9 %
pure, have been purchased from E Merck, India and the thin film of 18 karat gold (74 % gold and
TE
D
24 % Cu and 2 % Ag) substrate with 1mm thickness was purchased from the market, India.
2.1 Synthesis of nanoporous Au substrate
In this study, nanoporous gold electrode is prepared using 18k gold (74 % Au and 26 %
EP
Cu) in the form of thin electrode as electrode material. The gold film is thoroughly cleaned using
acetone and then dipped in 70 % HNO3 for 2 h making the Au electrode porous. On soaking in
AC
C
nitric acid, the copper atom is found on the alloy getting leached into the acid medium leaving a
porous nature. Such a porous structure is one of the prerequisites for electrode material. A facile
method adopted here provides the porosity that can be tuned to any degree depending on the time
in which it is being soaked.
2.2 Electrochemical deposition of MnO2
4
ACCEPTED MANUSCRIPT
The uniform electrodeposition of MnO2 as active material for capacitor application is
employed using Electrochemical workstation (CHI660C, US) in a standard three electrode cell. It
consists of nanoporous gold substrate as a working electrode, Ag/AgCl as a reference electrode
RI
PT
and Pt wire as a counter electrode. Electrochemical deposition of MnO2 have been carried out
with various precursors like manganese acetate, manganese sulphate, manganese nitrate etc., of
which manganese acetate claimed to be a premium source because of its high deposition rate at
SC
lower potentials. The electrochemical reaction of manganese oxide formation from an aqueous
solution of Mn2+ is given below [30],
M
AN
U
Mn2+ + 2H2O → MnO2 + 4H+ + 2e−
The pre-treated porous electrode is dipped in the 100 ml electrolyte bath solution
containing 0.1M (CH3COO)2 Mn.4H2O and 0.1M NaOH with other two electrodes. Under bulk
electrolysis mode and at an operating voltage of 0.5 V, the electrodepositing process was done
TE
D
for 300 sec. After electrodeposition of MnO2 the coated electrode was removed, washed with
water and air dried for 24 h. The quantity of MnO2 deposited on the electrode surface was found
out by weighing equal to 0.0002 g. The same procedure is adopted to coat MnO2 particles over
EP
un-etched Au film too.
3. Results and discussion
AC
C
3.1 XRD analysis of MnO2 deposition
Fig. 1a-b represents the XRD patterns of MnO2 coated over unetched (Fig. 1a) and etched
(Fig. 1b) 18k gold foil using the precursor’s manganese acetate and sodium hydroxide employing
electrochemical deposition technique. From the obtained diffraction peaks, the prepared samples
show tetragonal phase structure with body centered lattice of α-MnO2 (JCPDS No. 72-1982).
The diffraction peaks at 2θ = 38.3°, and 69.3° correspond to the miller indices (121) and (451)
5
ACCEPTED MANUSCRIPT
respectively. The obtained product exhibits single phase crystal with sharp peaks indicating the
crystalline nature of the α-MnO2 [34]. Compared to the unetched substrate, the α-MnO2 coated
over etched substrate shows lesser crystalline nature. This fact may be attributed to the blending
RI
PT
of α-MnO2 into the pores of etched gold foil. However, the less crystalline nature is beneficial to
enhance the electrochemical performance of the fabricated super-capacitor. The amorphous
nature of the oxide layer will provide stress-free insertion and expelling of electrons between the
SC
electrode and the electrolyte. Therefore, the overall performance of the electrode is improved.
Since the α-MnO2 is evenly coated over the 18k gold substrate, the diffraction peaks of Au and
EP
TE
D
M
AN
U
Cu are backed out.
Fig. 1 (a) XRD pattern of MnO2 nanoparticles coated on unetched and (b) etched gold substrate
(c) XPS survey of MnO2 nanoparticles coated over etched Au substrate
AC
C
The chemical composition of MnO2 nanoparticles deposited over Au substrate is
displayed in Fig. 1c. To determine the correct valence of Mn in MnO2, the O 1s spectrum is
evaluated. XPS spectrum also depicts three peaks at 529.7 eV, 531.5 eV and 532.7 eV
contributes anhydrous manganese oxide (Mn-O-Mn), hydrated manganese oxides (Mn-O-H) and
water molecules (H-O-H) respectively [35].
