Super capacitors# synthesis# material# analysis#cv#gcd#fra#xrd#ftir#metail oxide#chemical # nano# METLERGY#chemical synthesis# chemical technology#petrolium# renewable energy sources# power storage
Organic Name Reactions for the students and aspirants of Chemistry12th.pptx
SANA (Supercapacitors) final PPT.pptx
1. SYNTHESIS AND CHARACTERIZATION OF
MATERIALS FOR SUPERCAPACITOR
PRESENTED BY:-
SANA PARVEEN
M.TECH [PETROLEUM PROCESSING AND
PETROCHEMICAL ENGINEERING]
Faculty No:-21PKPM102
Enrollment No :-GM6514
Supervised by-
Dr. Mohd. Yusuf Ansari
1
3. INTRODUCTION
ENERGY STORAGE TECHNOLOGIES
Energy storage technologies are essential for
bridging the gap between energy generation and
consumption.
Batteries, supercapacitor, solar cells and emerging
innovations like hydrogen fuel cells are becoming
increasingly important in managing the variability
of renewable sources and ensuring a stable energy
supply.
3
4. ENERGY STORAGE DEVICES
Energy Storage Systems
Electric field
Capacitors
Electro-chemical
Batteries
Fuel Cells
Supercapacitors
Energy Harvestrs
Mechanical
Photovoltic
Thermoelectric
Mechanical
Flywheel
4
5. Function/ Performance Supercapacitor Lithium-ion Battery
Charge time 1–10 seconds 10–60 minutes
Cycle life 1 million or 30,000h 500 and higher
Cell voltage 2.3 to 2.75V 3.6V
Specific energy (Wh/kg) 5 120–240
Specific power (W/kg) Up to 10,000 1000–3000
Cost per kWh $10,000 $250–$1,000 (large system)
Service life (industrial) 10-15 years 5 to 10 years
Charge temperature –40 to 65°C (–40 to 149°F) 0 to 45°C (32°to 113°F)
Discharge temperature –40 to 65°C (–40 to 149°F) –20 to 60°C (–4 to 140°F)
Self-discharge (30 days) High (5-40%) 5% or less
5
Comparative Study Between Supercapacitor, Lithium-ion Battery
6. SUPERCAPACITORS
• Supercapacitors can be defined as an energy storage
device that stores energy electrostatically by polarizing
an electrolytic solution.
• Unlike batteries, no chemical reaction occurs when
energy is being stored or discharged, so ultracapacitors
can go through hundreds & thousands of charging
cycles with no degradation.
• Supercapacitors are also known as double-layer
capacitors or Ultracapacitors.
6
7. Double-layer Capacitors- The energy
storage and release mechanism are based on
nanoscale charge separation at the electrochemical
interface formed between the electrode and
electrolyte. The charge storage mechanism is non-
faradaic and no chemical oxidation-reduction
(redox) reactions are involved.
7
CLASSIFICATION OF SUPER CAPACITOR
8. Pseudocapacitors- The pseudo-capacitors store
electrical energy by electron charge transfer between
electrode and electrolyte (electrons from the electrolyte to
cathode or from cathode to electrolyte). This can be done
by Redox (reduction-oxidation reaction).
8
Hybrid capacitors- capacitors with asymmetric
electrodes one of which exhibits mostly electrostatic and
the other mostly electrochemical capacitance, such as
lithium-ion capacitors.
9. ELECTRODE MATERIALS
Carbon Material [8,9]
I. Activated Carbon(310 F/g)
II. Carbon Nanofiber(188 F/g)
III. Graphene(550 F/g)
Transition Metal Oxide
I. MnO2(1370 F/g)
II. TiO2(2295 F/g)
III. RuO2(1585 F/g)
Conducting Polymer
I. Polypyrrole(PPy) (155 F/g)
II. Polyaniline(PANI) (302.43 F/g)
Latest Electrode Material
I. MOFs (Metal-Organic Frameworks)
Electrochemical
Double Layer (EDLC)
Pseudocapacitor Hybrid
Supercapacitor
• Activated Carbon
• Carbon Nanotubes,
• Carbon Fiber
Metal Oxide.
Conducting
Polymer.
Carbon Material,
Conducting Polymer.
