Supporting information file

Activated graphene as a material for supercapacitor electrodes: effects of surface area, pore size distribution and hydrophilicity.

Artem Iakunkov,a Vasyl Skrypnichuk,a Andreas Nordenström,a Elizaveta A. Shilayev b Mikhail

Korobov,b Mariana Prodana,c Marius Enachescuc, Sylvia H. Larsson,d Alexandr Talyzina*a Department of Physics, Umeå University, Umeå, SE-901 87, Sweden.

b Department of Chemistry, Moscow State University, Leninskie Gory 1-3, Moscow 119991,

Russia

c Center for Surface Science and NanoTechnology, University Politechnica of Bucharest

060042 Bucharest (Romania)

dDepartment of Forest Biomaterials and Technology, Swedish University of Agricultural

Sciences, SE-901 83 Umeå, Sweden

eCIC Energigune, Albert Einstein 48, Alava Technology Park, 01510, Minano, Vitoria-Gasteiz,

Spain

1. Characterization of REF material: XPS , XRD and analysis of nitrogen sorption

isotherms.

2. Data on electrochemical performance of electrodes prepared using REF sample in

supercapacitor cells.

3. Data on electrochemical performance of electrodes prepared using different activation

temperatures

4. Additional data collected using water sorption (DVS method).

5. XPS spectra recorded from samples activated at different temperatures.

6. Gravimetric capacitance and micropore volume.

7. Analysis of nitrogen sorption isotherms for rGO set of samples and electrodes.

8. Electrochemical characterization of the rHGO electrodes.

Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics.This journal is © the Owner Societies 2019

1. Characterization of REF material: XPS , XRD and analysis of nitrogen sorption

isotherms.

300 298 296 294 292 290 288 286 284 282 2800

2000

4000

6000

8000

10000

12000

14000

16000

18000

Inte

nsity

(cps

)

Binding Energy(eV)(a)540 538 536 534 532 530 528 526

0

100

200

300

400

500

600

700

800

(b)

Inte

nsity

(cps

)

Binding Energy(eV)

Figure S1 Part of XPS spectrum recorded from REF-sample (a) C1s and (b) O1s. C/O ratio 31.6%

20 30 40 50 60 70 80

In

tens

ity, a

rb.u

nits

d(100) =2.08Å

Figure S2. XRD pattern of a-rGO (REF sample) and sample free background. Strong diffuse

scattering at low angles is due to disordered structure of porous sample, while presence of in

plane (001) reflection confirms that the sample is composed by defect graphene sheets assembled

in disordered 3D network.

0.0 0.2 0.4 0.6 0.8 1.00

200

400

600

800

1000

1200

1400

1600

1800

BET SA 3030 m2/gVolu

me

(cc/

g)

Relative pressure p/p0

Figure S3 Nitrogen adsorption/desorption isotherm for REF-sample

Figure S4 Pore size distribution calculated using QSDFT equilibrium model for N2 sorption isotherms recorded from set of materials (a) obtained at different activation temperature and (b) after ball milling

(a) (b)

2. Additional information on electrochemical performance of electrodes prepared using REF

sample in supercapacitor cells.

0 1 2 3 4 5

0

2

4

6

8

10

12

-Z'' (

)

Z' ()

0.00 0.25 0.50 0.75 1.00 1.25 1.500.0

0.2

0.4

0.6

0.8

1.0

0.27 kHz

Figure S6 a). Nyquist plot. Electrochemical testing of a-rGO (REF sample) in 6M KOH

electrolyte, standard procedure (see experimental part of main text) for preparation of electrodes.

0.0 0.2 0.4 0.6 0.8 1.0

-15

-10

-5

0

5

10

15

500 mV/s

200 mV/s100 mV/s

50 mV/s

Cur

rent

den

sity

(A g

-1)

Potential (V)0 10 20 30 40 50 60

0.0

0.2

0.4

0.6

0.8

1.0

5A/g 3A/g 2A/g 1A/gC1A/g=106 F/gC2A/g=105 F/gC3A/g=105 F/gC5A/g=105 F/g

Vol

tage

(V)

Time (sec)

0.0 0.2 0.4 0.6 0.8 1.0

-150

-100

-50

0

50

100

150

50 mV/s 100 mV/s 200 mV/s 500 mV/s

Gra

vim

etric

cap

acita

nce

(F g

-1)

Potential (V)0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0

1

2

3

4

-Im

(Z) (

/cm

2 )

ESR = 0.4 cm-2

Re(Z) (/cm2)

Figure S7 Electrochemical testing of a-rGO (MA sample) in 6M KOH electrolyte. a). CV curves

recorded using scan rates 50 mV/s, 100 mV/s, 200 mV/s, 500 mV/s. b) galvanostatic charge-

discharge curves (CDCs) recorded with current density 1 A/g, 2 A/g, 3 A/g, 5 A/g., c) gravimetric

capacitance calculated from CV curves. d) Nyquist plot.

