1

Electronic Supplementary information

Co(II)-porphyrins decorated carbon nanotubes as catalysts for oxygen

reduction reactions: An approach for fuel cell improvement†

Piyush Kumar Sonkar1, Kamal Prakash

2, Mamta Yadav

1, Vellaichamy Ganesan*

1, Muniappan

Sankar2, Rupali Gupta

1, Dharmendra Kumar Yadav

1

1Department of Chemistry, Institute of Science

Banaras Hindu University, Varanasi-221 005, UP, India

Telephone: + 91-542-6701609; Fax: + 91-542-2368127

Email: velganesh@yahoo.com and velgan@bhu.ac.in

2Department of Chemistry, Indian Institute of Technology Roorkee,

Roorkee-247667, Uttarakhand, India

* Corresponding author

Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.This journal is © The Royal Society of Chemistry 2017

2

Section S1

Conversion of observed experimental potential to reversible hydrogen electrode, RHE scale

The experimentally observed potentials against Ag/AgCl or saturated calomel electrode, SCE are

converted to the reversible hydrogen electrode (RHE) scale according to the Nernst equation

[SR1-SR3]:

ERHE = EAg/AgCl + 0.059pH + E0Ag/AgCl (1)

ERHE = ESHE + 0.059pH + E0

SHE (2)

where EAg/AgCl is the experimentally measured potential against Ag/AgCl reference electrode and

E0

Ag/AgCl is 0.199 V at 25 ºC. Similarly, ESCE is the experimentally measured potential against

SCE reference and E0

SCE is 0.241 at 25 ºC.

References

[SR1] G. Ferrero, K. Preuss, A. Fuertes, M. Sevilla and M.-M. Titirici, Journal of Materials

Chemistry A, 2016, 4, 2581-2589.

[SR2] A. J. Bard, L. R. Faulkner, J. Leddy and C. G. Zoski, Electrochemical methods:

fundamentals and applications, Wiley New York, 1980.

[SR3] D. Y. Chung, S. W. Jun, G. Yoon, S. G. Kwon, D. Y. Shin, P. Seo, J. M. Yoo, H. Shin,

Y.-H. Chung and H. Kim, Journal of the American Chemical Society, 2015, 137, 15478-

15485.

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Table S1 Composition of MWCNT-CoTHPP, MWCNT-CoTCPP and MWCNT-CoTPP in

different weight ratios and amount of metal complex adsorbed.

Name of the

sample

(MWCNT (in mg)

: metal complex

(in mmoles))

Initial composition added Final composition after adsorption

MWCNT

(mg)

Cobalt

porphyrin

(mg)

% N

(obtained

from

elemental

analysis)

N

calculated

(mg)

Cobalt

porphyrin

calculated

(mg)

MWCNT-CoTHPP

(10:0.02)

10 14.70 1.11 0.266 2.94

MWCNT-CoTPP

(10:0.02)

10 13.42 4.10 1.428 10.065

MWCNT-CoTCPP

(10:0.02)

10 16.94 2.12 0.574 8.47

MWCNT-CoTHPP

(10:0.01)

10 07.35 1.07 0.184 2.205

MWCNT-CoTPP

(10:0.01)

10 06.71 4.14 1.442 6.70

MWCNT-CoTCPP

(10:0.01)

10 08.47 2.03 0.378 5.929

MWCNT-CoTHPP

(10:0.005)

10 03.68 0.65 0.088 1.1025

MWCNT-CoTPP

(10:0.005)

10 03.35 1.19 0.1596 1.878

MWCNT-CoTCPP

(10:0.005)

10 04.24 0.77 0.1092 1.6093

MWCNT (10:0.00) 10 00.00 0.00 0.00 0.000

MWCNT-CoTPP

(10:0.001)

10 0.671 0.56 0.084 0.671

MWCNT-CoTHPP

(10:0.001)

10 0.735 0.52 0.098 0.5145

MWCNT-CoTCPP

(10:0.001)

10 0.847 0.41 0.126 0.5929

4

Fig. S1 IR spectra of the (a) MWCNT, (b) CoTHPP (c) MWCNT-CoTHPP, (d) CoTCPP,

(e) MWCNT-CoTCPP, (f) CoTPP, (g) MWCNT-CoTPP with the KBr pallets.

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C

N

O

Co

C

N O Co

Completespectra

Fig. S2(A) EDAX mapping of MWCNT-CoTHPP composite showing the element

distribution in the material.

6

C

N

O

Co

Completespectra

C

N O Co

Fig. S2(B) EDAX mapping of MWCNT-CoTCPP composite showing the element

distribution in the material.

7

Fig. S2(C) EDAX mapping of MWCNT-CoTPP composite showing the elemental

distribution in the material.

C

N

O

Co

Completespectra

N O Co

C

8

0.1 0.2 0.3

50

60

70

Vo

lum

e @

ST

P (

cc/g

)

Relative Pressure, P/P0

MWCNT-CoTHPP

MWCNT

MWCNT-Co-TCPP

MWCNT-CoTPP

Fig. S3 Plot showing the nitrogen adsorption with MWCNT, MWCNT-CoTHPP,

MWCNT-CoTCPP and MWCNT-CoTPP materials.