Carbon Material,
Metal Oxide.
9
10. ELECTROLYTE
The Electrolytes determine the supercapacitor’s
characteristics such as [8]
I. Its Operating Voltage,
II. Temperature Range,
III. Equivalent Series Resistance (ESR)
IV. Capacitance. Etc
The most common electrolytes used in
electrochemical supercapacitors are,
I. Aqueous electrolyte
II. Organic electrolyte
Aqueous Electrolytes Organic Electrolytes
• Aqueous electrolytes have
the advantages of high ionic
conductivity, low cost, non-
flammability, non-
corrosiveness, and safety.
• Aqueous electrolytes, on the
other hand, have a much
smaller potential window
(~1.2V) than organic
electrolytes
• KOH, H2SO4 & Na2SO4 are
the most prevalent Aqueous
electrolyte solvents.
• Organic electrolytes may
produce a high working
voltage of up to 4V. The
organic electrolytes have a
high-potential window.
• Acetonitrile (AN) and
propylene carbonate (PC)
are the most prevalent
organic electrolyte solvents.
• Organic electrolytes, have
the following issues:
I. a high resistance restricts
the capacitor's power
density;
II. a high-water content limits
the capacitor's operating
voltage
10
11. RESEARCH GAP
Limited Exploration of Ternary Composites: While binary composite
electrode materials for supercapacitors have received considerable attention,
there is a noticeable scarcity of research focused on ternary composites.
Ternary composites involve the integration of three distinct types of
materials: conducting polymers, metal oxides, and carbon-based materials. Each
of these components has its unique electrochemical properties and synergistic
effects when combined. However, compared to binary composites, the
exploration of ternary combinations is relatively underexplored.
11
12. OBJECTIVE
To synthesize binary and ternary composite material for the supercapacitor’s
electrode.
PI, PPY
PI/CoCu2O4, Ppy/CoCu2O4
PI/CoCu2O4/rGO, Ppy/CoCu2O4/rGO
Characterize the synthesized material through different characterization techniques
like:
Material characterization: XRD, FTIR, SEM.
Electro-chemical characterization: CV, GCD, EIS.
12
13. LITERATURE REVIEW
S.
No.
Electrod
e
Material
s
Method of
Preparati
on
Structura
l and
Morphol
ogical
Characte
risation
Electroc
hemical
Charact
erisatio
n
Electrol
yte
Energy
Density
(WhKg-
1)
Power
Density
(W kg-1)
Specific
Capacitanc
e Fg-1 at
Current
density 1
Ag-1
Ref.
1
PPy film
Modified
Vapour
Phase
Polymeriz
ation
SEM,
TEM,
XRD
CV,
GCD,
EIS
2.0 mol
L−1
KOH
- - 313.6 [1]
2 Polypyrr
ole/graph
ene/sulfu
r
(PPyGS)
Chemical
oxidative
polymeriz
ation
TEM,
XRD,
FTIR
CV,
0.5 M
LiNO3 - - 1440 [2]
13
14. 3
MoS2/Ppy
Oxidative
polymeriz
ed SEM,
TEM
CV,
GCD,
EIS
1 M KCl
solution
- - 182.28 [3]
4 PPy/GO/M
WCNT
Facile
One Step
Potentiost
atic
Technique
SEM,
FTIR,
CV,
GCD,
EIS
1 M
Na2SO4
40.45 441.24 358.69 [4]
5 RGo/PPy/P
ET
Modified
Hummere
s/ In situ
Polymeriz
ation
SEM,
XRD
CV,
GCD,
EIS
1 g of
PVA in 10
ml of DI
water at
11
µWh
cm -2
(6.86
mg cm-
2
0.03
mW cm-
2 6.86
mg cm-2
640
[5]
14
LITERATURE REVIEW
15. 6 Co3O4@
polypyrro
le/MWC
NT
Oxidative
polymerizat
ion
SEM,
TEM,
XRD
CV
6M.KOH 84.58 1500 609 [6]
7 rGO/CoF
e2O4,
using
urea.
rGO/CoF
e2O4/PP
y
Modified
Hummers
method, the
polymerizat
ion method.
SEM,
XRD,
FTIR.