The electrode was prepared using slightly modified procedure using more hydrophilic separator

(Whatman glass separator, thickness of electrode ~100μm, diameter 12mm, mass of one

electrode ~3.3mg ~3.0mg, material/binder ratio – 8/1, pressure ~ 7 tons).

0.0 0.2 0.4 0.6 0.8 1.0

-15

-10

-5

0

5

10

15

C

urre

nt d

ensi

ty (A

g-1)

Potential (V)

50 mV/s

100 mV/s200 mV/s

500 mV/s

0 10 20 30 40 50 600.0

0.2

0.4

0.6

0.8

1.0

5A/g 3A/g 2A/g 1A/gC1A/g=102 F/gC2A/g=102 F/gC3A/g=102 F/gC5A/g=103 F/g

Vol

tage

(V)

Time (sec)

0.0 0.2 0.4 0.6 0.8 1.0

-150

-100

-50

0

50

100

150

200

Gra

vim

etric

cap

acita

nce

(F g

-1)

50 mV/s 100 mV/s 200 mV/s 500 mV/s

Potential (V)0.0 0.5 1.0 1.5 2.0 2.5 3.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Re(Z) (/cm2)

-Im(Z

) (

/cm

2 )ESR = 0.25 cm-2

Figure S8 Electrochemical testing of a-rGO (REF sample) in 6M KOH electrolyte. a). CV curves

recorded using scan rates 50 mV/s, 100 mV/s, 200 mV/s, 500 mV/s. b) galvanostatic charge-

discharge curves (CDCs) recorded with current density 1 A/g, 2 A/g, 3 A/g, 5 A/g., c) gravimetric

capacitance calculated from CV curves. d) Nyquist plot.

Slightly modified procedure was used for preparation of this electrode sample to reduce

electrical resistance by addition of carbon black: whatman glass separator, thickness ~300μm,

diameter 12mm, mass of one electrode ~5.0mg, 81% REF sample, 14% PTEF, 5% Carbon black,

used pressure 2 tons.

Summarizing the data shown in Figures S6-S8, the resistance of electrode can be significantly

reduced using Whatman glass separator and especially strongly by addition of carbon black.

However, the values of gravimetric capacitance (102-105F/g) are not affected by these variations

of preparation procedure.

3. Electrochemical characterization of samples prepared by ball milling for different

periods of time.

0.0 0.2 0.4 0.6 0.8 1.0

-15

-10

-5

0

5

10

Cur

rent

den

sity

(A/g

)

Weight of electrodes 8.7mg

Potential (V)

500 mV/s

200 mV/s100 mV/s

50 mV/s

0 5 10 15 20 25 30 35 40 45 500.0

0.2

0.4

0.6

0.8

1.0

C1A/g=92 F/g

C2A/g=110 F/g

C3A/g=110 F/g

C5A/g=110 F/g

1A/g2A/g3A/g5A/g

Vol

tage

(V)

Time (sec)

Figure S9 Electrochemical characterization of the REF sample after 15 min ball milling (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-15

-10

-5

0

5

10

15

500 mV/s

200 mV/s100 mV/s

50 mV/s

Weight of electrodes 11.8mg

Cur

rent

den

sity

(A/g

)

Potential (V)0 10 20 30 40 50 60

0.0

0.2

0.4

0.6

0.8

1.0

C1A/g=116 F/g

C2A/g=115 F/g

C3A/g=115F/g

C5A/g=118F/g

1A/g2A/g3A/g5A/g

Vol

tage

(V)

Time (sec)

Figure S10 Electrochemical characterization of the REF sample after 30 min ball milling (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-15

-10

-5

0

5

10

15

Weight of electrodes 16.8mg

Cur

rent

den

sity

(A/g

)

50 mV/s

100 mV/s200 mV/s

500 mV/s

0 10 20 30 40 500.0

0.2

0.4

0.6

0.8

1.0

1A/g2A/g3A/g5A/g

Vol

tage

(V)

Time (sec)

C1A/g=97 F/g

C2A/g=97 F/g

C3A/g=97 F/g

C5A/g=100 F/g

Figure S11 Electrochemical characterization of the REF sample after 60 min ball milling (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density. (c) Nyquist plot.

