Supplementary Information

Ternary Interfacial Superstructure Enabling Extraordinary

Hydrogen Evolution Electrocatalysis

Hongliang Jiang,1 Yunxiang Lin,1 Bingxu Chen,2 Youkui Zhang,1 Hengjie Liu,1 Xuezhi Duan,*2 De

Chen,3 and Li Song*1

1National Synchrotron Radiation Laboratory, CAS Center for Excellence in Nanoscience,

University of Science and Technology of China, Hefei, Anhui 230029, China.

2State Key Laboratory of Chemical Engineering, East China University of Science and

Technology, 130 Meilong Road, Shanghai, 200237, China.

3Department of Chemical Engineering, Norwegian University of Science and Technology, N-

7491 Trondheim, Norway.

*E-mail: song2012@ustc.edu.cn (L.S.); xzduan@ecust.edu.cn (X.Z.D.)

1

Fig. S1. Schematic diagram of ethylenediaminetetraacetic acid nickelous salt (EDTA-Ni).

2

Fig. S2. (a) XPS survey spectrum and (b) Ni 2p XPS spectrum of the EDTA-Ni. The Ni content in the

EDTA-Ni is 19.2 wt%.

3

Fig. S3. TEM images of (a, c) Ni/NiO@C-1 and (b, d) Ni/NiO@C-3.

4

Fig. S4. HRTEM image of Ni/NiO@C-2. The lattice fringe distances of 2.04, 1.78 and 2.41 Å coincided

well with the Ni(111), Ni(200) and NiO(111) facets.

5

Fig. S5. HRTEM image of Ni/NiO@C-2.

6

Fig. S6. TGA of the Ni/NiO@C-2 and Ni/NiO@C-2 acid treatment. From the amount of the

resultant solid (NiO), the calculated Ni content in the Ni/NiO@C-2 is 55.0 wt%.

7

Fig. S7. (a) C 1s and (b) O 1s XPS spectra of the Ni/NiO@C-2.

8

Fig. S8. The Raman spectrum of the Ni/NiO@C-2.

9

Fig. S9. Linear fitting spectra of the Ni/NiO@C-1 based the spectra of the measured Ni/NiO@C-1, the

Ni foil and the NiO foil.

10

Fig. S10. Linear fitting spectra of the Ni/NiO@C-3 based the spectra of the measured Ni/NiO@C-3, the

Ni foil and the NiO foil.

11

Fig. S11. EXAFS fitting curves of the Ni/NiO@C-1 and the Ni/NiO@C-3.

12

Fig. S12. Normalized Ni K-edge XANES spectra of the Ni/NiO@C-2 oxidation as well as the Ni foil and

NiO foil reference samples.

13

Fig. S13. Linear fitting spectra of the Ni/NiO@C-2 oxidation based the spectra of the measured

Ni/NiO@C-2 oxidation, the Ni foil and the NiO foil.

14

Fig. S14. EXAFS fitting curves of the Ni/NiO@C-1 and the Ni/NiO@C-2 oxidation.

15

Fig. S15. ECSA evaluation of the Ni/NiO@-C-2. Typical cyclic voltammetry curves with different scan

rates.

16

Fig. S16. ECSA evaluation of the Ni/NiO@-C and control samples. Typical cyclic voltammetry curves of

(a) Ni/NiO@-C-1, (b) Ni/NiO@-C-3, (c) Ni/NiO@-C-2 acid treatment and (d) Ni/NiO@-C-2 oxidation

with different scan rates.

17

Fig. S17. ECSA linear fitting. Current difference of all catalysts against different scan rates for the

estimation of double-layer capacitance, error bars means standard deviations from three

independent measurements.

18

Fig. S18. TEM images of the Ni/NiO@C-2 acid treatment.

19

Fig. S19. Temperature-dependent resistivity of the Ni/NiO@C-2.

20

Fig. S20. HER durability test in 1 M KOH and 1 M PBS. Chronopotentiometry curves at a constant

current density of 10 mA cm-2.

21

Fig. S21. XRD patterns of the Ni/NiO@C-2 after HER test.

22

Fig. S22. Ni K-edge XAFS k3(χ(k)) oscillation curves of the Ni/NiO@C-2 before and after HER test.

23

Fig. S23. HER performance of the Ni/NiO@C-2 catalyst loaded the carbon fibre paper. (Inset:

chronopotentiometry curves at a constant current density of 20 mA cm-2).

24

Fig. S24. Atomic configurations of the Ni (a) and NiO (b).

25

Fig. S25. Atomic configurations of water dissociation step at the Ni(111) surface with top view and

side view. Colour codes: Light blue represent Ni atoms in metal Ni. Red and white represent O and H

atoms.

26

Fig. S26. Atomic configurations of water dissociation step at the the Ni(111)-NiO interface with top

view and side view. Colour codes: Light blue represent Ni atoms in metal Ni. Red and white represent

O and H atoms.

27

Fig. S27. HER reaction pathway of on the Ni(100) surface. The insets are atomic configurations

of water dissociation step. No stable TS was found.

28

Table S1. The content ratio of Ni and NiO in all samples by linear fitting of standard patterns

(Ni foil and NiO foil).

