Page | - 1 -

Supporting Information

Cellulose Derived Graphenic Fibers for Capacitive Desalination of

Brackish Water

Nalenthiran Pugazhenthiran,1 Soujit Sen Gupta,

1 Anupama Prabhath,

1 Muthu Manikandan,

1

Jakka Ravindran Swathy,1 V. Kalyan Raman

2 and Thalappil Pradeep

1,*

1DST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE). Department

of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India.

2Centre of Excellence (Biotechnology) & Water and wastewater Technology, Thermax

Limited, Pune 411019, India

E-mail: pradeep@iitm.ac.in; Fax: +91-44-2257-0545.

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Figure S1. EDS spectrum of the layer-by-layer stacked carbon-graphite electrode before SiO2

etching. Inset: Its corresponding SEM image and elemental mapping images.

C

O Si

Si

C

O

Energy, keV

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Figure S2. EDS spectrum of the layer-by-layer stacked carbon-graphite electrode after

etching SiO2. Inset: SEM and Elemental mapping images.

Energy, keV

C

Si O

C

O

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Figure S3. N2 adsorption–desorption isotherms of graphite-reinforced carbon fiber electrode.

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0 2 4 6 8 10 12 14 16 180

20

40

60

80

100

Cu

rren

t (m

A)

Potential (mV)

-0.8 -0.6 -0.4 -0.2 0.0 0.2-0.25

-0.20

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

Cu

rren

t(A

)

Potential(V)

2 mV/s

10 mV/s

50 mv/s

100 mV/s

200 mV/s

A B

Figure S4:A) I-V curve and B) CV curves of the GrC electrode at varying scan rates

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Figure S5. Electro-adsorption and desorption performance of the graphite-reinforced carbon

fiber electrode in NaCl solution. EDS spectrum and their elemental mapping images of the

regenerated positive terminal carbon-graphite electrode (after first cycle). Note: Aluminum

comes from the SEM sample stubs.

Energy, keV

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Figure S6. Electro-adsorption and desorption performance of the graphite-reinforced carbon

fiber electrode in NaCl solution. EDS spectrum and their elemental mapping images of the

regenerated negative terminal carbon-graphite electrode (after first cycle).

Energy, keV

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Figure S7. Electro-adsorption and desorption performance of the graphite-reinforced carbon

fiber electrode in NaCl solution. EDS spectrum and their elemental mapping images of the

regenerated positive terminal carbon-graphite electrode (after ten consecutive cycle). Note:

Aluminum comes from the SEM sample stubs.

Energy, keV

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Figure S8. Electro-adsorption and desorption performance of the graphite-reinforced carbon

fiber electrode in NaCl solution. EDS spectrum and their elemental mapping images of the

regenerated negative terminal carbon-graphite electrode (after ten consecutive cycle).

Energy, keV

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Figure S9. Plot of CDI results of electro-adsorption and desorption performance of the

graphite-reinforced carbon fiber electrode in different charged species ie., Na+, Mg

2+ and

Fe3+

.

Time (min)

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Energy, keV

O

C

CaMg

MgO Ca

C0 20 40 60 80 100 1200.6

0.7

0.8

0.9

1.0

0 20 40 60 80 100 120

Electro-desorption

Electro-adsorption

Time (min)

Ct/C

0

0.0

0.1

0.2

0.3

0.4

1-(C

0 /Ct )

Figure S10. Electro-adsorption and electro-desorption performance of the graphite-

reinforced carbon fiber electrode in MgCl2 solution. EDS spectrum and their elemental

mapping images of the negative terminal after electro-adsorption of the carbon-graphite

electrode. Note: Calcium is from the water used.

C

Page | - 12 -

Energy, keV

FeO

C

C

O Fe

0 20 40 60 80 100 120

0.4

0.6

0.8

1.0

0 20 40 60 80 100 120

Electro-adsorption

Time (min)

Ct/C

0

0.0

0.2

0.4

0.6

Electro-desorption 1-(C

0 /Ct )

Figure S11. Electro-adsorption and desorption performance of the graphite-reinforced carbon

fiber electrode in MgCl2 solution. EDS spectrum and their elemental mapping images of the

positive terminal after electro-adsorption of the carbon-graphite electrode.

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Figure S12. Electro-adsorption and desorption performance of the graphite-reinforced carbon

fiber electrode in FeCl3 solution. EDS spectrum and their elemental mapping images of the

negative terminal after electro-adsorption on the carbon-graphite electrode.

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Figure S13. Electro-adsorption and desorption performance of graphite reinforced carbon

fiber electrode in FeCl3 solution. EDS spectrum and their elemental mapping images of the

positive terminal after electro-adsorption on the carbon-graphite electrode.

C

O Cl

Energy, keV

C

O Cl

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Figure S14. CDI performance of graphite reinforced carbon fiber electrode in the mixed

negative ions (Cl, F

, NO3

, SO4

2) system. EDS spectrum and their elemental mapping

images of the negative terminal after electro-adsorption on the porous carbon-graphite

electrode. Note: Aluminum comes from the SEM sample stubs.

O C

Na

Al

Energy, keV

C

Na O

Page | - 16 -

Figure S15. CDI performance of graphite reinforced carbon fiber electrode in the mixed

negative ions (Cl, F

, NO3

, SO4

2) system. EDS spectrum and their elemental mapping

images of the positive terminal after electro-adsorption on the porous carbon-graphite

electrode which shows the presence of O, Cl, F, N and S. Note: Aluminum comes from the

SEM sample stubs.

Energy, keV

C O Cl

F N S

O

N

C

F S Cl

Al

Page | - 17 -

0.4

0.6

0.8

1.0

0.7

0.8

0.9

1.0

0 20 40 60 80 100 1200.8

0.9

1.0

250 mg/L

500 mg/L

1000 mg/L

Time (min)

C0/C

t

C

B

A

Figure S16. CDI performance of the GrC electrode at different NaCl concentration A) 1000,

B) 500 and C) 250 mg/L. All other parameters are kept constant. This measurement was

performed as it is known that the salt concentrations used to measure the electrosorption

performance influence the observed capacities.