9

Fig. S4 CV response of GC/MWCNT-CoTHPP (a), GC/MWCNT-CoTCPP (b) and

GC/MWCNT-CoTPP (c) at different scan rates 20, 50, 75, 100, 200, 300, 400,

500 mVs-1

in 0.1 M HClO4. (a’-c’) represents the respective plot of anodic (Ipa)

and cathodic (Ipc) peak current vs square root of scan rate.

0.0 0.4 0.8

-40

0

40

Cu

rren

t / A

E/V (vs RHE)

0.0 0.3 0.6 0.9

-40

0

40

80

Cu

rren

t / A

E/V (vs RHE)6 9 12 15 18

-6

2

4

C

urr

en

t / A

1/2

/ (mV/s)1/2

0.0 0.4 0.8-200

-100

0

100

200

Cu

rren

t / A

E/V (vs RHE)

6 9 12 15 18

-10

0

10

20

Cu

rren

t / A

1/2

/ (mV/s)1/2

4 8 12 16 20

-8

-4

0

4

Cu

rren

t / A

1/2

/ (mV/s)1/2

a a’

b b’

c c’

10

0.0 0.3 0.6

-0.6

-0.3

0.0

0.3

j/m

Acm

-2

E/V (vs RHE)0.0 0.4 0.8

-0.6

-0.3

0.0

0.3

j/m

Acm

-2

E/V (vs RHE)0.0 0.4 0.8

-0.6

-0.3

0.0

0.3

j/m

Acm

-2

E/V (vs RHE)0.2 0.4 0.6 0.8

-0.6

-0.3

0.0

0.3

j/m

Acm

-2

E/V (vs RHE)0.0 0.3 0.6

-0.6

-0.3

0.0

0.3

j/m

Acm

-2

E/V (vs RHE)

0.0 0.5 1.0

-1.8

-1.2

-0.6

0.0

j/m

Acm

-2

E/V (vs RHE)

0.0 0.4 0.8 1.2

-1.8

-1.2

-0.6

0.0

j/m

Acm

-2

E/V (vs RHE)

0.0 0.3 0.6 0.9 1.2

-1.8

-1.2

-0.6

0.0

j/m

Acm

-2

E/V (vs RHE)0.0 0.4 0.8 1.2

-1.8

-1.2

-0.6

0.0

j/m

Acm

-2

E/V (vs RHE)

0.6 0.8 1.0

-1.6

-0.8

0.0

j/m

Acm

-2

E/V (vs RHE)0.6 0.8 1.0

-1.6

-0.8

0.0

j/m

Acm

-2

E/V (vs RHE)0.6 0.8 1.0

-1.6

-0.8

0.0

j/m

Acm

-2

E/V (vs RHE)0.6 0.8 1.0

-1.6

-0.8

0.0

j/m

Acm

-2E/V (vs RHE)

0.4 0.8 1.2 1.6

-1.6

-0.8

0.0

j/m

Acm

-2

E/V (vs RHE)

ca b d e

a’ b’ c’ d’ e’

a” b” c” d” e”

0.0 0.4 0.8 1.2

-1.8

-1.2

-0.6

0.0

j/m

Acm

-2

E/V (vs RHE)

0.2 0.4 0.6 0.8 1.0

-0.6

-0.3

0.0

0.3

E / V (vs RHE)

e

Fig. S5 CV response of GC/MWCNT-CoTHPP (a, a’ and a”), GC/MWCNT-CoTCPP (b, b’ and b”), GC/MWCNT-CoTPP (c,

c’ and c”), GC/MWCNT (d, d’ and d”) and GC/Pt-C (e, e’ and e”) electrodes in 0.1 M HClO4 (a to e), 0.1 M PBS, pH

7.0 (a’ to e’) and in 0.1 M KOH (a” to e”) solutions saturated with either nitrogen (dashed line) or oxygen (solid line).

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-0.3 0.0 0.3 0.6 0.9

-0.20

-0.10

0.00

0.10

GC/CoTPP

GC/CoTHPP

GC/CoTCPP

j/m

Acm

-2

E/V (vs RHE)

0.6 0.8 1.0

-0.3

-0.2

-0.1

0.0

GC/CoTHPP

GC/CoTCPP

GC/CoTPP

j/m

Acm

-2

E/V (vs RHE)

a b

c

0.0 0.3 0.6 0.9 1.2

-0.3

-0.2

-0.1

0.0

j/m

Acm

-2

E/V (vs RHE)

GC/CoTCPP

GC/CoTHPP

GC/CoTPP

Fig. S6 CV response of different cobalt porphyrins films based electrodes in 0.1 M HClO4

(a), 0.1 M PBS pH 7.0 (b) and 0.1 M KOH (c) in oxygen saturated condition with

the scan rate of 20 mVs-1

.

