1

Electronic Supplementary Information

Degradation-induced Capacitance: A New Insight into the Superior

Capacitive Performance of Polyaniline/Graphene Composites

Qin’e Zhang,a An’an Zhou,a Jingjing Wang,a Jifeng Wua and Hua Bai*ab

a College of Materials, Xiamen University, Xiamen, 361005, China, P.R.

b Graphene Industry and Engineering Research Institute, Xiamen University,

361005, China, P. R.

E-mail: baihua@xmu.edu.cn

Electronic Supplementary Material (ESI) for Energy & Environmental Science.This journal is © The Royal Society of Chemistry 2017

2

Calculation of theoretical specific capacitance of PANI/RGO and

HAOANIs

For electroactive polymers and oligomers, the theoretical specific capacitance (CT)

can be predicted by the following equation.1, 2

TnFCEM

Where n is the average number of electrons transferred during the redox reaction, F

is the Faraday constant (= 96485 C mol−1), M is the molecular mass of monomer, is

the potential range. The theoretical capacitance value of ~ 740 F g−1 is obtained2 in the

potential range of −0.2 ~ 0.8 V (or 0 ~ 0.8 V) for PANI. Theoretical gravimetric

capacitance of graphene3, 4 is about 550 F g−1, but the practical specific capacitance4, 5

of RGO is approximately 220 F g−1. If we assume that the surface area of PANI/RGO

composite equals to that of RGO component in the composite, and that the areal specific

capacitance of PANI is the same as that of RGO, the theoretical capacitance of

PANI/graphene composites (PANI content: a), which is about

740 220 1TC a a

Therefore, we can simply calculate the theoretical capacitance of PANI/graphene

composites and hydroxyl or amino terminated oligoanilines (HAOANIs) appearing

below.

a) Flexible graphene/PANI paper (PANI content: 22.3%):6

F g−1740 22.3%+220 77.7% 336TaC

3

b) PANI/RGO composite in this work:

F g−1740 50% 220 50% 480TbC

c) HAOANIs:

F g−11

2 96485 21930.8 110TC

F g−12

2 96485 12060.8 200TC

F g−13

4 96485 16750.8 288TC

d) PANI/RGO composite in this work when HAOANIs are generated.

F g−1220 50% 1207.5 50% 714TdC

4

-0.2 0.0 0.2 0.4 0.6 0.8 1.0-15

-10

-5

0

5

10

15

(C)

-0.2 0.0 0.2 0.4 0.6 0.8 1.0-10

-5

0

5

10

-0.2 0.0 0.2 0.4 0.6 0.8 1.0

-30

-20

-10

0

10

20

30

-0.2 0.0 0.2 0.4 0.6 0.8 1.0-10

-5

0

5

10

Cur

rent

den

sity

(A/g

)

(B) PANI-NMP PANI-NMP+H2O

Cur

rent

den

sity

(A/g

)

PAN-NMP+H2O+ammonia PANI-NMP+dispered graphene

Electro-reduction RGO PANI/RGO by electrodeposition(D)

Potential vs.SCE(V) Potential vs.SCE(V)

Potential vs.SCE(V)

Cur

rent

den

sity

(A/g

)

Potential vs.SCE(V)

Cur

rent

den

sity

(A/g

) Dispered graphene(A)

Fig. S1 (A) The CV curves of dispersed graphene.7 (B) PANI mixed with dispersed

graphene. (C) RGO by electrochemical reduction. (D) PANI/RGO by

electrodeposition.8

5

Table S1 Comparison of position of the new pair of peaks and capacitances based on