6
ACCEPTED MANUSCRIPT
AC
C
EP
TE
D
M
AN
U
SC
RI
PT
3.2 EDX scan spectra and Elemental mapping
7
ACCEPTED MANUSCRIPT
Fig. 2 EDX-analysis of the electrode (a) un-etched Au substrate (b) un-etched Au substrate after
coating with MnO2 nanoparticles (c) etched Au substrate (d) etched Au substrate after deposition
of MnO2 and (e-h) maps depicting the distribution of O, Mn and Au elements.
RI
PT
The elemental composition of the as-prepared etched electrode was analysed using
elemental Mapping and the results are established in Fig. 2e-h. The Fig. 2f&h reveals that the
elements oxygen and manganese are evenly distributed over the substrate. Fig. 2h depicts the
SC
mapping of etched Au substrate. Here there is no evidence of Cu, however there is some trace
amount of Cu found in EDX spectrum.
M
AN
U
EDX spectrum reveals about the presence of various elements present in the substrate
before and after coating the electro active MnO2 by electrodeposition process. The presence of
the constituent elements found in the electrode is analyzed using Energy dispersive X-ray
spectroscopy. Fig. 2a is the EDX spectrum of 18k gold specimen recorded before etching. Since
TE
D
the commercially available 18k gold is the alloy of Au, Ag and Cu, it shows characteristic peak
for Au as a major peak and Cu as less intense peak. Apart from the two peaks, it also shows
peaks for Ag and Oxygen. Oxygen peak may be originated from the oxide of copper and Ag is
EP
found along with commercial gold. The EDX spectrum of unetched Au substrate after coating
with MnO2 nanoparticles is shown in Fig. 2b. The EDX micro analysis indicates that Mn and O
AC
C
peaks deposited using electrochemical deposition. Fig. 2c is the EDX of Au electrode after
etching with nitric acid. From this it is evident that the less intense peak that has originated from
Cu atom is attributable to its dissolution in acid. However, 100% etching of Cu is not noticed
owing to the thickness of Au foil (1 mm), the complete etching has not taken place. Fig. 2d is the
EDX spectrum of nanoporous Au electrode coated with MnO2 particles. This spectrum revealed
8
ACCEPTED MANUSCRIPT
about the presence of Mn and O peaks originated from MnO2 particles, found apart from Au and
Cu atoms.
EP
TE
D
M
AN
U
SC
RI
PT
3.3 FESEM analysis
Fig. 3 Micrograph of Au specimen (a) before etching, (b) after etching with HNO3, (c) FESEM
AC
C
image of gold/MnO2 hybrid structure on unetched gold substrate, (d) FESEM image of
gold/MnO2 hybrid structure on etched gold substrate
Fig. 3a-d represents the Field Emission Scanning Electron Microscope image recorded
through ZEISS (Germany) at an applied voltage of 20 kV with the magnification of 81000X,
58000X, 50000X and 300000X respectively. Fig. 3a is the FESEM image of the unetched Au
substrate which appears like platelets of Au. Fig. 3b is the FESEM image of the etched gold
substrate obtained after immersing in nitric acid. The image clearly reveals the porous nature of
9
ACCEPTED MANUSCRIPT
substrate having pore size of about 25 nm that arises due to the removal of Cu from 18k Gold.
These facts are more advantageous for supercapacitor electrode material since the porosity
effects of the electrode facilitate the electrochemical faradic transfer rates.
RI
PT
Fig. 3c is the FESEM image of MnO2 coated Au substrate in an unetched electrode. It can
be seen from the figure that it gives the appearance of a needle-shaped MnO2 of size around 15
nm. FESEM image of MnO2 deposited over porous Au electrode is depicted in Fig. 3d. The size
SC
of MnO2 particles is found in the range of 20 nm. Apart from the larger surface area of the
electrode, the higher specific capacitance is also determined by other parameters like pore size
M
AN
U
distribution and the pore shape which influence the transportation of ions in the electrolyte [36].