12

-0.2 0.0 0.2 0.4 0.6

-100

0

100 dc

ba

Cu

rren

t / µ

A

Potential / V (vs Ag/AgCl)

Fig. S7 CV response in 0.1 M KCl with 10.0 mM K3[Fe(CN)6]/K4[Fe(CN)6] (1:1) for

active surface area determination. Where, a, b, c and d stands for GC/MWCNT-

CoTHPP, GC/MWCNT-CoTCPP, GC/MWCNT-CoTPP, and GC/MWCNT,

respectively.

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0.0 0.3 0.6

-4

-3

-2

-1

0

j/m

Acm

-2

E/V (vs RHE)

0.0 0.3 0.6 0.9-4

-3

-2

-1

0

j/m

Acm

-2

E/V (vs RHE)

0.0 0.3 0.6

-4

-3

-2

-1

0

j/m

Acm

-2

E/V (vs RHE)

0.02 0.04 0.06 0.08 0.100.2

0.4

0.6

0.8

1.0

1.2

j-1/m

Acm

-2

1/1/2

(rpm)1/2

0.02 0.04 0.06 0.08 0.10

0.4

0.8

1.2

1.6

j-1/m

Acm

-2

1/

(rpm)1/2

0.02 0.04 0.06 0.08 0.10

0.4

0.8

1.2

1.6

j-1/m

Acm

-2

1/1/2

(rpm)1/2

A B C

DE F

0

2500 rpm

0

2500 rpm

0

2500 rpm

Fig. S8 Current-potential curves at different rotation rates in 0.1 PBS pH 7.0 at a scan rate

of 10 mVs-1

in oxygen saturated condition (A-C) and the respective Koutecky-

Levich plots (D-F) for GC/MWCNT-CoTHPP (A, D), GC/MWCNT-CoTCPP (B,

E) and GC/MWCNT-CoTPP (C, F).

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0.4 0.6 0.8

-4

-2

0

j / m

Acm

-2

E/V (vs RHE)0.4 0.6 0.8 1.0

-4

-2

0

j/m

Acm

-2

E/V (vs RHE)

0.025 0.030 0.035 0.040

0.35

0.40

0.45

0.50

j-1/m

Acm

-2

1/

(rpm)1/2

0.02 0.03 0.04

0.3

0.4

0.5

j-1/m

Acm

-2

1/

(rpm)1/2

0.03 0.06 0.09

0.3

0.6

0.9

j-1/m

Acm

-2

1/1/2

(rpm)1/2

A B

D E

0.4 0.6 0.8 1.0 1.2

-4.0

-2.0

0.0

j/m

Acm

-2

E/V (vs RHE)

F

C

300

2500 rpm

300

2500 rpm

300

2500 rpm

Fig. S9 Current-potential curves at different rotation rates in 0.1 M KOH at a scan rate of

10 mVs-1

in oxygen saturated condition (A-C) and the respective Koutecky-

Levich plots (D-F) for GC/MWCNT-CoTHPP (A, D), GC/MWCNT-CoTCPP (B,

E) and GC/MWCNT-CoTPP (C, F).

15

-0.3 0.0 0.3 0.6

-4

-3

-2

-1

0

j/m

Acm

-2

E/V (vs RHE)

-0.3 0.0 0.3 0.6-4

-2

0

j/m

Acm

-2

E/V (vs RHE)

-0.4 -0.2 0.0 0.2 0.4 0.6

-3

-2

-1

0

j/m

Acm

-2

E/V (vs RHE)

0.0 0.2 0.4 0.6 0.8 1.0-4

-3

-2

-1

0

j/m

Acm

-2

E / V (vs RHE)

a b

c d

Fig. S10 LSV response for the stability of GC/MWCNT-CoTHPP (a), GC/MWCNT-

CoTCPP (b), GC/MWCNT-CoTPP (c) and GC/Pt-C (d) electrodes for ORR (at

1600 rpm) in 0.1 M HClO4 at the scan rate of 100 mVs-1

. Dotted lines represent

the first LSV response while solid lines represent LSV response after 3000 CV

cycles under the same conditions.

16

2θ / degree 2θ / degree

2θ / degree

A B

20 40 600

400

800

a'

a

Inte

nsit

y

20 40 600

400

800

b'

b

Inte

nsit

y

C

20 40 600

400

800

c'

c

Inte

nsit

y

Fig. S11 XRD patterns of MWCNT-CoTHPP (A), MWCNT-CoTCPP (B) and MWCNT-

CoTPP (C) on ITO plates (thin film of the respective material is coated on ITO

plates) before (a, b, c) and after (a’, b’, c’) stability test (3000 CV cycles).

17

a b c

a’ b’ c’

1 μm

1 μm

1 μm

1 μm

1 μm

1 μm

Fig. S12 SEM images of MWCNT-CoTHPP (a, a’), MWCNT-CoTCPP (b, b’) and

MWCNT-CoTPP (c, c’) on ITO plates (thin film of the respective material is

coated on ITO plates) before (a, b, c) and after (a’, b’, c’) stability test (3000 CV

cycles).