)URQWLHUV MRXUQDOLV WKH 3DUWQHU 2UJDQLVDWLRQV · After 1000 cycles CV-Z" (ohm) Z' (ohm) Fig. S12. Electrochemical testing of Fe-Co3O4 while the immersion concentration is 0.03 M (a)

Supporting information for

Remarkably improved oxygen evolution reaction activity of

cobalt oxides by Fe ion solution immersion process

Shencheng Pan1, Xin Mao2, Juan Yu1, Lin Hao5, Aijun Du2, Bing Li1,3,4,5,*

1. School of Physics and Electronic Information, Huaibei Normal University, Huaibei

235000, P. R. China

2. School of Chemistry and Physics and Center for Material Science, Queensland University

of Technology, Gardens Point Campus, Brisbane, QLD 4001, Australia

3. Anhui Province Key Laboratory of Pollutant Sensitive Materials and Environmental

Remediation, Huaibei Normal University, Huaibei 235000, P. R. China

4. Information College, Huaibei Normal University，Huaibei 235000, P. R. China

5. Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee

37996, USA

* Corresponding author. E-mail: [email protected]

200 400 600 800 1000 200 400 600 800 1000

(b)

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1)

Co3O4

Fe-Co3O

4

(a)

Inte

nsi

ty (

a.u

.)

Raman shift (cm-1)

CoO

Fe-CoO

Fig. S1. Raman spectra of Co3O4, CoO, Fe-Co3O4 and Fe-CoO.

Electronic Supplementary Material (ESI) for Inorganic Chemistry Frontiers.This journal is © the Partner Organisations 2020

Fig. S2. TEM images of -Co(OH)2 nanoflower.

Fig. S3. TEM images of Co3O4 nanoparticles before Fe ion treatments.

Fig. S4. TEM images of CoO nanoparticles before Fe ion treatments.

Fig. S5. (a) High resolution TEM images of Fe-Co3O4, (b) the SAED pattern of Fe-Co3O4.

Fig. S6. (a) High resolution TEM images of Fe-CoO, (b) the SAED pattern of Fe-CoO.

Fig. S7. SEM image (a), elemental mapping of Co (b), O (c) and Fe (d) element in Fe-Co3O4.

Fig. S8. SEM image (a), elemental mapping of Co (b), O (c) and Fe (d) element in Fe-CoO.

810 800 790 780 810 800 790 780

810 800 790 780810 800 790 780

(d)(c)

Co3O

4

Fe-Co3O

4

Co 2p1/2

Co 2p3/2

Co 2p

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

(b)

Co 2p1/2

Co 2p3/2

Co 2p

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

CoO

Fe-CoO(a)

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

CoO

Co2+

Co2+

Co 2p3/2

Co 2p1/2

sat.

sat.

Co3+

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

Co3O

4

Co2+

Co3+

sat.sat.

Co2+

Co 2p3/2

Co 2p1/2

Co3+

Ratio: 56.5%

Fig. S9. (a) High resolution XPS spectrum of Co3O4 and Fe-Co3O4. (b) High resolution XPS

spectrum of CoO and Fe-CoO. (c) Fitting of Co 2p XPS spectrum for Co3O4, (d) fitting of Co 2p

XPS spectrum for CoO.

1.2 1.4 1.6 1.8

0

100

200

300

1.45

1.50

1.55

1.60

1.65

1.70

0.5 1.0 1.5

Cu

rren

t D

ensi

ty (

mA

/cm

2)

Potential (V vs. RHE)

Fe-Co3O

4

Fe-CoO

RuO2

NF

Log[J/(mA/cm2)]

Pote

nti

al (

V v

s. R

HE

)

Fe-Co3O

4

Fe-CoO

RuO2

NF

152 mV/dec

142 mV/dec

55 mV/dec

55 mV/dec

1 2 3 4200

300

400

500

(c)

(b)J=10 mA/cm

2

Over

po

ten

tial

(m

V)

Samples

280 mV296 mV

306 mV

451 mV

(a)

Fig. S10. (a) LSV curves of Fe-Co3O4, Fe-CoO, RuO2 and no-load Ni foam. (b) Overpotential

comparison histogram of Fe-Co3O4, Fe-CoO, RuO2 and no-load Ni foam at a current density of

10 mA/cm2. (c) Corresponding Tafel plots of the four prepared catalysts.

1.2 1.4 1.6 1.8

0

50

100

150

200

0 10 20 30 40 50 60 700

10

20

30

40

50 Initial

After 1000 cycles CV

Cu

rren

t D

ensi

ty (

mA

/cm

2)


326 mV 343 mV

(b)

-Z"

(oh

m)

Z' (ohm)

Initial


(a)

Fig. S11. Electrochemical testing of Fe-Co3O4 while the immersion concentration is 0.01 M (a)

LSV curves, (b) Nyquist plots with an initial and after 1000 cycles CV test.

