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Supporting Information Controlled Growth of Whisker-like Polyaniline on Carbon Nanofibers and Their Long Cycle Life for Supercapacitor Junyi Wei, Jianan Zhang, Yang Liu, Guiheng Xu, Zhimin Chen, and Qun Xu*

Electrochemical measurement by three-electrode system in 1 M H2SO4

The capacitance performances of the samples were also evaluated in three-electrode system

for reference. The preparation of thin film electrode is similar to that described in the

experimental section. A slurry of PANI/CFs was prepared by thoroughly mixing PANI/CFs,

carbon black and poly(tetrafluoroethylene) (60% in dispersion in H2O) in a mass ratio of

80:10:10. The slurry was then pasted onto stainless steel (0.7×0.7 cm2) to form the tested

electrode and then dried at 60 ℃ for 24h. The prepared electrode, Ag/AgCl electrode and

platinum wire were connected to a CHI 660D workstation (CH Instrument, Inc.) and served as

working, reference and counter electrodes, respectively. The electrochemical measurements

were carried out in 1 M H2SO4.

The CV curves of PANI/CFs with different initial ANI concentration: 5, 10, 25, and 50 mM

are presented in Figure S1a. Each CV curve presents two pairs of redox peaks (O1/R1 and

O2/R2) implying the pseudocapacitance characteristic and the reversible charge-discharge

behaviors. The current density response of PANI/CFs evidently increases with the ANI

concentration, indicating a growth of specific capacitance of PANI/CFs with increase of the

ANI concentration.

Figure S1b shows the specific capacitance of PANI/CFs with different ANI concentration at

different scan rate 5, 10, 20, 50, and 100 mV/s. The specific capacitances were calculated

according to Equation 1(See the main text). The specific capacitances of PANI/CFs with 5

mM ANI remained steady from 245, 238, and 229 to 213 F g-1 and had a reduction to 185 F

g-1 with the increase of scan rate. The specific capacitances of PANI/CFs with 10 mM ANI are

in the same trend, decreasing from 273, 263, 250, and 216 to 134 F g-1. The leveling out of

specific capacitance with the increase of scan rate indicates that the electrochemical stability

of PANI/CFs with 5 and 10 mM. The specific capacitance of PANI/CFs with 25 mM declined

from 581, 554, and 507 F g-1 to 301 and slump down to139 F g-1. The specific capacitance of

PANI/CFs with 50 mM ANI is very close to that with 25 mM, in agreement with the trend

revealed by the two-electrode system. Interestingly, the specific capacitance of PANI/CFs

with 50 mM ANI dramatically goes down to 72 F g-1 at 100 mV/s. According to the SEM and

TEM images of PANI/CFs, we know that it is due to the self-aggregation of ANI. This result

further confirms the conclusion that the ordered whisker-like nanostructure and the synergistic

effect of the two composites are responsible for the electrochemical stability.

Figure S1c and S1d show the charge-discharge curves in the potential window -0.2 to 0.8 V

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0 500 1000 1500 2000 2500

-0.2

0.0

0.2

0.4

0.6

0.8

10 mM 25 mM 50 mM5 mM

Vol

tage

/ V

Time/s

5 mM 10 mM 25 mM 50 mM

0 100 200 300 400 500 600

-0.2

0.0

0.2

0.4

0.6

0.8

50 mM 10 mM 25 mM 5 mM

Vol

tage

/ V

Time/ s

5 mM 10 mM 25 mM 50 mM

0.00 0.02 0.04 0.06 0.08 0.10

100

200

300

400

500

600

Sp

ecif

ic C

apac

itan

ce/ F

g-1

Current density/ A g-1

5 mM 10 mM 25 mM 50 mM

-0.2 0.0 0.2 0.4 0.6 0.8-0.04

-0.02

0.00

0.02

0.04

O2

R1

R2

O1

25 mM50 mM

10 mM

5 mM

Cu

rren

t/ A

Voltage/ V

(a) (b)

(c) (d) Scan rate/ V s-1

of PANI/CFs with different initial ANI concentration at the current density of 0.2 and 1 A g-1.

The curves are nearly linear and symmetric, indicating an ideal capacitor behavior, in

agreement with the results of two-electrode system (in the main text).

Figure S1 The electrochemical capacitance performance of PANI/CFs nanocomposites with

different concentration of aniline: 5, 10, 25, and 50 mM. a) Cycle voltammetry within the

potential window -0.2 to 0.8 V at the scan rates of 10 mV/s; b) Specific capacitance of

PANI/CFs prepared with different initial aniline concentration: 5, 10, 25, and 50 mM at

different current densities; c) Galvanostatic charge-discharge tests within the potential

window -0.2 to 0.8 V at the current density of 0.2 A g-1; d) Galvanostatic charge-discharge

tests within the potential window -0.2 to 0.8 V at the current density of 1 A g-1. The

electrolyte is 1 M H2SO4.

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Figure S2. SEM images of the PANI/CFs nanocomposites with different concentration of aniline: (a) 5 mM; (b) 10 mM; (c) 25 mM; and (d) 50mM. Other conditions: aniline/APS=1/1 (molar ratio), CF =0.3 mg ml-1, and the reaction was carried out 0 ℃ for 7 h.

220 nm

453 nm

302nm

378 nm

a b

c d

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-0.2 0.0 0.2 0.4 0.6 0.8

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

Cu

rren

t / A

Voltage/ V

5 mv/s 10 mv/s 20 mv/s 50 mv/s 100 mv/s

(c) -0.2 0.0 0.2 0.4 0.6 0.8

-0.04

-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

Cu

rren

t / A

Voltage/ V

5 mv/s 10 mv/s 20 mv/s 50 mv/s 100 mv/s

(b)

(d)

-0.2 0.0 0.2 0.4 0.6 0.8-0.10

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

Cu

rren

t / A

Voltage/ V

5 mv/s 10 mv/s 20 mv/s 50 mv/s 100 mv/s

-0.2 0.0 0.2 0.4 0.6 0.8-0.07-0.06-0.05-0.04-0.03-0.02-0.010.000.010.020.030.040.050.060.07

Cu

rren

t / A

Voltage/ V

5 mv/s 10 mv/s 20 mv/s 50 mv/s 100 mv/s

(a)

Figure S3. The Cyclic voltammetry curves of PANI/CFs with different aniline concentration at different scan rate: 5, 10, 20, 50, and 100 mV/s: (a) 5 mM; (b) 10 mM; (c) 25 mM; and (d) 50 mM. Table S1 The amount of PANI/CFs coated on stain steel and percentage of CFs and PANI in the resulting PANI/CFs composites

Samples Weight percentage of CFs in the composite (%)

Weight percentage of PANI in the composite (%)

Amount of PANI/CFs coated on stainless (g)

5 mM 58.94 41.06 0.00602

10 mM 41.96 58.04 0.00423

25 mM 16.20 83.80 0.00560

50 mM 9.11 90.89 0.00602

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