graphene-PANI materials

MaterialsPosition of

newpair of peaks

Capacitance Cycle life Ref

Phase–Separated polyaniline/Graphene

CompositeAround

0.4 ~ 0.5V

791 F g−1 at 1.14 A g−1

81.1% after 10000

galvanostatic charge–discharge

cycles

9

RGO/PANI/RGO paper Around0.4 ~ 0.5V

581 F g−1 at 1 A g−1

85% after 10000 galvanostatic

charge–discharge cycles

10

PANI–IL–graphene Around0.4 ~ 0.5V

662 F g−1 at 1.0 A g−1

Less than 7.0% after 5000

charge–discharge cycles at 10 A g−1

11

AT-GO composites Around0.4 ~ 0.5V

769 F g−1 at 1 A g−1

More than 93 to 96% after 2000

cycles

12

3D rGO–PANI Nanofibers

Around0.4 ~ 0.5V

921 F g−1 at 0.45 A g−1

>100% retention at 10 A g−1 for

2000 cycles13

Graphene/PANI composite film

Around0.4 ~ 0.5V

640 F g−1

at 1 A g−1

90% after 1000 charge/discharge

cycles14

PANI@3DGFs composite

Around0.4 ~ 0.5V

596.1 F g−1

at 0.5 A g−1

70.2% capacitance

retention after 5000 cycles

15

6

0 50 100 150 200 250 3000

100

200

300

-0.2 0.0 0.2 0.4 0.6-30

-15

0

15

30

0 20 40

0.0

0.2

0.4

0.6

(C)

Cap

acita

nce

(F/g

)

Cycle number

(A)

Potential vs.SCE(V)

125cycles 150cycles 175cycles 200cycles 300cycles

1cycles 2cycles 25cycles 50cycles 75cycles 100cycles

Cur

rent

den

sity

(A/g

)

(B) 1 cycle 50 cycles 100 cycles 150 cycles 200 cycles 300 cycles

Pote

ntia

l vs.S

CE(

V)

Time/s

Fig. S2 Capacitive performances of PANI. (A) The CV curves of PANI in the potential

ranges from −0.2 ~ 0.6 V at scan rate of 50 mV·s−1 within 300 cycles. (B) The

corresponding GCD curves. (C) Specific capacitance of PANI at different cycle

number.

7

8

Fig. S3 Schematic diagram of the preparation of 3D a-PANI/RGO composite.

9

4000 3000 2000 1000

3D-RGO a-PANI/RGO

Tran

smita

nce/

%

Wavenumbers/cm-1

Fig. S4 FT-IR of 3D RGO and a-PANI/RGO composite.

Compared with the FT-IR spectrum of RGO, the new peaks at 1560cm−1, 1490cm−1,

1398cm−1, and 811 cm−1 were attributed to the vibrations of –C=N, –C=C, –C–N and –

C–H, respectively, which demonstrates the successful combination of PANI with the

RGO hydrogel.16, 17

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Fig. S5 SEM images of a-PANI/RGO composite. Scale bars: (A) 20µm, (B) 10µm

and (C) 5µm. (D) EDX spectrum of a-PANI/RGO composite.

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-0.2 0.0 0.2 0.4 0.6 0.8

-0.008

-0.004

0.000

0.004

0.008

Cur

rent

(mA

)

Potential (V vs. SCE)

10mV/s 25mV/s 50mV/s

Fig. S6 The CV curves of extraction on GCE at different scan rates.

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(A)

-0.2 0.0 0.2 0.4 0.6 0.8-20

-10

0

10

20

30

0 20 40 60 80

0.0

0.2

0.4

0.6

0.8

(C)

-0.2 0.0 0.2 0.4 0.6 0.8-20-15-10

-505

101520

0 20 40 60 80

0.0

0.2

0.4

0.6

0.8

Potential vs.SCE(V)

Cur

rent

den

sity

(A/g

) Composite before extraction Composite after extraction

Cur

rent

den

sity

(A/g

)

Potential vs.SCE(V)

Pote

ntia

l vs.S

CE(

V)

Time/s

Composite before extraction Composite after extraction

(B)

Time/s

Pote

ntia

l vs.S

CE(

V)

3D RGO before extraction 3D RGO after extraction

3D RGO before extraction 3D RGO after extraction

(D)

Fig. S7 The CV (A) and GCD (7.8 A·g−1) (B) curves of as-prepared 3D a-PANI/RGO

composite before and after acetonitrile extraction. The CV (C) and GCD (4.2 A·g−1)

(D) curves of 3D RGO before and after acetonitrile extraction.

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Scheme S1. Degradation of PANI during electrochemical process.

N N N N

NH N N NH

H

NH2 N N NH2

N Nn

N N n

HO OHN N n

N N N NNH2 HO H2NOH

N NO O

-H

NH N N NH N N n

H2O H2O

H2O OH2

The mechanism of the degradation of PANI under acidic conditions is given above.