1.2 1.4 1.6 1.8

0

50

100

150

200

0 10 20 30 40 500

5

10

15

20

25

30(b) Initial


Cu

rren

t D

ensi

ty (

mA

/cm

2)


314 mV325 mV

(a) Initial


-Z"

(oh

m)

Z' (ohm) Fig. S12. Electrochemical testing of Fe-Co3O4 while the immersion concentration is 0.03 M (a)


1.2 1.4 1.6 1.8

0

50

100

150

200

0 10 20 30 40 50 60 700

10

20

30

40

(b) Initial


Cu

rren

t D

ensi

ty (

mA

/cm

2)


323 mV331 mV

(a) Initial


-Z"

(oh

m)

Z' (ohm) Fig. S13. Electrochemical testing of Fe-Co3O4 while the immersion concentration is 0.04 M (a)


1.2 1.4 1.6 1.8

0

50

100

150

200

0 10 20 30 40 50 60 70 800

10

20

30

40

50

60(b) Initial


Cu

rren

t D

en

sity

(m

A/c

m2)


381 mV 387 mV

(a)

Initial


-Z"

(ohm

)

Z' (ohm)

Fig. S14. Electrochemical testing of Fe-CoO while the immersion concentration is 0.1 M (a) LSV

curves, (b) Nyquist plots with an initial and after 1000 cycles CV test.

1.2 1.4 1.6 1.8

0

50

100

150

200

0 10 20 30 40 50 60 700

10

20

30

40

50(b)

340 mV

Initial


Cu

rren

t D

ensi

ty (

mA

/cm

2)


319 mV

(a) Initial


-Z"

(oh

m)

Z' (ohm)

Fig. S15. Electrochemical testing of Fe-CoO while the immersion concentration is 0.03 M (a)


-0.6 -0.4 -0.2 0.0 1.2 1.4 1.6 1.8-400

-200

0

200

400

0.4 0.6 0.8 1.0 1.2 1.4

-0.25

-0.20

-0.15

-0.10

HER

=168 mV

HER

=224 mV

OER

=296 mV

Fe-Co3O

4

Fe-CoOC

urr

ent

Den

sity

(m

A/c

m2)


OER

=280 mV

Pote

nti

al (

V v

s. R

HE

)

Log[J/(mA/cm2)]

Fe-Co3O

4

Fe-CoO

114 mV/dec

160 mV/dec

Tafel slope of HER(a) (b)

Fig. S16. (a) OER and HER curve of Fe-Co3O4 and Fe-CoO, (b) Tafel plots of Fe-Co3O4 and

Fe-CoO.

0.00 0.02 0.04 0.06 0.08 0.10-0.2

-0.1

0.0

0.1

0.2

0.00 0.02 0.04 0.06 0.08 0.10

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.00 0.02 0.04 0.06 0.08 0.10-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.00 0.02 0.04 0.06 0.08 0.10-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

Cu

rren

t D

ensi

ty (

mA

/cm

2)

Potential (V vs. AgCl)

Scan rate Scan rate

Cu

rren

t D

ensi

ty (

mA

/cm

2)


Scan rate

Cu

rren

t D

ensi

ty (

mA

/cm

2)


Scan rate(d)(c)

(b)

Cu

rren

t D

ensi

ty (

mA

/cm

2)


(a)

Fig. S17. CVs of Co3O4 (a), Fe-Co3O4 (b), CoO (c) and Fe-CoO (d) with increasing scan rates.

Fig. S18. SEM image (a), elemental mapping of Co (b), O (c) and Fe (d) element in Fe-Co3O4

after i-t test.

Fig. S19. SEM image (a), elemental mapping of Co (b), O (c) and Fe (d) element in Fe-CoO after

i-t test.

735 730 725 720 715 710 705 810 800 790 780 534 532 530 528

735 730 725 720 715 710 705 810 800 790 780 534 532 530 528

Fe 2p

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

After

Before

Co 2p

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

After

Before

O 1s

(d)

(c)(b)

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

After

Before

(a)

Fe 2p(f)(e)

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

After

Before

Co 2p

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

After

Before

O 1s

Inte

nsi

ty (

a.u.)

Binding Energy (eV)

Before

After

Fig. S20. High-resolution XPS spectrum of Fe 2p (a), Co 2p (b) and O 1s (c) for Fe-Co3O4 and Fe

2p (d), Co 2p (e) and O 1s (f) for Fe-CoO before (black line) and after (red line) i-t test.