The image clearly reveals that the nanopores formed after etching by HNO3 are filled with
spherical-shaped MnO2 nanocrystal of size 25 nm.
3.4 Topography studies by AFM
TE
D
AFM images of unetched, etched and MnO2 coated specimens are recorded using XE70
scanning probe microscope, South Korea. Fig. 4a&b represents the AFM image of Au substrate
imaged in such a way that the AFM tip is made to scan the interface of coated and uncoated
EP
regions of MnO2 deposited Au electrode (unetched and etched). The bottom portion of Fig. 4a&b
is the line profile analysis drawn using the software provided by XE70 AFM. The horizontal line
AC
C
drawn across the images ensured about the thickness of MnO2 nanoparticles coated over the Au
substrate. A horizontal line at 0-1.25 µm is drawn that travels in the uncoated region (0-1.25 µm)
and then rises to 50 nm indicating that the thickness of the MnO2 film formed is about 50 nm.
The line profile analysis shown in Fig. 4b corresponds to the Au substrate etched with nitric acid.
The MnO2 particles deposited over it is about 15 nm. It is also measured through the line profile
analysis. In Fig. 4b, at 1.5 µm, the line shoots up to a higher level (0 nm to 1.5 nm) indicating
10
ACCEPTED MANUSCRIPT
almost the thickness of 15 nm of MnO2 coated over porous Au substrate. It is interesting to find
that with the same coating process and time, the thickness of the MnO2 coated over unetched Au
substrate is about 30 nm whereas on the etched Au substrate it is only of 15 nm. This may be due
RI
PT
to the porous nature of the etched current collector used in which the pores of the electrode are
filled by the MnO2 owing to the decrease in the coating thickness to around 15 nm.
Fig. 4d&f is the canny edge image of 3-D AFM image obtained after performing image
SC
processing technique. Edge detection is one of the mathematical method through which it is
possible to identify a digital image where the discontinuity originates or exists. Canny edge
M
AN
U
detector with MATLAB is one of the popular multi-stage edge detection algorithms which is
used to compute sharp gradient and applications seeking edge location of particular objects. The
first and the second gradient derivatives of all pixels found in the image are used to find the
edges of the image and are plotted [37, 38]. Fig. 4f is the canny edge image of Fig. 4e. It clearly
TE
D
displays more gradient peaks located throughout the entire surfaces of coated and uncoated
regions than Fig. 4d which is the canny edge image of Fig. 4c. Fig 4g&h depicts the topography
of unetched and etched Au substrates after the MnO2 is deposited over it. MnO2 particles over
EP
unetched and etched Au substrate are uniformly deposited with a size of 20 nm and 25 nm
respectively. Coating thin MnO2 film in a close proximity to the current collector circumvented
AC
C
the poor conductivity of MnO2 (10-5–10- 6 S cm-1) and reduced solid state transport of insertion
cations [39].
11
AC
C
EP
TE
D
M
AN
U
SC
RI
PT
ACCEPTED MANUSCRIPT
Fig. 4 (a,b) AFM line profile analysis, and (c,e) 3-D top view topography of coated and uncoated
regions of unetched and etched substrate respectively, (d,f) Canny Edge detected image of c and
e, (g,h) AFM topography image of MnO2 coated over unetched and etched substrates
3.5 Electrochemical Analysis
Fig. 5c&d represents the corresponding linear voltage versus time graph for charging and
discharging at the current densities of 0.3 mA, 0.4 mA and 0.5 mA for unetched and etched
12
ACCEPTED MANUSCRIPT
electrodes. The shape of the curve is an equilateral triangle because of the presence of pseudocapacitance characteristics and good reversibility during the charge/discharge processes. It is
clear from the charge-discharge graph that there exists an IR drop or potential drop at the
RI
PT
beginning of the discharging curve. As seen from the charge-discharge profile, it is evident that
the charging and discharge time increases as the current density is decreased. Generally, the IR
drop is resulted from electrolyte resistance, charge transfer resistance of the material and
SC
contact between the electrode and electrolyte [40]. The greater charging and discharging time
for etched Au electrode suggests greater loading of MnO2 in the open pores of the porous
M
AN
U
electrode. A specific capacitance of 360 F/g and 580 F/g is obtained from the galvanostatic
charge discharge curve for unetched and etched Au electrode using the following equation,
=
(1)
∗
where I is the discharge current (mA), and M is the mass of the material coated and the
TE
D
slope taken from charge-discharge curve. Comparison of specific capacitance values obtained
in this work with data available in literature is given in Table 1.