Compounds containing carbon-nitrogen double bonds can be hydrolyzed to the

corresponding aldehydes or ketones.18, 19 There are plenty of Schiff base structures (Ar-

N=C) in oxidized PANI, thus PANI may hydrolysis catalyzed by acid. As shown in

Scheme S1, water first adds onto the C=N bond, and then the N group leaves. After

deprotonation, C=O bond forms.

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-0.2 0.0 0.2 0.4 0.6 0.8

-60

-30

0

30

60

90

0 300 600 900 1200

0.0

0.2

0.4

0.6

0.8

Cur

rent

den

sity

/ A

g-1

Potential / V vs. SCE

50 mV s-1(A)

Pote

ntia

l / V

vs.

SCE

Time / s

1.19 A g-1(B)

Fig. S8 Electrochemical properties of amino-terminated aniline trimer/PANI

composite. (A) CV curve of composite at scan rate of 50 mV s-1 in the potential range

of − 0.2 ~ 0.7 V. (B) GCD curve of composite at current density of 1.19 A·g−1 under

the potential of 0 ~ 0.7 V.

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-0.2 0.0 0.2 0.4 0.6 0.8

-80

-40

0

40

80

0 200 400 600 800

0.00.10.20.30.40.50.60.7

Curre

nt d

ensit

y (A

/g)

Potential (V vs. SCE)

10mV/s 25mV/s 50mV/s 75mV/s 100mV/s

(A)

Pote

ntia

l (V

vs.

SCE)

Time (s)

1.06A/g 2.12A/g 4.24A/g 8.48A/g 12.72A/g 16.96A/g 21.2A/g 25.44A/g

(B)

Fig. S9 The different scan rates of CV curves (A) and the specific capacitance at

different current density (B).

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-0.2 0.0 0.2 0.4 0.6-10

-5

0

5

10

0 20 40 60 80 100 120

0.0

0.2

0.4

0.6

-0.2 0.0 0.2 0.4 0.6-15

-10

-5

0

5

10

15

0 20 40 60 80 100 120

0.0

0.2

0.4

0.6

0 2 4 6 8 100

20

40

60

80

100

120

0 1000 2000 3000 4000 5000

0

20

40

60

80

100

120

Cur

rent

den

sity

/ A

g-1

Potential / V vs. SCE

Before activation After activation

(A)

Pote

ntia

l / V

vs.

SCE

Time / s

Before activation After activation

(B)C

urre

nt d

ensi

ty /

A g

-1

Potential / V vs. SCE

10 mV s-1

25 mV s-1

50 mV s-1

75 mV s-1

100 mV s-1

(C)

Pote

ntia

l / V

vs.

SCE

Time / s

1.1 A g-1

2.2 A g-1

3.3 A g-1

4.4 A g-1

5.6 A g-1

6.7 A g-1

7.8 A g-1

(D)

Spec

ific

capa

cita

nce

/ F g

-1

Current density / A g-1

(E)

Ret

entio

n ra

te /

%

Cycle number

(F)0 100 200 300 400

0.00

0.05

0.10

0.15

0.20

0.25

Ener

gy d

ensi

ty /

Wh

L1

Current density / A L1

Fig. S10 Capacitive performance of two-electrode devices with PANI/RGO as the

anode (mass loading: 5.1 mg cm−2) and pure RGO as the cathode. (A) CV curves of

device before and after activation of PANI/RGO at 50 mV s−1. (B) GCD curves of

device before and after activation of PANI/RGO at current density of 1.1 A·g−1. (C)

CV curves of device at different scan rate. (D) GCD curves of device at different current

densities. (E) Specific capacitance of device at different current densities. (F)

Capacitance retention of device over 5000 cycles at the current density of 7.8 A·g−1.

The specific capacitance of the device is calculated from GCD curves:

17

cellI tC

m U IR

where I is the constant discharge current, t is the discharging time, m is the total mass

of materials on both electrodes, and U is highest voltage of the cell during

charge/discharge process, and IR is the voltage drop upon discharging.

The energy density is calculated using following equation:

,argdisch eS

I UdtE

V

where V is the total volume of the two electrodes.

18

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