29

Samples Ni mass ratio (%) NiO mass ratio (%)

Ni/NiO@C-1 78.7 21.3

Ni/NiO@C-2 90.2 9.8

Ni/NiO@C-3 94.8 5.2

Ni/NiO@C-2 oxidation 20.1 79.9

Table S2. Fitting results of Ni K-edge EXAFS data.a

Samples Bond CN R (Å) σ2 (10-3 Å2)

Ni/NiO@C-1Ni-Ni 8.8 2.48 7.4

Ni-O 1.3 2.03 7.9

Ni/NiO@C-2Ni-Ni 9.1 2.47 7.1

Ni-O 0.7 2.07 11.9

Ni/NiO@C-3Ni-Ni 9.2 2.48 6.4

Ni-O 0.2 2.04 7.5

NiO-foilNi-Ni 12.0 2.95 7.2

Ni-O 6.0 2.08 6.9

Ni-foil Ni-Ni 12.0 2.48 6.1

aThe lengths of Ni-O and Ni-Ni bonds and coordination numbers are extracted from the curve-fitting

for Ni K-edge EXAFS data. R, the lengths of Ni-O and Ni-Ni bonds; CN, the coordination numbers; σ2,

the Debye-Waller factor. Error bounds (accuracies) are estimated as CN, 5 %; R, 1 %; 2, 1 %.

30

Table S3. Comparisons of HER activity of the Ni/NiO@C-2 with some representative HER electrocatalysts recently reported in basic media.

CatalystHER

Overpotential for 10 mA cm-2 (mV)

Mass loading (mg cm-2)

Reference

Ni/NiO@C-2 64 0.27 This work

Ni-BDT-A 80 0.30 Chem 2017, 3, 122

Ni/NiO-CNT 80 0.28 Nat. Commun. 2014, 5, 695

Ni/NiO 120 0.59 Angew. Chem. Int. Ed. 2016, 55, 693

Co/CoO 120 0.12 J. Am. Chem. Soc. 2015, 137,2688

TiO2 NDs/Co NSNTs-CFs

108 0.75 Angew. Chem. Int. Ed. 2017, 56, 2960

Co-NRCNTs 370 0.28 Angew. Chem. Int. Ed. 2014, 53, 4372

Ni5P4 film 150 / Angew. Chem. Int. Ed. 2015, 54, 12361

c-CoSe2 200 0.50 Adv. Mater. 2016, 28, 7527

Ni-MoS2 98 0.89 Energ. Environ. Sci. 2016, 9, 2789

ZnCoS 85 0.29 J. Am. Chem. Soc. 2016, 138, 1359

NiCoS 88 0.30 Adv. Energ. Mater. 2015, 5, 1402031

CoMn-S@NiO 125 / ACS Catal. 2016, 6, 2797

31

Table S4. Comparisons of HER activity of the Ni/NiO@C-2 with some representative HER electrocatalysts recently reported in neutral media.

CatalystHER

Overpotential for 10 mA cm-2 (mV)

Mass loading (mg cm-2)

Reference

Ni/NiO@C-2 76 0.27 This work

N, P doped-graphene 610 0.20 ACS Nano 2014, 8, 5290

CoP3 concave polyhedrons

195 1.00 Phys. Chem. Chem. Phys. 2017, 19, 2104

SiO2/PPy NTs-CFs 183 0.34 Angew. Chem. Int. Ed. 2017, 56, 8120

N-Carbon coated P-W2C composite

185 3.50 J. Mater. Chem. A 2017, 5, 765

MoP2 nanosheet array 85 7.80 J. Mater. Chem. A 2016, 4, 7169.

CoP/CC 106 0.92 J. Am. Chem. Soc. 2014, 136, 7587

Co-HNP/CC 85 1.00 Angew. Chem. Int. Ed. 2016, 55, 6725

Ni-C-N nanosheets 90 0.20 J. Am. Chem. Soc. 2016, 138, 14546

FeP/CC 140 4.20 ACS Appl. Mater. Interfaces 2014, 6,

20579Co9S8 anosheets/CFs 175 0.40 J. Mater. Chem. A 2015,

4, 6860.Co-NRCNTs 540 0.28 Angew. Chem. Int. Ed.

2014, 53, 4372Co-S film 160 0.22 J. Am. Chem. Soc. 2013,

135, 17699

32

Table S5. Confirmation of constructed Ni model through comparing with reported results.

Method Cubic lattice constant (Å) Reference

Experiment 3.52 1

GGA-PBE 3.53 This work

1. C. Kittel, Introduction to Solid State Physics, 7th ed., John Willy and Sons Press, New York, 2005, p.

544.

Table S6. Confirmation of constructed NiO model through comparing with reported results.

Method Cubic lattice constant (Å) Magnetic

moment (μ)

Reference

GGA+U(6.3eV[1]) 4.17 1.81 This work

Experimental results 4.18 1.64-1.90 2

1. Bouzoubaa A, Costa D, Diawara B, et al. Corros. Sci., 2010, 52: 2643.

2. Bredow T, Gerson A R. Phys. Rev. B, 2000, 61: 5194.

In this work, the cubic lattice constant and magnetic moment of the constructed Ni model and NiO

model are according with previous reported results.

33

Table S7. Calculation results of kinetics energy barriers of Volmer (ΔG(H2O)) and Tafel steps (ΔG(H))

on different interfaces.

Surfaces ΔG(H2O) (eV) ΔG(H) (eV)

Ni(111) 0.87 -0.06

Ni(111)-NiO 0.68 0.11

34