Table 1 Comparison of specific capacitance.
CFF/MnO2
AC
C
Cu/MnO2
Morphology
EP
Electrode material
Capacitance
References
Coral like
-1
467 Fg
[41]
Nano-needles over copper
486 Fg-1
[42]
170 mAg-1
[20]
f-FWNT/r-CGO
Disordered structure
r-GO/r-GONM
Mesh pattern
291/418 Fg-1
[43]
Flat/Nanoporous MnO2
Needle/Porous
407/670 Fg-1
Present work
13
AC
C
EP
TE
D
M
AN
U
SC
RI
PT
ACCEPTED MANUSCRIPT
Fig. 5 (a&b) Cyclic voltammetry (current density vs potential) at various scan rates between 5
mV and 100 mV, (c&d) charge-discharge cycles between 0.5 mA to 0.3 mA, (e) specific
capacitance vs. scan rates, (f) specific capacitance vs. current densities, (g&h) Electrochemical
cycling stability after 1000 cycles in 2 M NaOH electrolyte at a scan rate of 100 mVs-1 for
MnO2 deposited over unetched and etched electrodes respectively
14
ACCEPTED MANUSCRIPT
Fig. 5e outlines the specific capacitance calculated for unetched and etched Au electrodes
for different scan rates. The falling slope in the specific capacitance with the increase in the
=
/
/
/
RI
PT
scan rate is described by Randles - Sevcik equation [44].
(2)
where k is the constant which is equal to 2.72*105, n is the number of moles of electrons
transferred per mole of dielectric species, A is the area of the electrode in cm2, D is the
potential in V/s.
M
AN
U
3.6 Electrochemical Impedance Analysis
SC
diffusion coefficient in cm2 /s, H is the solution concentration in mole/L, and f is the scan
The Nyquist plots for the prepared electrodes at a frequency range of 1 Hz to 100 kHz in
1 M Na2SO4 aqueous solution are shown in Fig. 6a. Fig. 6b represents the magnified portion of
the nyquist plots at higher frequencies in which the full semicircle is not noticed. This may be
TE
D
attributed to the reason that the full semicircle region further falls on the high frequency than 100
kHz which could not be traced by the device. The studies by Shuang Wang et al. [45] discuss
that the highly porous geometrics lead to high frequency semicircle. The Nyquist plots obtained
EP
for etched electrode display a vertical slope with a close ideal capacitive behavior whereas the
unetched electrode does not shows a prominent vertical line which may be due to the leakage
AC
C
problem. Corresponding resistance of 16 Ω and 31 Ω were obtained by extrapolating the vertical
portion of the plot to the real impedance of etched and unetched electrodes, while a transition
time constant semicircle and the ion transport resistance are observed in the regime of 14 Ω and
25 Ω at a frequency of 2.1 kHz and 1 kHz for etched and unetched electrodes respectively.
Fig. 6c&d depicts the equivalent circuit parameters of the unetched and etched Au
electrodes. Here, the resistance R1 is more related to the response of the electrode considering the
geometry of pores and conductivity of the electrode, whereas the resistance R2 is more related to
15
ACCEPTED MANUSCRIPT
the electrolyte property. For a good dynamic capacitor, the difference between R1 and R2 must be
minimum [46]. The difference between R1 and R2 is 3.61 Ω and 1.99 Ω for unetched and etched
Au electrodes respectively. Thus the electrode having pore displays more dynamic character in
AC
C
EP
TE
D
M
AN
U
SC
RI
PT
the typical frequency range.
