Supporting Information

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Supporting Information

Boosted Oxygen Evolution Reactivity via Atomically

Iron Doping in Cobalt Carbonate Hydroxide Hydrate

Shan Zhang

†£#

_{, Bolong Huang}

δ

_{, Liguang Wang}

§

_{, Xiaoyan Zhang}

†#

_{, Haishuang Zhu}

†£

_{, Xiaoqing Zhu}

†

£

_{, Jing Li}

†£*

_{, Shaojun Guo}

#

_{and Erkang Wang}

†£

†

_{State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry,}

Chinese Academy of Sciences, Changchun, Jilin, 130022, China.

£

_{University of Science and Technology of China, Hefei, Anhui, 230029, China.}

#

_{Department of Materials Science & Engineering, College of Engineering, Peking University,}

Beijing, 100871, China.

δ

_{Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University,}

Hung Hom, Kowloon, Hong Kong SAR, China

§

_{Department of Physics, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong,}

China.

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Figures

40.0 μm

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Figure S2. XRD profiles of the original CCHH/NF and after electrolysis treatment for different time. The black

line marked with star represents the standard pattern of CCHH (JCPDS: 48-0083). While the green line with triangle stands for Ni profile (JCPDS: 65-0380). Since the powder for XRD analysis was detached from substrate NF by sonication, and small amount of NF would probably also peeled off, thus contributing to the appearance of peak at around 45°. Fe-CCHH/NF-30 Fe-CCHH/NF-10 In te n s it y ( a .u .) Degree (2) CCHH/NF Fe-CCHH/NF-60 10 20 30 40 50 60

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Figure S3. FT-IR spectra of CCHH/NF and Fe-CCHH/NF-30.

Considering the similar diffraction pattern between CCHH and cobalt oxyhydroxide, FT-IR spectrum of CCHH/NF was carried out to confirm its chemical identity (Figure S3). The existence of CO32- was supported by

the vibration bands at 1500, 1072, 831, 748 and 687 cm-1_{, which could be attributed to the stretching vibration}

ν(OCO2), ν(C=O), δ(CO3), δ(OCO), and ρ(OCO), respectively.1 The small shoulder band at 1381 cm-1

demonstrated that the CO32- might be also existed in form of intercalated carbonates, just like that of layered double

hydroxide.2, 3_{In addition, the strong peak at 3500 cm}-1_{was the characteristic stretching vibration for O-H group.}4

These observations suggested that the as-prepared product is exactly CCHH, rather than cobalt oxyhydroxide. In addition, the Fe-CCHN/NF-30 exhibits almost the same FT-IR spectrum as that for CCHH/NF, which is another piece of evidence for the unchanged composition. Specifically, the absence of peaks that can be assigned to Co-O bond5_{and Fe-O bond}6, 7_{illustrates that neither CoO}

x nor FeOx exist in the final material.

3600 3000 2400 1800 1200 600 20 40 60 80 100 1072 1380 1500 3500 830 750 687 T ra n s m it ta n c e ( % ) Wavenumber (cm-1) CCHH/NF Fe-CCHH/NF-30 518

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5 μm

a

b

Figure S4. SEM images of (a) Fe-CCHH/NF-10 and (b) Fe-CCHH/NF-60.

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5 nm

50 nm

a

b

5 nm

0.22 nm

c

d

Figure S5. TEM images of (a) Fe-CCHH/NF-10 and (b) Fe-CCHH/NF-60. The corresponding HRTEM images of

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7 / 28 805 800 795 790 785 780 775 In te n s it y ( a .u .)

Binding Energy (eV)

781.2 eV Co 2p1/2 Co 2p3/2 805 800 795 790 785 780 775 781.3 eV Co 2p_1/2 Co 2p3/2 In te n s it y ( a .u .)

a

b

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8 / 28 7050 7200 7350 7500 7650 0.0 0.3 0.6 0.9 1.2 1.5 A b s o rp ti o n ( a .u .) Energy (eV) Fe foil Fe₂O₃ Fe-CCHH/NF-30 7650 7800 7950 8100 8250 0.0 0.3 0.6 0.9 1.2 1.5 1.8 A b s o rp ti o n ( a .u .) Energy (eV) Co foil CoO CCHH/NF Fe-CCHH/NF-30

a

b

Figure S7. XAS of (a) Co k-edge for Co foil, CoO, CCHH/NF and Fe-CCHH/NF-30 and (b) Fe k-edge for Fe foil,

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Figure S8. Experimental Fourier transform magnitude (EFT, dots), and the corresponding fits of EXAFS (red line)

profile for the obtained Fe-CCHH/NF-30.