0.0 0.2 0.4 0.6 0.8 1.0

-8

-6

-4

-2

0

2

4

6

8

Weight of electrodes 18.2mg500 mV/s

200 mV/s

100 mV/s

50 mV/s

Cur

rent

den

sity

(A/g

)

Potential (V)0 5 10 15 20 25 30 35 40

0.0

0.2

0.4

0.6

0.8

1.0

Vol

tage

(V)

5A/g 3A/g 2A/g 1A/gC1A/g= 75 F/g

C2A/g=79 F/g

C3A/g=79 F/g

C5A/g=84 F/g

Time (sec)

Figure S12 Electrochemical analysis of the MA sample after 90 min ball milling (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-6

-4

-2

0

2

4

6

500 mV/s

200 mV/s

100 mV/s

50 mV/s

Weight of electrodes 17.1 mgC

urre

nt d

ensi

ty (A

/g)

Potential (V)0 5 10 15 20 25

0.0

0.2

0.4

0.6

0.8

1.0

C1A/g=55 F/g

C2A/g=50 F/g

C3A/g=47 F/g

C5A/g= - F/g

5A/g 3A/g 2A/g 1A/g

Vol

tage

(V)

Time (sec)

Figure S13 Electrochemical characterization of the REF sample after 120 min ball milling (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

3. Additional information on electrochemical performance of electrodes prepared using

different activation temperatures.

0.0 0.2 0.4 0.6 0.8 1.0

-20

-10

0

10

Weight of electrodes 7.2 mg 500 mV/s

200 mV/s100 mV/s

50 mV/s

Cur

rent

den

sity

(A/g

)

Potential (V)(a)0 10 20 30 40 50 60 70

0.0

0.2

0.4

0.6

0.8

1.0

(b)

(a)

V

olta

ge (V

)

5A/g 3A/g 2A/g 1A/gC1A/g= 122 F/g

C2A/g=117 F/g

C3A/g=115 F/g

C5A/g=117 F/g

Time (sec)

Figure S14 Electrochemical characterization of the material obtained at 800°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-20

-10

0

10

Cur

rent

den

sity

(A/g

)

Potential (V)

50 mV/s

100 mV/s200 mV/s

500 mV/sWeight of electrodes 9.3mg

(a)0 10 20 30 40 50 60 70

0.0

0.2

0.4

0.6

0.8

1.0

(b)

(a)

C1A/g=120 F/g

C2A/g=120 F/g

C3A/g=121 F/g

C5A/g=123 F/g

1A/g2A/g3A/g5A/g

Vol

tage

(V)

Time (sec)

Figure S15 Electrochemical characterization of the material obtained at 750°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-15

-10

-5

0

5

10

15

(a)

(a)

C

urre

nt d

ensi

ty (A

/g)

50 mV/s

100 mV/s200 mV/s

500 mV/sWeight of electrodes 10.4mg

Potential (V)0 10 20 30 40 50 60

0.0

0.2

0.4

0.6

0.8

1.0

(b)

(a)

C1A/g=105 F/g

C2A/g=102 F/g

C3A/g=101 F/g

C5A/g=104 F/g

1A/g2A/g3A/g5A/g

Vol

tage

(V)

Time (sec)

Figure S16 Electrochemical characterization of the material obtained at 700°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-15

-10

-5

0

5

10

(a)

(a)

Weight of electrodes 11.2mg 500 mV/s

200 mV/s100 mV/s

50 mV/s

Cur

rent

den

sity

(A/g

)

Potential (V)0 10 20 30 40 50 60

0.0

0.2

0.4

0.6

0.8

1.0

(b)

(a)

C1A/g=105 F/g

C2A/g=100 F/g

C3A/g=102 F/g

C5A/g=110 F/g

1A/g2A/g3A/g5A/g

Vol

tage

(V)

Time (sec)

Figure S17 Electrochemical characterization of the material obtained at 650°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-20

-15

-10

-5

0

5

10

15

(a)

(a)

Potential (V)

Cur

rent

den

sity

(A/g

)

50 mV/s

100 mV/s200 mV/s

500 mV/sWeight of electrodes 11.4mg

0 10 20 30 40 50 60 700.00

0.25

0.50

0.75

1.00

(b)

(a)

V

olta

ge (V

)

Time (sec)

5A/g3A/g 2A/g 1A/gC1A/g=130 F/g

C2A/g=139 F/g

C3A/g=148 F/g

C5A/g=165 F/g

Figure S18 Electrochemical characterization of the material obtained at 600°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-20

-15

-10

-5

0

5

10

15

(a)

(a)