16
ACCEPTED MANUSCRIPT
Fig. 6 Electrochemical impedance analysis (a) Nyquist plots of unetched and etched sample, (b)
Zoomed Nyquist plot at higher frequencies, (c&d) Equivalent circuit for unetched and etched
electrodes, (e&f) Bode plots for unetched and etched electrodes
RI
PT
In the equivalent circuit shown in the Fig. 6c&d, there is more than one number of series
RC elements in parallel with each other which is possibly the case for overlapping time
constants. The overlapping time constants may originate due to the different charge
SC
accumulation modes such as deep traps, surface roughness, inhomogeneous doping and nonuniform potential distribution [47].
M
AN
U
Fig. 6e&f is the bode plot of the fabricated unetched and etched Au electrodes. The phase
angle and time constant extracted from the bode plots are 55º and 4 ms for unetched Au electrode
and 79º and 2 ms for etched Au electrode. The high phase angle of 80º and low time constant
advocate better supercapacitive phenomenon of the porous electrode [48].
TE
D
The fabricated electrode exhibits good electrochemical performance with an energy
density of 32.56 wh/kg and 53.6 wh/kg and power density of 366 w/kg and 603 w/kg for
=
1
8
=
(3)
(4)
AC
C
EP
unetched and etched electrodes calculated from the following equations [49, 50].
where Cs is the specific capacitance calculated by cyclic voltammetry, V is the voltage
window, and t is the time taken to complete one sweep cycle.
Conclusion
In summary, the hybrid supercapacitor electrode with non-porous and porous Au current
collector is successfully demonstrated. The nano-porous Au substrate developed by chemical
etching process behaves as a double layer capacitor eventually providing good ionic
17
ACCEPTED MANUSCRIPT
conductivity to augment the pseudocapacitive properties of MnO2 crystal. The higher specific
capacitance of 670 Fg-1, high phase angle of 800 and low time constant of 2 ms for etched Au
electrode advocates the good performance of porous electrode. The fabricated electrodes also
RI
PT
fulfill high energy density without sacrificing the power density and cycle stability. This high
performance electrode put forward confidence in the fabrication of supercapacitors using
AC
C
EP
TE
D
M
AN
U
SC
various metal-metal oxides which is needed for high power applications.
18
ACCEPTED MANUSCRIPT
References
AC
C
EP
TE
D
M
AN
U
SC
RI
PT
[1] I.S. Ike, I. Sigalas, S. Iyuke, K.I. Ozoemena, An overview of mathematical modeling of electrochemical
supercapacitors/ultracapacitors, J. Power Sources, 273 (2015) 264-277.
[2] J. Schonberger, Modeling a Supercapacitor using PLECS, Plexim GmbH, version, 4 (2010).
[3] J. Yu, J. Wu, H. Wang, A. Zhou, C. Huang, H. Bai, L. Li, Metallic fabrics as the current collector for highperformance graphene-based flexible solid-State supercapacitor, ACS applied materials & interfaces, 8
(2016) 4724-4729.
[4] P. Simon, Y. Gogotsi, Materials for electrochemical capacitors, Nature materials, 7 (2008) 845-854.
[5] N. Syarif, I.A. Tribidasari, W. Wibowo, Binder-less activated carbon electrode from gelam wood for
use in supercapacitors, Journal of Electrochemical Science and Engineering, 3 (2013) 37-45.
[6] M. Natalia, Y. Sudhakar, M. Selvakumar, Activated carbon derived from natural sources and
electrochemical capacitance of double layer capacitor, (2013).
[7] F. Lufrano, P. Staiti, Mesoporous carbon materials as electrodes for electrochemical supercapacitors,
Int. J. Electrochem. Sci, 5 (2010) 903-916.
[8] T. Chen, L. Dai, Carbon nanomaterials for high-performance supercapacitors, Materials Today, 16
(2013) 272-280.
