excellent cycle stability nanocomposite as a high ... · calculated using equation s1. energy...
TRANSCRIPT
ESI
Hydrothermally Synthesized BiVO4 –Reduced Graphene Oxide
Nanocomposite as a High Performance Supercapacitor Electrode with
Excellent Cycle Stability
Shibsankar Duttaa, Shreyasi Palb and Sukanta Dea*
aDepartment of Physics, Presidency University, 86/1 College Street, Kolkata-700073, India
bDepartment of Physics, Raidighi College, South 24 Parganas, Diamond Harbour subdivision, Raidighi, West Bengal 743383, India
Corresponding Author: Email: [email protected]
1. Reaction and growth mechanism for BiVO4 nano particle formation
The probable reactions taking place in the BiVO4 formation are shown below
(1)𝐵𝑖(𝑁𝑂3)3.5𝐻2𝑂 + 𝐻𝑁𝑂3 + 𝐻2𝑂 𝐵𝑖𝑂𝑁𝑂3 + 3𝐻𝑁𝑂3
(2)𝐵𝑖𝑂𝑁𝑂3 + 𝑁𝑎3𝑉𝑂4 + 𝐻2𝑂 𝐵𝑖𝑉𝑂4 + 𝑁𝑎𝑁𝑂3 + 𝑁𝑎𝑂𝐻
In the present reaction due to the hydrolysis of , soluble was initially 𝐵𝑖(𝑁𝑂3)3.5𝐻2𝑂 𝐵𝑖𝑂𝑁𝑂3
formed which reacted with the ions provided by at pH ~7 and formed the yellow 𝑉𝑂3 ‒ 𝑁𝑎3𝑉𝑂4
precipitate of tetragonal BiVO4. In the above reaction pH of the solution was controlled by
the NaOH. For the duration of hydrothermal treatment, the formed BiVO4 nuclei was
converted to the well crystalline structure of monoclinic BiVO4 nanocrystals.1 Meanwhile,
the addition of different amount GO into the reaction medium produced the rGO/BiVO4
hybrids.
2. Electrode Preparation:
For electrodes preparation active material, acetylene black and polymer binder (PVDF) in a
ratio of 80:10:10 were mixed with appropriate amount of N-Methyl-2-pyrrolidone to make
slurry. Then the slurry was coated on stainless steel coins and annealed at 180ºC for two
Electronic Supplementary Material (ESI) for New Journal of Chemistry.This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2018
hours in order to remove the binder for the electrodes. Two identical (BiVO4/rGO) electrodes
of mass 2mg with PVA/H2SO4 gel electrolyte were used to construct symmetrical solid state
cell. We have also study the electrochemical performances of the BiVO4/rGO hybrid
electrodes with 1M Na2SO4 solutions as electrolyte using two electrode system. We
systematically study the electrochemical performance of the prepared electrode by two
electrode system using CHI 660E work station.
3. Fabrication of the Solid-State Supercapacitor Device
PVA–H2SO4 gel electrolyte was simply prepared as follows: Initially 3 g H2SO4 was mixed
with 30 mL D.I .water and then 3 g PVA was added to the above mixture under vigorous
stirring at 80°C. The whole mixture was kept at 80°C under continuous stirring until the
solution became clear. Then two electrodes were immersed into the PVA–H2SO4 gel
electrolyte for 5 min. They were then pressed one by one and kept at room temperature for
further measurements.
4. Specific Capacitance Calculation
In the case of two electrodes solid state supercapacitor the specific capacitance value was
calculated using Equation S1. Energy density (E) and power density (P) can also be
calculated from Equation S2 and S3. Where, m was the total mass of the electrode materials,
ΔV (V) is the voltage window, I (A) is the response current, ν (V/s) is the scan rate and Δt
(sec) is the discharge time .2,3
𝐶 =4∫𝐼 𝑑𝑉
𝜈𝑚Δ𝑉 (𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 𝑆1)
𝐸 =18
𝐶(Δ𝑉)2 (𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 𝑆2)
𝑃 =𝐸Δ𝑡
(𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 𝑆3)
5. Supplementary Figures
Fig.S1†: XRD pattern of BiVO4 samples synthesized at different reaction time.
Fig.S2†: XRD pattern of BiVO4/rGO samples with GO concentration variation.
Fig.S3†: XPS survey scan of B-90 sample.
Fig.S4†: CV graphs of all BiVO4 samples using both (a) 1 M Na2SO4 aqueous electrolyte
and (b) PVA/H2SO4 gel electrolyte respectively.
Fig.S5†: CV graphs of the BiVO4/rGO hybrids using both (a) 1 M Na2SO4 aqueous
electrolyte and (b) PVA/H2SO4 gel electrolyte respectively.
Fig.S6†: Electrochemical performance of all the BiVO4 and BiVO4/rGO hybrids electrodes
under investigation.
Fig.S7†: CV graphs of (a) BG2 and (b) B-90 at different scan rates and CD graphs of (c)
BG-2 and (d) B-90 at different current density using 1M Na2SO4 electrolyte.
Fig.S8†: (a) Cycling stability of BG2 for 1000 cycles at a scan rate of 100 mV s−1 using 1M
Na2SO4 electrolyte, (b) FESEM image of BG2 sample after cycle test.
Table S1. Comparison of the electrochemical performance of the BiVO4/rGO supercapacitor
with ternary transition metal oxides and their rGO composites.
Electrode Electrode configura
tion
Electrolyte medium
Specific capacitance
(F/g)
Scan rate
(mV/s)
Current density (A/g)
Energy density (Wh/kg)
Power density
(KW/kg)
Ref.
CoMoO4/graphene
Three 6 KOH 394.5 1 - 54.8 0.197 4
MnFe2O4/graphene
Two (PVA)-H2SO4
120 - 0.1 5.0 0.4 5
NiCo2O4@RGO Three 2 M KOH 737 - 1 - - 6NiCo2O4-CNT Three 6 M KOH 695 - 1 - - 7
CoMoO4/carbon nanotube
Three 1M KOH 170 - 0.1 - - 8
CuCo2O4/Ni foam
Three 6 M KOH 100 - 1 5.98 4.5 9
ZnCo2O4 porousnanotube
Three - 770 - 10 25 2.55 10
ZnCo2O4microspheres
Three - 953.2 - 4 33.1 8 11
MnCo2O4nanostructure
Three - 346 - 1 - - 12
Self-assembledZnCo2O4
nanosheets
Three 2M KOH 1550 - 1 57.4 34.7 13
3D-nanonetCo3O4
Three 6 M KOH 739 F/g - 1 16.42 3 14
MnCo2O4 Three 2 M KOH 290 1 - 10.04 5.2 15
MnWO4 Nanorods
Three NaOH 256.41 - 0.4 - - 16
rGO/BiVO4 Two 151 - 1.4 33.7 8.0 17SWCNT/BiVO4 Three 2 M NaOH 395 2.5 - - 18
Three 1M Na2SO4 563 5 - 200.1 2.88 1M Na2SO4 245 5 - 21.77 0.3
BiVO4/rGO (BG2) Two
PVA/H2SO4 400 5 - 35.37 2.05
Present
work
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