Highly Efficient Oxygen Reduction Catalysts by

Supporting Information

Highly Efficient Oxygen Reduction Catalysts by Rational Synthesis of Nanoconfined Maghemite in a Nitrogen-Doped Graphene Framework Kaipei Qiu,*,† Guoliang Chai,† Chaoran Jiang,‡ Min Ling,† Junwang Tang,‡ and Zhengxiao Guo*,†

† Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK ‡ Department of Chemical Engineering, University College London, Torrington Place, London, WC1E 7JE, UK KEYWORDS Oxygen Reduction Reaction, Hierarchical Graphene Framework, Nitrogen Doping, Maghemite, Alkaline Electrolyte Corresponding Author * (K.Q.) Email: [email protected] * (Z.G.) Email: [email protected]

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a

b

c

d

Figure S1. (a) Raman spectra of GO, GF_800, GF+N1_800, GF+N2_800, and GF+N5_800. XPS (b) C1s spectra for GF, GF+N2, GF_800 and GF+N2_800; and (c) N1s spectra for GF+N+Fe_800. (d) SEM image and Fe mapping of GF+N1+Fe1_800,.

Table S1. BET SSA and total PV of GF+N+Fe_800.

Samples GF+N2+Fe1_800 GF+N2+Fe3_800 GF+N2+Fe5_800 GF+N1+Fe1_800

BET SSA (m2 g-1) 450.1 357.6 217.0 352.0

Total PV (cc g-1) 1.435 1.055 0.657 1.198

2

a

b

400 RPM 800 RPM 1200 RPM 1600 RPM 2000 RPM

c


d



e

f


g


h



3

j

i



Figure S2. LSV plots of (a) GF_800, (b) GF+N1_800, (c) GF+N2_800, (d) GF+N5_800, (e) GF+N2+Fe1_800, (f) GF+N2+Fe3_800, (g) GF+N2+Fe5_800, (h) GF+N1+Fe1+800, (i) PtC and (j) GF+N2+Pt1_800.

a

b

c

d

4

e

f

g

h

Figure S3. K-L plots between 0.4 to 0.65 V vs. RHE for (a) GF+N1_800, (b) GF+N2_800, (dc) GF+N5_800, (d) GF+N2+Fe1_800, (e) GF+N2+Fe3_800, (f) GF+N1+Fe1+800, (g) PtC and (h) GF+N2+Pt1_800.

Figure S4. Comparison of K-L plots at 0.65V vs. RHE.

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Figure S5. RRDE measurement of GF+N2_800, GF+N2+Fe1_800, GF+N2+Pt1_800 and PtC.

Figure S6. Tafel plots of GF+N2+Pt1_800 and GF+N2+Fe1_800

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Table S2. Summary of the electro-catalytic ORR activities for GF+N_800, GF+N+Fe_800, GF+N2+Pt1_800 and PtC.

Sample

P @ -0.5 mA cm-2 (V vs. RHE)

P @ -3 mA cm-2 (V vs. RHE)

ETN @ 0.65 V (n)

GF_800

0.743

0.513

2.43

8.31

GF+N1_800

0.830

0.745

4.04

31.65

GF+N2_800

0.834

0.785

4.00

60.24

GF+N5_800

0.796

0.702

3.83

17.21

GF+N2+Fe1_800

0.907

0.846

4.05

454.55

GF+N2+Fe3_800

0.822

0.796

3.98

94.34

GF+N2+Fe5_800

0.837

0.740

4.51

N/A

GF+N1+Fe1_800

0.880

0.795

3.99

99.90

GF+N1+Fe1_800_W

0.824

0.732

4.06

23.64

GF+N2+Pt1_800

0.903

0.852

4.00

PtC

0.917

0.819

4.03

JK @ 0.65 V (mA cm-2)

H2O2 % @ 0.8V (%)

JK @ 0.8 V (mA cm-2)

Tafel Slope (mV dec-1)

0.7

3.24

47.9

0.31

34.3

66.3

331.81

0.57

46.4

68.1

71.43

4/57

10.96

83.5

Figure S7. LSV of GF+N2+Fe1_800 before and after 5000 scans at 1600 RPM.