[9] Q.-L. Chen, K.-H. Xue, W. Shen, F.-F. Tao, S.-Y. Yin, W. Xu, Fabrication and electrochemical properties
of carbon nanotube array electrode for supercapacitors, Electrochimica Acta, 49 (2004) 4157-4161.
[10] M.F. De Volder, S.H. Tawfick, R.H. Baughman, A.J. Hart, Carbon nanotubes: present and future
commercial applications, science, 339 (2013) 535-539.
[11] T. Chen, H. Peng, M. Durstock, L. Dai, High-performance transparent and stretchable all-solid
supercapacitors based on highly aligned carbon nanotube sheets, Scientific reports, 4 (2014) 3612.
[12] G. Hasegawa, K. Kanamori, T. Kiyomura, H. Kurata, T. Abe, K. Nakanishi, Hierarchically porous
carbon monoliths comprising ordered mesoporous nanorod assemblies for high-voltage aqueous
supercapacitors, Chemistry of Materials, 28 (2016) 3944-3950.
[13] K.R. Reddy, B.C. Sin, K.S. Ryu, J. Noh, Y. Lee, In situ self-organization of carbon black–polyaniline
composites from nanospheres to nanorods: synthesis, morphology, structure and electrical conductivity,
Synthetic Metals, 159 (2009) 1934-1939.
[14] M. Hassan, E. Haque, K.R. Reddy, A.I. Minett, J. Chen, V.G. Gomes, Edge-enriched graphene
quantum dots for enhanced photo-luminescence and supercapacitance, Nanoscale, 6 (2014) 1198811994.
[15] K.R. Reddy, B.C. Sin, C.H. Yoo, W. Park, K.S. Ryu, J.-S. Lee, D. Sohn, Y. Lee, A new one-step synthesis
method for coating multi-walled carbon nanotubes with cuprous oxide nanoparticles, Scripta Materialia,
58 (2008) 1010-1013.
[16] M.U. Khan, K.R. Reddy, T. Snguanwongchai, E. Haque, V.G. Gomes, Polymer brush synthesis on
surface modified carbon nanotubes via in situ emulsion polymerization, Colloid and Polymer Science,
294 (2016) 1599-1610.
[17] K.R. Reddy, V.G. Gomes, M. Hassan, Carbon functionalized TiO2 nanofibers for high efficiency
photocatalysis, Materials Research Express, 1 (2014) 015012.
[18] K.R. Reddy, M. Hassan, V.G. Gomes, Hybrid nanostructures based on titanium dioxide for enhanced
photocatalysis, Applied Catalysis A: General, 489 (2015) 1-16.
[19] K.R. Reddy, K.P. Lee, A.I. Gopalan, M.S. Kim, A.M. Showkat, Y.C. Nho, Synthesis of metal (Fe or
Pd)/alloy (Fe–Pd)-nanoparticles-embedded multiwall carbon nanotube/sulfonated polyaniline
composites by γ irradiation, Journal of Polymer Science Part A: Polymer Chemistry, 44 (2006) 3355-3364.
[20] B. Lee, C. Lee, T. Liu, K. Eom, Z. Chen, S. Noda, T.F. Fuller, H.D. Jang, S.W. Lee, Hierarchical networks
of redox-active reduced crumpled graphene oxide and functionalized few-walled carbon nanotubes for
rapid electrochemical energy storage, Nanoscale, 8 (2016) 12330-12338.
19
ACCEPTED MANUSCRIPT
AC
C
EP
TE
D
M
AN
U
SC
RI
PT
[21] S.H. Choi, D.H. Kim, A.V. Raghu, K.R. Reddy, H.-I. Lee, K.S. Yoon, H.M. Jeong, B.K. Kim, Properties of
graphene/waterborne polyurethane nanocomposites cast from colloidal dispersion mixtures, Journal of
Macromolecular Science, Part B, 51 (2012) 197-207.
[22] Y.R. Lee, S.C. Kim, H.-i. Lee, H.M. Jeong, A.V. Raghu, K.R. Reddy, B.K. Kim, Graphite oxides as
effective fire retardants of epoxy resin, Macromolecular Research, 19 (2011) 66-71.