200 mV/s

500 mV/sWeight of electrodes 9.9mgC

urre

nt d

ensi

ty (A

/g)

50 mV/s

100 mV/s

Potential (V)0 10 20 30 40 50 60 70

0.00

0.25

0.50

0.75

1.00

(b)

(a)

V

olta

ge (V

)

5A/g3A/g 2A/g 1A/gC1A/g=110 F/g

C2A/g=132 F/g

C3A/g=131 F/g

C5A/g=150 F/g

Time (sec)

Figure S19 REPEAT Electrochemical characterization of the material obtained at 600°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-20

-15

-10

-5

0

5

10

15

(a)

(a)

Weight of electrodes 8.8mg500 mV/s

200 mV/s100 mV/s

50 mV/s

Cur

rent

den

sity

(A/g

)

Potential (V)0 25 50 75 100

0.00

0.25

0.50

0.75

1.00

(b)

(a)

C1A/g=174 F/g

C2A/g=189 F/g

C3A/g=217 F/g

C5A/g=200 F/g

1A/g2A/g3A/g5A/g

Time (sec)

Vol

tage

(V)

Figure S20 Electrochemical characterization of the material obtained at 550°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-12

-10

-8

-6

-4

-2

0

2

4

6

(a)

(a)

Cur

rent

den

sity

(A/g

)

50 mV/s100 mV/s

200 mV/s500 mV/sWeight of electrodes 9.4mg

0 10 20 30 400.00

0.25

0.50

0.75

1.00

(b)

(a)

Time (sec)

Vol

tage

(V)

C1A/g=162 F/g

C2A/g=189 F/g

C3A/g=195 F/g

C5A/g=193 F/g

5A/g3A/g 2A/g 1A/g

Figure S21REPEAT Electrochemical characterization of the material obtained at 550°C (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

4. Additional data collected using water sorption (DVS method).

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

P/Po

sorption desorption

Onset

mw/m

s, g

g-1

Figure S22 DVS H2O adsorption/desorption isotherm recorded from REF sample.

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

sorption desorption

Onset

mw/m

s , g

g-1

P/P0(a)

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

mw/m

s , g

g-1

P/P0

sorption desorption

(b)

Onset

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

sorption desorption

Onset

mw/m

s , g

g-1

P/P0(c)

Figure S23 DVS H2O adsorption/desorption isotherm recorded from REF sample (a) after 30 min milling, (b) after 60 min milling, (c) after 120 min milling

0.0 0.2 0.4 0.6 0.8 1.00.0

0.1

0.2

sorption desorption

No onset

(a)

mw/m

s , g

g-1

P/P0

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

sorption desorption

No onset

(b)

mw/m

s , g

g-1

P/P0

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

sorption desorption

Onset

(c)

mw/m

s , g

g-1

P/P0

Figure S24 DVS H2O adsorption/desorption isotherm recorded from (a) rGO, (b) GO used as precursor to prepare all a-rGO samples, (c) reference porous carbon sample

5. XPS spectra recorded from samples activated at different temperatures.

300 295 290 285 2800

2000

4000

6000

8000

10000

12000

14000

16000

(a)

Inte

nsity

(cps

)

Binding Energy(eV)542 540 538 536 534 532 530 528

0

100

200

300

400

Inte

nsity

(cps

)

(b)

Binding Energy(eV)

300 297 294 291 288 285 2820

2000

4000

6000

8000

10000

Inte

nsity

(cps

)

Binding Energy(eV)(c)542 540 538 536 534 532 530 528

0

200

400

600

800

1000

1200

(d)

In

tens

ity (c

ps)

Binding Energy(eV)

Figure S25 Part of XPS spectra (a) C1s and (b) O1s recorded from the material obtained at 750°C with C/O ratio 48.2 and (c) C1s and (d) O1s of the material obtained at 550°C with C/O ratio 11.6

6. Gravimetric capacitance and micropore volume.

0.60 0.75 0.90 1.05 1.20

60

80

100

120

140

160

180

Gra

vim

etric

cap

acita

ncce

(A g

-1)

Micropore volume (cc g-1)

550 oC

Figure S26 Correlation of gravimetric capacitance and micropore volume for ■ – set of materials

after milling and ▲ – set of materials obtained at different activation temperature

7. Analysis of nitrogen sorption isotherms for rGO set of samples and electrodes.

0 10 20 30 40 500

50

100

150

200

250

300

350

400

450

500

Por

e vo

lum

e

Cumulative SA Pore Volume

Pore size (Å)

Cum

ulat

ive

SA

BET Surface Area 444 m2/g

slit pore, QSDFT equilibrium model

(a)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0 10 20 30 40 500

50

100

150

200

250

300

350

(b)

(a)

Por

e vo

lum

e

Cumulative SA Pore Volume

Pore size (Å)

Cum

ulat

ive

SA

BET Surface Area 337 m2/g

slit pore, QSDFT equilibrium model

0.00

0.02

0.04

0.06

0.08

0.10

0.12

Figure S27 Pore size distribution and cumulative pore volume calculated using QSDFT equilibrium model for N2 sorption isotherm recorded from (a) rHGO powder and (b) rHGO electrodes.