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Table S3. Comparison of ORR activities with the existing Fe based catalysts. (1-2) Onset and half-wave potentials are defined as the potential when current density reaches 0.5 or 3 mA cm-2, respectively; and (3) the value of shift is calculated based on the catalyst loading ratio. Catalyst Raw Data (Commercial PtC) Name of Catalyst

Type of Fe species

Catalyst Adjusted Data

Loading (mg cm-2)

Onset (V vs. RHE)

Half-wave (V vs. RHE)

Shift (V)

Onset (V vs. RHE)

Half-wave (V vs. RHE)

Ref

1

2

3

g-FePc

FePc

0.04 (0.1)

0.942 (0.921)

0.875 (0.826)

-0.013

0.929

0.862

6a

FePc-Py-CNT

FePc

0.318 (0.318)

0.956 (0.987)

0.908 (0.866)

-0.084

0.872

0.824

6b

(G-dye 50 wt%-FeP)n

FeN4

0.159

0.817

0.382

-0.021

0.796

0.361

6c

CNTs@Fe-N-C-700

FeN4

0.38 (0.05)

0.895 (0.905)

0.793 (0.803)

-0.029

0.866

0.764

6d

HNCS71

FeN4

0.5 (0.5)

0.890 (0.914)

0.819 (0.831)

-0.011

0.879

0.808

6e

Fe-N/C-800

Fe-Nx

0.1 (0.1)

0.902 (0.928)

0.809 (0.809)

-0.025

0.877

0.784

4c

Carbon nanoshell

Fe-Nx

0.1 (0.1)

0.915 (0.904)

0.836 (0.804)

0.084

0.888

0.788

4a

Fe-N-GC-900

Fe-Nx

0.2 (0.1)

0.935 (0.905)

0.846 (0.809)

-0.010

0.925

0.836

4b

Fe/N/GR-50-(0.10)

Fe-N

0.21 (0.21)

0.994 (0.982)

0.882 (0.900)

-0.079

0.915

0.803

6f

rGFe-800a

Fe-N

0.6 (0.24)

0.848 (0.848)

0.685 (0.767)

0.026

0.874

0.711

6g

Fe/N/CNT@PCF

Fe-N

?

0.856

0.732

N/A

0.856

0.732

4d

FexN/NGA

FexN

0.05 (0.05)

0.906 (0.887)

0.822 (0.816)

0.016

0.922

0.838

7a

FeN/Fe2N

0.6 (0.1)

0.916 (0.922)

0.836 (0.843)

-0.060

0.856

0.776

7b

Fe3C@NG-800

Fe3C

0.4 (0.1)

0.929 (0.929)

0.856 (0.830)

-0.050

0.879

0.806

8a

Fe-N-CNFs

Fe3C

0.6 (0.1)

0.896 (0.938)

0.814 (0.830)

-0.076

0.820

0.738

8b

PMF-800

Fe3C

1.2 (0.125)

0.950 (0.895)

0.858 (0.806)

-0.080

0.870

0.778

8c

N_Fe27

Fe3C

0.8 (0.05)

0.949 (0.911)

0.869 (0.826)

-0.070

0.879

0.799

8d

Fe3C-GNR

Fe3C

0.141 (0.141)

0.852 (0.942)

0.708 (0.832

-0.039

0.813

0.669

8e

Fe/N/G

Fe3C

0.6 (0.6)

0.959 (0.972)

0.842 (0.876)

-0.069

0.890

0.773

8f

Fe3C/NCNTs/OBP-900

Fe3C

0.4 (0.2)

0.947 (0.941)

0.869 (0.844)

-0.054

0.893

0.815

8g

MF50-E

Fe3C

?

0.871

0.776

N/A

0.765

0.760

8h

BP-NFe

Fe3O4

0.39 (0.15)

0.992 (0.939)

0.909 (0.842)

-0.056

0.936

0.853

9a

r-Fe2O3

0.5 (0.5)

0.892 (0.880)

0.809 (0.774)

0.023

0.915

0.832

9b

Fe3O4

?