[23] D.R. Son, A.V. Raghu, K.R. Reddy, H.M. Jeong, Compatibility of thermally reduced graphene with
polyesters, Journal of Macromolecular Science, Part B, 55 (2016) 1099-1110.
[24] N. Kurra, R. Wang, H.N. Alshareef, All conducting polymer electrodes for asymmetric solid-state
supercapacitors, Journal of Materials Chemistry A, 3 (2015) 7368-7374.
[25] V.V. Jadhav, M.K. Zate, S. Liu, M. Naushad, R.S. Mane, K. Hui, S.-H. Han, Mixed-phase bismuth
ferrite nanoflake electrodes for supercapacitor application, Applied Nanoscience, 6 (2016) 511-519.
[26] Y. Wang, J. Guo, T. Wang, J. Shao, D. Wang, Y.-W. Yang, Mesoporous transition metal oxides for
supercapacitors, Nanomaterials, 5 (2015) 1667-1689.
[27] T. Gujar, W.-Y. Kim, I. Puspitasari, K.-D. Jung, O.-S. Joo, Electrochemically deposited nanograin
ruthenium oxide as a pseudocapacitive electrode, International Journal of Electrochemical Science, 2
(2007) 666-673.
[28] X. Wang, B.D. Myers, J. Yan, G. Shekhawat, V. Dravid, P.S. Lee, Manganese oxide microsupercapacitors with ultra-high areal capacitance, Nanoscale, 5 (2013) 4119-4122.
[29] S. Ravi, V. Prabhin, High specific capacitance of electrochemically synthesized nano MnO2–gold
electrodes for supercapacitors, Adv. Matt. Lett, 4 (2013) 296.
[30] S. Zhang, G.Z. Chen, Manganese oxide based materials for supercapacitors, Energy Materials, 3
(2008) 186-200.
[31] X. Lang, A. Hirata, T. Fujita, M. Chen, Nanoporous metal/oxide hybrid electrodes for electrochemical
supercapacitors, Nature nanotechnology, 6 (2011) 232.
[32] L.E. Ahangar, M.A. Mehrgardi, Nanoporous gold electrode as a platform for the construction of an
electrochemical DNA hybridization biosensor, Biosensors and Bioelectronics, 38 (2012) 252-257.
[33] K. Jeyasubramanian, T.S.G. Raja, S. Purushothaman, M.V. Kumar, I. Sushmitha, Supercapacitive
performances of MnO 2 nanostructures grown on hierarchical Cu nano leaves via electrodeposition,
Electrochimica Acta, 227 (2017) 401-409.
[34] T. Tao, L. Zhang, H. Jiang, C. Li, Functional carbon nanotube/mesoporous Carbon/MnO 2 hybrid
network for high-performance supercapacitors, Journal of Nanomaterials, 2014 (2014) 1.
[35] N. Yu, H. Yin, W. Zhang, Y. Liu, Z. Tang, M.Q. Zhu, High-Performance Fiber-Shaped All-Solid-State
Asymmetric Supercapacitors Based on Ultrathin MnO2 Nanosheet/Carbon Fiber Cathodes for Wearable
Electronics, Advanced Energy Materials, 6 (2016).
[36] Z. Yu, L. Tetard, L. Zhai, J. Thomas, Supercapacitor electrode materials: nanostructures from 0 to 3
dimensions, Energy & Environmental Science, 8 (2015) 702-730.
[37] S. Agaian, A. Almuntashri, A. Papagiannakis, An improved canny edge detection application for
asphalt concrete, Systems, Man and Cybernetics, 2009. SMC 2009. IEEE International Conference on,
IEEE, 2009, pp. 3683-3687.
[38] R. Biswas, J. Sil, An improved canny edge detection algorithm based on type-2 fuzzy sets, Procedia
Technology, 4 (2012) 820-824.