0 1 2 3 4 5 0.0 0.3 0.6 0.9 1.2 1.5 _EFT Fit F T l (R )l ( Å -4 ) R (Å)

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Figure S9. The polarization curves of various catalysts without iR-corrected.

1.2 1.3 1.4 1.5 1.6 1.7 0 40 80 120 160 200 240 280 j (m A /c m 2 ) E (V vs.RHE) NF CCHH/NF Fe-CCHH/NF-10 Fe-CCHH/NF-30 Fe-CCHH/NF-60

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a

b

c

5 µm

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10 nm

a

b

0.22 nm Co Fe Co + Fe

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13 / 28 1.2 1.3 1.4 1.5 1.6 1.7 0 100 200 300 400 j (m A /c m 2 ) E (V vs.RHE) CFP CCHH/CFP Fe-CCHH/CFP-30 0.3 0.6 0.9 1.2 1.5 1.8 2.1 0.24 0.27 0.30 0.33 0.36 70 mV/d ec CCHH/CFP Fe-CCHH/CFP-30 O v e rp o te n ti a l (V v s .R H E ) Log[j(mA/cm2_)] 53 mV/d ec

a

b

c

270 300 330 360 Fe-CCHH/CFP-30 10 ( m V v s .R H E ) CCHH/CFP

Figure S12. (a) LSV curves of CFP, CCHH/CFP and Fe-CCHH/CFP-30; (b) The histogram of the overpotential

that needed for CCHH/CFP and Fe-CCHH/CFP-30 to reach the current density of 10 mA/cm2_{and (c) the}

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Figure S13. OER activity of Fe-CCHH/NF-30 and RuO2@NF with the same mass loading.

1.20 1.28 1.36 1.44 1.52 1.60 0 40 80 120 160 200 240 j (m A /c m 2 ) E (V vs.RHE) RuO₂@NF Fe-CCHH/NF-30

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5 μm

20 μm

a

_b

Figure S14. SEM images of (a) CCHH obtained by the similar hydrothermal method without the presence of the

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Figure S15. The polarization curves of CHHH@NF, Fe-CCHH@NF-30 and Fe-CCHH/NF-30.

1.20 1.26 1.32 1.38 1.44 1.50 1.56 0 40 80 120 160 200 240 j (m A /c m 2 ) E (V vs.RHE) CCHH@NF Fe-CCHH@NF-30 Fe-CCHH/NF-30

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17 / 28 5 µm 1.2 1.3 1.4 1.5 1.6 1.7 0 30 60 90 120 150 j (m A /c m 2 ) E (V vs.RHE) Fe-NF-30 Fe-CCHH/NF-30

a

b

Figure S16. (a) SEM image of Fe-NF-30; (b) The LSV curves of Fe-CCHH/NF-30 and Fe-NF-30 without the iR

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Figure S17. The histogram of TOF values for CCHH/NF and Fe-CCHH/NF-30 at the overpotential of 280 mV (vs.

RHE). 0.000 0.015 0.030 0.045 0.060 Fe-CCHH/NF-30 T O F ( s -1 ) CCHH/NF x 21

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19 / 28 0.86 0.88 0.90 0.92 0.94 0.96 0.98 -0.2 -0.1 0.0 0.1 0.2 0.3 j (m A /c m 2) E (V vs.RHE) 80~200 mV/s 0.86 0.88 0.90 0.92 0.94 0.96 0.98 -1.0 -0.5 0.0 0.5 1.0 j (m A /c m 2 ) E (V vs.RHE) 80~200 mV/s 0.86 0.88 0.90 0.92 0.94 0.96 0.98 -1.6 -0.8 0.0 0.8 1.6 2.4 3.2 j (m A /c m 2 ) E (V vs.RHE) 80~200 mV/s 0.86 0.88 0.90 0.92 0.94 0.96 0.98 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 j (m A /c m 2) E (V vs.RHE) 80~200 mV/s 0.86 0.88 0.90 0.92 0.94 0.96 0.98 -1.0 -0.5 0.0 0.5 1.0 1.5 j (m A /c m 2 ) E (V vs.RHE) 80~200 mV/s

a

b

c

d

e

f

80 100 120 140 160 180 200 0.5 1.0 1.5 2.0 2.5 3.0 3.5 NF 1.5 mF/cm2 CCHH/NF 5.2 mF/cm2 Fe-CCHH/NF-10 5.3 mF/cm2 Fe-CCHH/NF-30 4.5 mF/cm2 Fe-CCHH/NF-60 3.0 mF/cm2  j0.9 1 5 V (m A /c m 2 ) Scan rate (mV/s)

Figure S18. CV curves at different scan rates of (a) NF, (b) CCHH/NF, (c) Fe-CCHH/NF-10, (d) Fe-CCHH/NF-30

and (e) Fe-CCHH/NF-60 in potential window where no Faradaic processes occurred. (f) The plot of ΔJ (ΔJ = Ja -

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Figure S19. The Faradaic efficiency of Fe-CCHH/NF-30 for OER in 1 M KOH.

