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Electronic Supplementary Information (ESI)
Phosphorus and oxygen co-doped composite electrode with
hierarchical electronic and ionic mixed conducting networks
for
vanadium redox flow batteries
Wei Ling,‡a Zhian Wang,‡c Qiang Ma,a Qi Deng,a Jian-Feng Tang,a
Lei Deng,a Liang-Hong Zhu,d Xiong-Wei Wu*a, Jun-Pei Yue*b and
Yu-Guo Guo*b
a.College of Science, Hunan Agricultural University, Changsha,
Hunan 410128, China. E-mail: [email protected] Key
Laboratory of Molecular Nanostructure and Nanotechnology, Institute
of Chemistry, Chinese Academy
of Sciences (CAS), Beijing 100190, China. E-mail:
[email protected].cnc. School of Chemistry and Chemical Engineering,
Central South University, Changsha, Hunan 410083,
China.d.Automotive & Transportation Engineering, Shenzhen
Polytechnic, Shenzhen, Guangdong 518055, China;
‡The authors equally contributed to this work.
ExperimentPreparation of the GF-TCNs electrode The GO solution
was fabricated for standby application according to Hummers’
method.1 Firstly, 1.2 mL phytic acid solution (70 %) was added to
45 mL GO solution (2 mg mL-1) under intensive mixing, and the GFs
(3 cm × 4 cm) were immersed in the aboved solution with 30 min
ultrasonic dispersion. Next, the mixed compounds were sealed in an
80 mL Teflon-lined autoclave and underwent a hydrothermal reaction
at 180 °C for 12 h. After vacuum freeze drying for 24 h, the
resulting products were annealed in a quartz tube furnace under the
argon atmosphere at 800 °C for 1 h. Finally, the obtained GFs and
black solid were washed three times with deionized water and dried
to constant weight at 80 °C for 10 h, and labeled GF-TCNs and TCNs,
respectively.
For comparison purposes, the treated GFs named GF-rGO were
prepared by an identical process as the GF-TCNs without the
addition of phytic acid, and the residual black solid labeled
rGO.Structural characterizationThe morphologies and element
distribution of the electrode materials were characterized from
scanning electron microscope (SEM, JSM-6701F) operated at 10 kV
with energy dispersive spectrometer (EDS). The structural
properties of the electrode materials were analyzed by X-ray
diffraction spectra (XRD, D/max 2500), and Raman spectra (Lab RAM
HR Evolution) with a 532 nm laser excitation. The element
compositions of the samples were determined by X-ray photoelectron
spectroscopy (XPS, ESCALAB250XI) based on a Thermo Scientific
ESCALab 250Xi with 200 W Al Kα radiation. The electrolyte
wettability of electrodes was tested using 100 μL electrolytes (0.1
mol L-1 (M) VOSO4 in 3 M H2SO4) drop on the surface of
electrodes.Electrochemical tests
The cyclic voltammetry (CV) measurements performed on the
electrochemical workstation (CHI760D) were applied to analyze the
electrode reaction process via a three-electrode system2 in the 0.1
M VOSO4 + 3 M H2SO4 electrolyte, and the working electrode area is
0.5 cm× 0.5 cm. The impedance experiments (EIS) are conducted with
a frequency range of 0.01-100 kHz at an amplitude of 5 mV under the
same test condition as CV, and the data were fitted based on
equivalent circuit diagram. The VRFBs assembled pristine GFs and
GF-TCNs electrodes (2 × 2 cm2) were performed for the galvanostatic
charging and discharging tests with Nafion 115 (DuPont, USA) as the
separator, and the electrolyte was 0.75 M VOSO4 + 0.375 M V2(SO4)3
+ 3 M H2SO4 (15 mL) (Hunan Yinfeng Co. Ltd.). The voltage windows
of the dischargeand charge measurements were set as 1.60–0.95 V,
1.65–0.85 V, 1.65-0.80 V and 1.70-0.80 V at current densities range
of 100-150 mA cm-2, 200-225 mA cm-2, 250-300 mA cm-2 and 350 mA
cm-2, respectively.
Electronic Supplementary Material (ESI) for ChemComm.This
journal is © The Royal Society of Chemistry 2019
mailto:[email protected]
-
Figure S1. SEM image and corresponding EDS mappings of the
GF-TCNs with the elements distribution of C, O
and P.
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Figure S2. (a) XPS survey, (b) High-resolution XPS O 1s spectrum
of the GF-rGO.
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Figure S3. The electrolyte wettability of GF, GF-rGO and
GF-TCNs.
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Table S1. The relative element amount of the GF, GF-rGO and
GF-TCNs based on XPS.