[39] D. Bélanger, L. Brousse, J.W. Long, Manganese oxides: battery materials make the leap to
electrochemical capacitors, The Electrochemical Society Interface, 17 (2008) 49.
[40] J. Zhang, J. Jiang, H. Li, X. Zhao, A high-performance asymmetric supercapacitor fabricated with
graphene-based electrodes, Energy & Environmental Science, 4 (2011) 4009-4015.
[41] M. Cakici, R.R. Kakarla, F. Alonso-Marroquin, Advanced electrochemical energy storage
supercapacitors based on the flexible carbon fiber fabric-coated with uniform coral-like MnO2
structured electrodes, Chemical Engineering Journal, 309 (2017) 151-158.
20
ACCEPTED MANUSCRIPT
AC
C
EP
TE
D
M
AN
U
SC
RI
PT
[42] K. Jeyasubramanian, T.S.G. Raja, S. Purushothaman, M.V. Kumar, I. Sushmitha, Supercapacitive
performances of MnO2 nanostructures grown on hierarchical Cu nano leaves via electrodeposition,
Electrochimica Acta, 227 (2017) 401-409.
[43] K. Jeyasubramanian, V. Prabhin, G. Hikku, A. Preethi, Investigation of super-capacitive nature of
reduced graphene oxide nano mesh grown over 18 k gold foil using wings of Parides iphidamas as
biological template, Materials Research Bulletin, 98 (2018) 25-33.
[44] A. Inamdar, Y.S. Kim, J.S. Sohn, H. Im, H. Kim, D.-Y. Kim, R. Kalubarme, C. Park, Supercapacitive
characteristics of electrodeposited polyaniline thin films grown on indium doped tin oxide substrates,
Journal of the Korean Physical Society, 59 (2011) 145-149.
[45] S. Wang, B. Hsia, C. Carraro, R. Maboudian, High-performance all solid-state micro-supercapacitor
based on patterned photoresist-derived porous carbon electrodes and an ionogel electrolyte, Journal of
Materials Chemistry A, 2 (2014) 7997-8002.
[46] V. Musolino, L. Piegari, E. Tironi, New full-frequency-range supercapacitor model with easy
identification procedure, IEEE Transactions on Industrial Electronics, 60 (2013) 112-120.
[47] D.K. Kampouris, X. Ji, E.P. Randviir, C.E. Banks, A new approach for the improved interpretation of
capacitance measurements for materials utilised in energy storage, RSC Advances, 5 (2015) 1278212791.
[48] X. Yu, K. Li, H. Zhou, S. Wei, C. Zhang, X. Li, Y. Kuang, Curly graphene nanosheets modified by
nanoneedle-like manganese oxide for electrochemical capacitors, RSC Advances, 5 (2015) 88950-88957.
[49] G.K. Veerasubramani, K. Krishnamoorthy, P. Pazhamalai, S.J. Kim, Enhanced electrochemical
performances of graphene based solid-state flexible cable type supercapacitor using redox mediated
polymer gel electrolyte, Carbon, 105 (2016) 638-648.
[50] K. Krishnamoorthy, G.K. Veerasubramani, S. Radhakrishnan, S.J. Kim, Supercapacitive properties of
hydrothermally synthesized sphere like MoS 2 nanostructures, Materials Research Bulletin, 50 (2014)
499-502.
21
ACCEPTED MANUSCRIPT
Investigation of Electrochemical capacitance of 18k nanoporous current
collector incorporated MnO2
Highlights:
MnO2 is incorporated into porous and flat 18k Au substrates by bulk electrolysis.
RI
PT
The MnO2 depositions are characterized using XRD, XPS, FESEM, EDX mapping
and AFM.
Electrochemical analysis shows the high specific capacitance of the porous electrode.
SC
The impedance analysis suggests the superior characteristics of porous electrode.
AC
C
EP
TE
D
M
AN
U
The prepared electrodes prove to be good candidate for high power applications.
Документ
Категория
Без категории
Просмотров
1
Размер файла
1 601 Кб
Теги
056, 2018, matchemphys
1/--страниц
Пожаловаться на содержимое документа