0 5 10 15 20 25 300

5

10

15

20

0 10 20 30 400

5

10

15

20

25

30 Initial


-Z"

(oh

m)

Z' (ohm)

Fe-Co3O

4 Fe-CoO

(b) Initial


-Z"

(oh

m)

Z' (ohm)

(a)

Fig. S21. Nyquist plots of Fe-Co3O4 (a) and Fe-CoO (b) for initial and after 1000 cycles CV test.

0.00 0.02 0.04 0.06 0.08 0.10

-0.8

-0.4

0.0

0.4

0.8

20 40 60 80 100 120 140 160

0.2

0.4

0.6

0.8

1.0

1.2

1.4

Cu

rren

t D

ensi

ty (

mA

/cm

2)


Scan rate (b)

J

(mA

/cm

2)

Scan rate (mV/s)

3.92 mF/cm2

(a)

Fig. S22. (a) CV of Fe-Co3O4 with increasing scan rates after CV cycles (b) Cdl calculated value

of Fe-Co3O4 after CV cycles.

0.00 0.02 0.04 0.06 0.08 0.10

-0.8

-0.4

0.0

0.4

0.8

20 40 60 80 100 120 140 1600.2

0.4

0.6

0.8

1.0(b)

Scan rate

Cu

rren

t D

ensi

ty (

mA

/cm

2)


(a)

2.6 mF/cm2

J

(mA

/cm

2)

Scan rate (mV/s)

Fig. S23. (a) CV of Fe-CoO with increasing scan rates after 1000 CV cycles (b) Cdl calculated

value of Fe-CoO after CV cycles.

Table S1 The electrocatalytic OER activity of Fe-Co3O4 by different Fe ion concentrations in

soak solution

Fe ion concentrations in

soak solution

Overpotential

(mV)

Current density

@1.8 V (mA/cm2)

Charge transfer

resistance (Ω)

0.01 M (Initial) 343 (10 mA/cm2) 294 45.7

0.01 M (After 1000 CV) 326 (10 mA/cm2) 296 62.5

0.02 M (Initial) 280 (10 mA/cm2) 542 22.6

0.02 M (After 1000 CV) 263 (10 mA/cm2) 597 26.6

0.03 M (Initial) 325 (10 mA/cm2) 303 27.8

0.03 M (After 1000 CV) 314 (10 mA/cm2) 349 43.8

0.04 M (Initial) 331 (10 mA/cm2) 285 35.2

0.04 M (After 1000 CV) 323 (10 mA/cm2) 303 60.4

Table S2 The electrocatalytic OER activity of Fe-CoO by different Fe ion concentrations in soak

solution

Fe ion concentrations in

soak solution

Overpotential

(mV)

Current density

@1.8 V (mA/cm2)

Charge transfer

resistance (Ω)

0.01 M (Initial) 387 (50 mA/cm2) 365 41.9

0.01 M (After 1000 CV) 381 (50 mA/cm2) 398 63.8

0.02 M (Initial) 296 (10 mA/cm2) 480 29.6

0.02 M (After 1000 CV) 272 (10 mA/cm2) 539 33.1

0.03 M (Initial) 340 (10 mA/cm2) 269 51.4

0.03 M (After 1000 CV) 319 (10 mA/cm2) 354 62.5

Table S3 Comparison of OER performance of some cobalt oxide based electrocatalysts in

recently work.

Sample Electrolyte Current density

(mA/cm2) (mV)

Tafel slope

(mV/dec)

Fe-Co3O4 (This work) 1 M KOH 10 mA/cm2 280 55

Fe-CoO (This work) 1 M KOH 10 mA/cm2 296 55

RuO2 (This work) 1 M KOH 10 mA/cm2 306 142

Co3O4-MWCNT1 1 M KOH 10 mA/cm2 320 69

Co3O4-B2 1 M KOH 10 mA/cm2 318 57.6

S-CoO/Co3O43 1 M KOH 10 mA/cm2 275 92

Hemoglobin modified

Co3O4-g-C3N44

0.5 M KOH 10 mA/cm2 370 66

Co3O4 nanoflowers5 1 M KOH 10 mA/cm2 297 79.1

Co3O4/CoO6 1 M KOH 10 mA/cm2 302 68.6

References

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Documents

)URQWLHUV MRXUQDOLV WKH 3DUWQHU 2UJDQLVDWLRQV · After 1000 cycles CV-Z" (ohm) Z' (ohm) Fig. S12. Electrochemical testing of Fe-Co3O4 while the immersion concentration is 0.03 M (a)