20 30 40 50 60 70 80 90 1000

100

200

300

400

500

600

700

Cum

ulat

ive

SA

Pore size (Å)

Cumulative SA Pore Volume

BET Surface Area 552 m2/g

slit pore, QSDFT equilibrium model

Por

e vo

lum

e

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0 10 20 30 40 500

50

100

150

200

Cum

ulat

ive

SA

Pore size (Å)

Cumulative SA Pore Volume

BET Surface Area 189 m2/g

slit pore, QSDFT equilibrium model

Por

e vo

lum

e

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0 10 20 30 40 500

10

20

30

40

50

60

Cum

ulat

ive

SA

Pore size (Å)

Cumulative SA Pore Volume

BET Surface Area 69 m2/g

slit pore, QSDFT equilibrium model

Por

e vo

lum

e

0.000

0.002

0.004

0.006

0.008

0.010

0.012

Figure S28 Pore size distribution and cumulative pore volume calculated using QSDFT equilibrium model for N2 sorption isotherm recorded from (a) rBGO powder and (b) rBGO powder after 5 min milling (c) rBGO after 5 min milling electrodes

8. Electrochemical characterization of the rHGO electrodes.

0.0 0.2 0.4 0.6 0.8 1.0

-12

-9

-6

-3

0

3

6

9

C

urre

nt d

ensi

ty (A

/g)

Weight of electrodes 11.5mg 500 mV/s

200 mV/s100 mV/s

50 mV/s

Potential (V)0 10 20 30 40

0.0

0.2

0.4

0.6

0.8

1.0

V

olta

ge (V

)

5A/g3A/g 2A/g 1A/gC1A/g=79 F/g

C2A/g=79 F/g

C3A/g=81 F/g

C5A/g=87 F/g

Time (sec)

Figure S29 Electrochemical characterization of the rHGO electrodes (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-9

-6

-3

0

3

6

9

C

urre

nt d

ensi

ty (A

/g)

Weight of electrodes 15.0mg 500 mV/s

200 mV/s

100 mV/s

50 mV/s

0 10 20 30 400.0

0.2

0.4

0.6

0.8

1.0

C1A/g=62 F/g

C2A/g=67 F/g

C3A/g=68 F/g

C5A/g=72 F/g

1A/g2A/g3A/g5A/g

Vol

tage

(V)

Time (sec)

Figure S30REPEAT. Electrochemical characterization of the rHGO electrodes (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

rBGO has an extremely low bulk density after preparation. To be able to prepare electrodes

it was necessary to apply ball-milling treatment for 5 min to obtain more dense material.

0.0 0.2 0.4 0.6 0.8 1.0

-9

-6

-3

0

3

6

9

C

urre

nt d

ensi

ty (A

/g)

Potential (V)

50 mV/s

100 mV/s200 mV/s

500 mV/sWeight of electrodes 15.9mg

0 5 10 15 20 25 30 35 400.0

0.2

0.4

0.6

0.8

1.0

V

olta

ge (V

)

5A/g3A/g 2A/g 1A/gC1A/g=63 F/g

C2A/g=70 F/g

C3A/g=75 F/g

C5A/g=87 F/g

Time (sec)

Figure S31 Electrochemical characterization of the rBGO electrodes (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.

0.0 0.2 0.4 0.6 0.8 1.0

-6

-3

0

3

6

Potential (V)

50 mV/s

100 mV/s

200 mV/s

500 mV/sWeight of electrodes 20.7mg

Cur

rent

den

sity

(A/g

)

0 5 10 15 20 25 30 350.0

0.2

0.4

0.6

0.8

1.0

V

olta

ge (V

)

Time (sec)

5A/g3A/g 2A/g 1A/gC1A/g=60 F/g

C2A/g=75 F/g

C3A/g=70 F/g

C5A/g=79 F/g

Figure S32 REPEAT Electrochemical characterization of the rBGO electrodes (a) CV analysis at different set of scan rates. (b) Charge/discharge curves recorded at different current density.