CV,
GCD
EIS
1M
H2SO4
22.8 410 164,
279
[7]
8 CuCo2O
4 NWs-
pPy@CC
E
hydrotherm
al procedure
and
calcination
method.
SEM,
TEM,
XRD,
FTIR
CV
0.1 M
NaOH
- - - [8]
15
16. LITERATURE REVIEW
9 Co3O4@poly
pyrrole/MWC
NT
Oxidative
polymerization
SEM
TEM
XRD
CV
6 M
KOH
84.58 1500 609 [17]
10
ClO4 -doped
PIn films
Electrochemica
l
polymerization
SEM
CV,
GCD
EIS
1.0 M
H2SO4
356.22 700.91 1308.6 [18]
11
MWCNT/S,
MWCNT/S/P
IN
Chemical
oxidative
polymerization
SEM
CV,
GCD
EIS
0.4 M
LiNO3 - - 1043 [19]
12
PIn/RGO
Chemical
oxidative
polymerization
SEM
TEM
CV,
GCD
EIS
1.0 M
H2SO4 36 5000 322.8 [20]
16
17. RAW MATERIALS
Material Purity % State Manufacturers
Indole 99.0 Crystalline Central Druge House P. Ltd.
Pyrrole 97.5 Liquid Central Druge House P. Ltd.
Ferric Chlooride Anhydrous 99 Powder Central Druge House P. Ltd.
Ethanol 99.9 Liquid Lab stream Instruments Pvt. Ltd
H2SO4 98 Liquid Thermo Fisher Scientific Pvt. Ltd.
CuNo3 99.9 Powder Thermo Fisher Scientific Pvt. Ltd.
CoNo3 99.9 Powder Thermo Fisher Scientific Pvt. Ltd.
Oxalic acid 98 Crystalline Thermo Fisher Scientific Pvt. Ltd.
Potassium permanganate
(KMnO4)
97 Crystal Loba chemical Pvt. Ltd.
Hydrochloric acid (HCl) 37 vol./vol Liquid Thermo Fisher Scientific Pvt. Ltd
Sodium hydroxide (NaOH) 99 Pellets Thermo Fisher Scientific Pvt. Ltd
Sodium nitrate (NaNO3) 98 Granular Thermo Fisher Scientific Pvt. Ltd
hydrogen peroxide (H2O2) 30 Wt./vol Liquid Central Druge House P. Ltd.
Natural graphite powder (< 20 microns) Powder CDH Fine Chemical, India.
17
26. CHARACTERIZATION OF MATERIALS
• Material Characterization
1. Scanning electron Microscope (SEM)
2. X-ray diffraction (XRD)
3. Fourier Transform Infrared Spectroscopy (FTIR)
26
27. Scanning Electron Microscopy Analysis
Series of uniformly spaced spheres
with smooth surface to represent the
hierarchical microstructure of
Polyindole.
27
Polyindole
28. PI/CuCo2O4
28
In this SEM picture it appears to
have a dandelion flower-like
structure with aligned Polyindole
nanosheets.
SEM Analysis
29. PI/CuCo2O4/rGO
29
• In PI/CuCo2O4/rGO SEM image,
layer formation and agglomeration
of nanoparticles with each other
(PI/CuCo2O4/rGO) are clearly
visible.
SEM Analysis
30. SEM Analysis
• Cauliflower-like structure conforms
to the formation of polypyrrole
• The tiny grains in these formations
show erratic forms that are very
permeable.
30
Polypyrrole
31. SEM Analysis
In this SEM image of
Ppy/CuCo2O4/rGO, graphene
sheet is clearly visible at (5µm), in
the rearrange (stack) way uniform.
The distribution of CuCo2O4 on
the surface of the polypyrrole and
rGO is also visible.
31
Ppy/CuCo2O4/rGO
32. Ppy/CuCo2O4 SEM image (5µm)
show that each CuCo2O4 have
consistently enlarged diameter
by the PPy coating.
It demonstrates a thin layer of
PPy was developed around each
one in a consistent manner.
32
Ppy/CuCo2O4
SEM Analysis
33. X-Diffraction Analysis
• Primary XRD peaks of PI, Ppy, and
PI/CuCo2O4, Ppy/CuCo2O4,
Ppy/CuCo2O4/rGO, PI/CuCo2O4/rGO
are displayed.