0.728

0.356

N/A

0.712

0.340

9c

N-CNT/N-G

Fe-CNT-PA Fe3O4@N-GA

8

Fe-N-CIG

Fe3O4

0.23

0.915

0.812

-0.027

0.888

0.785

9d

a-Fe2O3

0.17

0.783

0.555

-0.022

0.761

0.533

9e

Fe3O4

0.6 (0.3)

0.834 (0.883)

0.607 (0.774)

-0.004

0.830

0.603

9f

NG/Fe5.0

Fe

0.051 (0.51)

0.912 (0.888)

0.591 (0.272)

0.015

0.927

0.606

10a

N-graphene/CNTs

Fe

0.424 (0.424)

0.820 (0.837)

0.692 (0.636)

0.066

0.886

0.758

10b

O-NiCoFe LDH

0.12

0.714

0.601

-0.018

0.696

0.583

11a

CuFe

CuFe

0.389 (0.318)

0.976 (1.029)

0.898 (0.921)

-0.132

0.844

0.766

11b

FeCo/C_800

FeCo

0.2 (0.1)

0.927 (0.921)

0.804 (0.804)

-0.026

0.901

0.778

11c

Fe3Co-Rgo

Fe3Co

1.192 (0.1)

0.984 (0.979)

0.865 (0.898)

-0.166

0.818

0.699

11d

Fe/Fe3C-melamine/N-KB

Fe/Fe3C

0.286 (0.143)

0.864 (0.924)

0.756 (0.831)

-0.033

0.831

0.723

12a

CNPs

Fe/Fe3C

0.385 (0.385)

0.982 (0.976)

0.884 (0.856)

-0.073

0.909

0.811

12b

Fe2O3/Fe3O4/FeNx

0.25 (0.25)

0.959 (0.990)

0.867 (0.897)

-0.087

0.872

0.780

12c

Fe3C/C-700

Fe/Fe3C

0.6 (0.25)

0.784 (0.902)

0.665 (0.816)

-0.028

0.756

0.637

12d

N-Fe/Fe3C@C/RGO

Fe/Fe3C

0.707 (0.707)

1.012 (1.012)

0.948 (0.950)

-0.109

0.903

0.839

12e

Fe3N/Fe3O4/CFe15.1@C

0.51 (0.061)

0.954 (0.937)

0.877 (0.850)

-0.071

0.883

0.806

12f

Fe3C/Fe-Nx

0.1 (0.1)

0.861 (0.861)

0.726 (0.770)

0.042

0.903

0.768

12g

Fe/Fe2O3

0.39 (0.39)

0.904 (0.885)

0.768 (0.806)

0.018

0.922

0.786

12h

FeNx/Fe3C/Fe

0.6 (0.15)

0.928 (0.972)

0.822 (0.875)

-0.106

0.822

0.716

12i

Fe/Fe3O4

0.4 (0.1)

0.915 (0.915)

0.831 (0.821)

-0.036

0.879

0.795

12j

PANI-4.5Fe-HT2

Fe/Fe3C/Fe1-xS

0.61 (0.102)

0.903 (0.903)

0.809 (0.809)

-0.042

0.861

0.767

12k

Fe-Mel-CPS

Fe/Fe3C/Fe3O4

0.5 (0.5)

0.902 (0.886)

0.832 (0.810)

0.017

0.886

0.816

12l

Fe/Co-Nx

0.1 (0.1)

0.895 (0.923)

0.772 (0.829)

-0.020

0.875

0.752

12m

Fe-P

0.0395 (0.0395)

0.794 (0.912)

0.492 (0.804)

-0.009

0.785

0.483

13a

Fe-Nx

0.0796 (0.904)

0.929 (0.904)

0.836 (0.768)

0.064

0.888

0.742

13b

No

0.6 (0.0326)

0.934 (0.934)

0.857 (0.830)

-0.078

0.856

0.779

13c

?

?

0.739

0.428

N/A

0.723

0.412

13d

Fe3(PO4)2

0.1 (0.14)

0.712 (0.928)

0.528 (0.851)

-0.021

0.691

0.507

13e

r-Fe2O3

0.1 (0.1)

0.907 (0.903)

0.846 (0.819)

0.000

0.907

0.846

this work

a-Fe2O3/CNT Fe3O4

O-NiCoFe LDH

Fe10@NOMC

Fe-PANI/C-Mela FP-Fe-TA-N OxBP-Fe Fe/N/G-0.3 Fe-N-Graphene

FeCoN Fe-P-900 Fe-N/C-800 FePhen@MOF-ArNH3 rGO-N-Fe FPO GF+N2+Fe1_800

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