Calculated 24 32 40 48 56 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Measured n ( O2 ) /m m o l Time (min)

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10 µm

Figure S20. SEM image of Fe-CCHH/NF-30 after the stability test at the current density of about 55 mA/cm2_for

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Figure S21. The XRD pattern of Fe-CCHH-30 after the stability test.

8 16 24 32 40 48 56 64 In te n s it y ( a .u .) Degree (2) JCPDS: 48-0083

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24 / 28 538 536 534 532 530 528 After In te n s it y ( a .u .)

O 1s Before

a

b

740 735 730 725 720 715 710 705 In te n s it y ( a .u .)

Before

After Fe 2p1/2 Fe 2p3/2

Figure S23. XPS profiles of (a) Fe 2p and (b) O 1s for Fe-CCHH/NF-30 before and after the long time stability test

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Table S1. The weight ratio of Fe in Fe-CCHH/NF-t determined by ICP-AES. Element/

wt.% Fe-CCHH/NF-10 Fe-CCHH/NF-30 Fe-CCHH/NF-60

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Table S2. Structural parameters of Fe-CCHH/NF-30 obtained by fitting the FT EXAFS data. There are path

distance (R), the average coordination number (N), Debye-Waller factor (σ2_{), threshold energy correction (∆E), and}

the R-Factor of the fitting. The amplitude reduction factor (S02) is used as 0.75.

Shells R (Å) N σ2_(Å2₎ _{∆E (eV)} _R-Factor

Fe-O 1.99 ± 0.01 4.9 ± 0.7 0.009 ± 0.002 4.0 ± 1.6

Fe-Fe 3.06 ± 0.02 0.8 ± 0.4 0.010 ± 0.005 4.0±1.6

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Table S3. The OER catalytic data of Fe-CCHH/NF-30 and other previously reported CCHH-based or Co-based

catalysts in 1 M KOH.

Catalysts OER performance (j/mA cm-2_{@ η/mV)} Tafel Slope (mV dec-1₎ Durability (j/mA cm-2 @ T/h) Reference Fe-CCHH/NF-30 10@200 50@230 100@252 50 55@130 This work

t-CoII_CoIII _10@240 ₇₉ _~13@50 Angew. Chem. Int.

Ed., 2018, 57, 1241

Co1Mn1CH/NF

50@322

100@349 N.A. 50@18

J. Am. Chem. Soc., 2017, 139(24), 8320 Cu(OH)2@CCHH NW/CF 50@270 100@290 78 ~50@20 Small, 2017, 13, 1602755 Co3O4/Fe0.33Co0.66P NWs 50@215 59 30@150 100@150 Adv. Mater., 2018, 30, 1803551 Fe0.33Co0.67OOH PNSAs/CFC 10@266 30 10@24

Angew. Chem. Int. Ed., 2018, 57, 2672 Core-Shell NiFeCu 10@180 33 10@20 20@20 Nat. Commun., 2018, 9, 381 CoO/hi-Mn3O4 10@378 61 [email protected]

Angew. Chem. Int. Ed., 2017, 56, 8539 Co(OH)2-TCNQ/CF 25@276 50@315 101 35@25 Adv. Mater. 2018, 30, 1705366

O-NiFe LDH 10@184 29 N.A. Energy Environ.

Sci., 2019, 12, 572

CoFeNiOx/NF

10@240

100@272 32 N.A.

J. Am. Chem. Soc. 2016, 138, 8946

F-CoOOH/NF 10@270 54 30@10 Angew. Chem. Int.

Ed., 2018, 57, 15471 NixFe1-xSe2-DO 10@195 250@262 28 10@24 Nat. Commun., 2016, 7, 12324 H2O-Plasma Exfoliated LDHs /NF 10@232 36 20@12 Adv. Mater., 2017, 29, 1701546 CoSn2/NF 10@230 N.A. 10@14

Angew. Chem. Int. Ed., 2018, 57, 15237 NiFe2O4 /NiFe LDH 100@213 28 80@20 200@20 500@20

ACS Appl. Mater. Interfaces, 2018, 10, 26283 amorphous cobalt phyllosilicate 10@367 60 10@24 Adv. Mater., 2017, 29, 1606893

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