• PI maximum peak intensity is
observed at 2θ⁰=23.68
PI/CuCo2O4/rGO with a d spacing of
3.52 Å.
33
34. • Ppy samples are well indexed at (104),
(111), (220), (311), (400), (511), (440)
and (531) planes and these peaks are
well-matched with (JCPDF Card
no.78-2176) Crystallinity is adjusted
through the polyindole, Ppy without
altering the spinal cubic structure of
CuCo2O4.
• The highest peak is used to determine
the crystalline size of the sample.
34
XRD Analysis
35. Fourier Transform infrared spectroscopy Analysis
• FTIR analysis is used to determine the
functional groups present in the
synthesized samples.
• The significant peak at 3440 cm-1 and
1553 cm-1 shows N-H stretching and
bending.
• The peak at 3405, 1554 and 1498,
1413 cm-1 show C-C stretching and
twisting of the benzoyl ring of indole.
35
36. • The fundamental stretching vibrations of
pyrrole rings are thought to be responsible for
the absorption bands at 849 and 788 cm-1.
• The C-N stretching and C-H deformation
vibrations are connected to the vibration
bands at 1498 and 1054 cm-1, respectively.
36
FTIR Analysis
38. Cyclic Voltammetry Analysis of PI
• Potential Window – (-0.2 to 0.8) V
• Electrolyte – 3M H₂SO₄
• Scan rate – 10,15,20,50,100,200 and
300 mV/s
• Electrode system – Three
38
40. CV Analysis of PI/CuCo2O4/rGO
• Potential Window – (-0.2 to 0.8) V
• Electrolyte – 3M H₂SO₄
• Scan rate – 10,15,20,30,50,100,200
and 300 mV/s
• Electrode system – Three
40
41. CV Analysis of Ppy
• Potential Window – (-0.2 to 0.8) V
• Electrolyte – 3M H₂SO₄
• Scan rate – 10,15,20,30,50,100,200
and 300 mV/s
• Electrode system – Three
41
42. CV Analysis of Ppy/CuCo2O4
• Potential Window – (-0.2 to 0.8) V
• Electrolyte – 3M H₂SO₄
• Scan rate – 10,15,20,30,50,100,200
and 300 mV/s
• Electrode system – Three
42
43. CV Analysis of Ppy/CuCo2O4/rGO
• Potential Window – (-0.2 to 0.8)
V
• Electrolyte – 3M H₂SO₄
• Scan rate – 10,15,20,50,100,200
and 300 mV/s
• Electrode system – Three
43
44. Cyclic Voltammetry Analysis
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Scan rate - mV/s
• Electrode System - Three
44
S.No. Material Specific capacitance
1 PI 260 F/g
2 PI /CuCo2O4 664 F/g
3 PI/CuCo2O4/rGO 995 F/g
4 Ppy 191.92 F/g
5 Ppy /CuCo2O4 361.08F/g
6 Ppy/CuCo2O4/rGO 370.4F/g
45. Specific Capacitance
• As the scan rate increase electrolyte diffusion into
the electrode pore decreases.
• Less diffusion and less interaction between
electrode and electrolyte.
• Hence, less capacitance.
𝐶𝑆𝑃 =
𝐼 𝑉 𝑑𝑣
𝑚𝑣∆𝑉
• In this equation, voltammetric charge ∫ 𝐼 (𝑉)𝑑𝑣 is
obtained by integrating the negative sweeps in the
cyclic voltammograms, v (V/s) denotes the
potential scan rate, V (V) denotes the potential
window, and. m(g) denotes the mass of the active
electrode material.