% C O N PGF 85.1 12.12 2.78
GF-rGO 84.62 12.26 3.13GF-TCNs 58.71 32.46 2.76 6.06
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Figure S4. (a) The positive and (b) negative CV curves of the
GF-rGO at a scan rate of 10 mV s-1 in the 0.1 M
VOSO4 + 3 M H2SO4 electrolyte
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Table S2. The CV and EIS data of the GF, GF-rGO and GF-TCNs
Positive half-cell Negative half-cell
mA cm-2 V mV mA cm-2 V mV
electrode Ipa Ipc Vpa VpcIpc/
IpaΔE Ipa Ipc Vpa Vpc
Ipc/
IpaΔE
GF 123 88.6 1.21 0.644 0.720 566 18.3 -0.355
GF-rGO 152 128 1.17 0.675 0.842 495 40.6 247 -0.376 -0.743 6.08
367
GF-TCNs 160 140 1.09 0.706 0.875 384 99.4 173 -0.356 -0.667 1.74
311
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Figure S5 Multi-sweep tests of (a) GF, (b) GF-rGO, (c) GF-TCNs
at various rate of 5，8，10，12 and 15 mV/s, (d)
the relationship between the peak current ratio and scan rate of
the GF, GF-rGO and GF-TCNs
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Figure S6. The Nyquist plots of the GF-rGO in the 0.1 M VOSO4 +
3 M H2SO4 electrolyte with the fitting equivalent
circuit based on the Nyquist curve
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Figure S7. (a) Charge-discharge curve, (b) discharge specific
capacity, (c) voltage efficiencye and (d) energy
efficiency of the VRFBs assembled GF-rGO electrodes
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Figure S8. The discharge/charge curves of (a) GF, (b) GF-rGO and
(c) GF-TCNs under various rates
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Figure S9. The cycling performances of the GF-rGO electrode at
200 mA cm−2
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Table S3. The cycle efficiency data of GF, GF-rGO and
GF-TCNs
Current density (mA cm-2)Sample
Efficiency
(%)100 150 200 225 250 300 350
EE 81.7 73.5 66.6 63.0 58.3
GF
VE 83.6 75.1 67.9 64.2 59.1
EE 81.9 74.7 67.8 64.6 60.6
GF-rGO
VE 83.4 76.1 69.2 65.7 61.5
EE 83.0 76.6 70.6 67.6 64.6 58.1 54.0
GF-TCNs
VE 85.5 78.9 72.7 69.6 66.0 59.1 55.1
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Table S4. Comparison of the rate capability and lifespan of the
GF-TCNs electrode with previous work on
electrodes materials for VRFBs
Reference Electrode Cycle
number
Current density
(mA cm-2）
Discharge capacity(Ah L-1)
Energy efficiency
Maximum Current density
(mA cm-2）
This work GF-TCNs 1000100
200
30.0
25.1
83.0
71.0350
3Adv. Funct.
Mater., 2019,
1903192
Exfoilated
-GF100
100
200
21.0
10.0
86.4
60.0200
4J. Mater. Chem. A,
2019, 7, 5589-5600
NiCoO2/G
F50
100
150Not Given
73.7
72.5150
5Nano Energy,
2018, 43, 55-62PGF 500
150
200
28.0
(24.0)
73.0
(68.0)300
6Energy Storage
Mater., 2018, 13,
66-71.
GO-
rGO/GF50
50
100Not Given
87.0
65.0100
7J. Mater. Chem. A,
2018, 6, 6625-
6632.
TiC-GF 6580
10026
67.0
62.0100
8J. Mater. Chem. A,
2018, 6, 41-44.PF-GF 1000
120
200Not Given
79.2
65.0250
9Adv. Energy
Mater., 2017, 7,
1700461
rGO-GF 500150
200
23.0
19.0
75.0
71.0300
10Nano Energy,
2016, 28, 19-28.NCS/GF 350
150
200
27.0
23.0
71.0
67.0300
11ACS Appl. Mater.
Interfaces, 2016, 8,
15369-15378.
ZrO2-GF 200100
200Not Given
78.0
66.0250
12Adv. Sci., 2016, 3,
1500276CF-G-1 100
25
125
20.5 87.0
72.0125
13J. Mater. Chem.
A, 2015, 3, 12276-
12283.
NGF-Co 50100
150
20
(17.5)
80.0
75.0150
14Energy Environ.
Sci., 2014, 7, 3727-
3735.
N-CB-GF 8050
150
19.2
10.1
85.2
70.0150
15Nano Lett., 2014,
14, 158-165Nb-GF 50
50
150
21.5
14.4
75.0
88.0150
-
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