45
46. Galvanostatic Charge Discharge Analysis of PI
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Current density - 1, 2, 3, 4, 8, 5 A/g
46
47. GCD Analysis of Ppy
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Current density - 1, 2, 3, 4, 5, A/g
47
48. GCD Analysis of PI/CuCo2O4
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Current density - 1, 2, 3, 4, 5, A/g
48
49. GCD Analysis of Ppy/CuCo2O4
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Current density - 1, 2, 3, 4, 5, A/g
49
50. GCD Analysis of PI/CuCo2O4/rGO
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Current density - 1, 2, 3, 4, 5, A/g
50
51. GCD Analysis of Ppy/CuCo2O4/rGO
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Current density - 1, 2, 3, 4, 5, A/g
51
52. GCD Analysis
• Potential Window – (-0.2 to 0.8)V
• Electrolyte – 3M H₂SO₄
• Current density - 1 A/g
52
S.No. Materials Specific
capacitance
1 PI 176 F/g
2 PI/CuCo2O4 564 F/g
3 PI/CuCo2O4/rGO 905 F/g
4 Ppy 156 F/g
5 Ppy/CuCo2O4 360 F/g
6 Ppy/CuCo2O4/rGO 370 F/g
53. Specific Capacitance
• Current density increases
electrochemical reaction increases.
• Hence, Specific capacitance decreases.
• 𝐶𝑆𝑃 =
𝐼∆𝑡
𝑚∆𝑉
• Where Δt (s) denotes the discharge
time,
• voltage range is shown by ΔV (V),
• I (A) is the discharge current, and m (g)
is the mass of the active electrode
material.
53
54. Electrochemical Impedance Spectroscopy Analysis
• Frequency range - 0.1 Hz to 100kHz
• Electrode System – Three
• Nyquist plot characteristics can be described using
an equivalent circuit model containing elements
such as Rs (4.33 solution resistance), Rct (3.70
charge-transfer resistance), CPE (1.04*10-3Ω-s-0.5
constant phase element), W (4.25*10-2Ω-s-0.5),
and T (6.48*10-2 Ω-s-0.5). (Two Warburg
impedance)
54
55. CONCLUSION
• The maximum specific capacitance is 995 F/g, for PI/CuCo2O4/rGO
whereas the specific capacitances Ppy/CuCo2O4/rGO 370, PI/CuCo2O4
664 F/g, Ppy/CuCo2O4 361.08 F/g and pure PI, PPy are 260 and 191 F/g,
respectively.
• When we increased the current density from 1 to 5 A/g, the capacitive
retention of PI/CuCo2O4/rGO nanocomposite reached 92% up to 1000
cycles.
• The morphological alteration of PI, Ppy-based nanocomposites has a
significant influence on their capacitive performance as an electrode
material.
• The PI/CuCo2O4/rGO nanocomposite shows tremendous promise as an
excellent electrode material for supercapacitor applications.
55
56. REFERENCES
1. T. Wang et al., ‘Structural Tuning of a Flexible and Porous Polypyrrole Film by a Template-Assisted Method for Enhanced Capacitance
for Supercapacitor Applications’, ACS Appl Mater Interfaces, vol. 13, no. 15, pp. 17726–17735, Apr. 2021, doi: 10.1021/acsami.1c0355
2. J. John, M. Manoj, A. Abhilash, and S. Jayalekshmi, ‘Sulfur/polypyrrole composite cathodes for applications in high energy density
lithium–sulfur cells’, Journal of Materials Science: Materials in Electronics, vol. 31, no. 16, pp. 13926–13938, Aug. 2020, doi:
10.1007/s10854-020-03952-0.
3. C. C. Tu, P. W. Peng, and L. Y. Lin, ‘Weight ratio effects on morphology and electrocapacitive performance for the MoS 2 /polypyrrole
electrodes’, Appl Surf Sci, vol. 444, pp. 789–799, Jun. 2018, doi: 10.1016/j.apsusc.2018.03.101.
4. M. A. A. Mohd Abdah, N. S. Mohd Razali, P. T. Lim, S. Kulandaivalu, and Y. Sulaiman, ‘One-step potentiostatic electrodeposition of
polypyrrole/graphene oxide/multi-walled carbon nanotubes ternary nanocomposite for supercapacitor’, Mater Chem Phys, vol. 219, pp.
120–128, Nov. 2018, doi: 10.1016/j.matchemphys.2018.08.018
5. M. Barakzehi, M. Montazer, F. Sharif, T. Norby, and A. Chatzitakis, ‘A textile-based wearable supercapacitor using reduced graphene
oxide/polypyrrole composite’, Electrochim Acta, vol. 305, pp. 187–196, May 2019, doi: 10.1016/j.electacta.2019.03.058.
6. C. R. Mariappan et al., ‘Synthesis and electrochemical properties of rGO/polypyrrole/ferrites nanocomposites obtained via a hydrothermal route for
hybrid aqueous supercapacitors’, Journal of Electroanalytical Chemistry, vol. 845, pp. 72–83, Jul. 2019, doi: 10.1016/j.jelechem.2019.05.031
7. S. Ramesh, Y. Haldorai, H. S. Kim, and J. H. Kim, ‘A nanocrystalline Co3O4@polypyrrole/MWCNT hybrid nanocomposite for high
performance electrochemical supercapacitors’, RSC Adv, vol. 7, no. 58, pp. 36833–36843, 2017, doi: 10.1039/c7ra06093
8. Ram B. c. Sarfaraz Ansari,. "Robust electrochemical performance of polypyrrole (PPy) and polyindole (Pin) based hybrid electrode materials for
supercapacitor application: A review", Journal of Energy Storage, 2020
9. Deshmukh Bhakti Bhausaheb and Deshmukh Anjali Bhausaheb, ‘A Review on the Synthesis of CuCo2O4 Based Electrode Material and their
Application in Supercapacitors’, International Journal of Advanced Research in Science, Communication and Technology, pp. 538–542, Mar. 2022,
doi: 10.48175/ijarsct-2925.
56
57. 10.Zhao, C., & Zheng, W. (2015). A review for aqueous electrochemical supercapacitors. Frontiers in Energy Research, 3, 23.
11. Wang, G., Zhang, L., & Zhang, J. (2012). A review of electrode materials for electrochemical supercapacitors. Chemical Society
Reviews, 41(2), 797-828.
12. Moyseowicz, A.; Śliwak, A.; Miniach, E.; Gryglewicz, G., Polypyrrole/iron oxide/reduced graphene oxide ternary composite.
13. Peng, Y.-J.; Wu, T.-H.; Hsu, C.-T.; Li, S.-M.; Chen, M.-G.; Hu, C.-C., Electrochemical characteristics of the reduced graphene
oxide/carbon nanotube/polypyrrole composites for aqueous asymmetric supercapacitors. Journal of Power Sources 2014, 272, 970-978.
14.Zhong, J., et al., Study on Enhancement Mechanism of Conductivity Induced by Graphene Oxide for Polypyrrole Nanocomposites.
Macromolecules, 2015. 48: p. 1592-1597.
15. Zhang, J. and X.S. Zhao, Conducting Polymers Directly Coated on Reduced Graphene Oxide Sheets as High-Performance Supercapacitor
Electrodes. The Journal of Physical Chemistry C, 2012. 116(9): p. 5420-5426.
16. Ramesh, S et al A nanocrystalline Co 3 O 4 @polypyrrole/MWCNT hybrid nanocomposite for high-performance electrochemical
supercapacitors RSC Advances, 2017 7 58 p 36833 36843
17. S. Ramesh, Y. Haldorai, H. S. Kim, and J. H. Kim, ‘A nanocrystalline Co3O4@polypyrrole/MWCNT hybrid nanocomposite for high
performance electrochemical supercapacitors’, RSC Adv, vol. 7, no. 58, pp. 36833–36843, 2017, doi: 10.1039/c7ra06093a.
18. A. Shokry, A. M. Elshaer, J. El Nady, S. Ebrahim, and M. Khalil, ‘High energy density and specific capacity for supercapacitor
based on electrochemical synthesized polyindole’, Electrochim Acta, vol. 423, Aug. 2022, doi: 10.1016/j.electacta.2022.140614.
19. R. Chulliyote, H. Hareendrakrishnakumar, M. Raja, J. M. Gladis, and A. M. Stephan, ‘Enhanced cyclability using a polyindole
modified cathode material for lithium sulphur batteries’, Sustain Energy Fuels, vol. 1, no. 8, pp. 1774–1781, 2017, doi:
10.1039/C7SE00210F.
20. Q. Zhou, D. Zhu, X. Ma, J. Xu, W. Zhou, and F. Zhao, ‘High-performance capacitive behavior of layered reduced graphene oxide
and polyindole nanocomposite materials’, RSC Adv, vol. 6, no. 35, pp. 29840–29847, 2016, doi: 10.1039/C5RA27375G.
57