Chem, Volume 3

Supplemental Information

In Situ Electrochemical Production

of Ultrathin Nickel Nanosheets

for Hydrogen Evolution Electrocatalysis

Chengyi Hu, Qiuyu Ma, Sung-Fu Hung, Zhe-Ning Chen, Daohui Ou, Bin Ren, Hao MingChen, Gang Fu, and Nanfeng Zheng

S1

Figure S1. Structural characterization of -Ni(OH)2. (a, b) SEM, (c) TEM images and (d) XRD

pattern of -Ni(OH)2 grown on carbon cloth.

20 40 60 80

Ni-BDTInte

nsity (

a.u

.)

2 (degree)

Figure S2. XRD pattern of the as-prepared Ni-BDT (the two broad peaks come from carbon cloth).

S2

Figure S3. Experimental and simulated Raman spectra of Ni-BDT. (Inset: model used for

simulation) The peak assignment was shown in Table S1.

12001000 800 600 400 200 0

Inte

nsity (

a.u

.)

Binding Energy (eV)

Ni-BDT

S 2

p

S 2

s

Ni 3

p

C 1

s

O 1

s

Ni L

MM

Ni 2

p3

/2

Figure S4. XPS survey spectrum of Ni-BDT.

S3

Figure S5. (a) Cyclic voltammetry curves of Ni(OH)2, Ni-BDT and Ni-BDT-A in the region of 0.1-

0.2 V vs. RHE. The differences in current density variation (J=Ja-Jc) at an overpotential of 0.15 V

plotted against scan rate fitted to a linear regression enables the estimation of Cdl.

Figure S6. (a-c) SEM images at 0h, 1h and 12h of the activation process of Ni-BDT. (d) EDS spectra

of the catalysts in (a-c).

S4

Figure S7. (a) Thickness distribution of Ni-BDT-A from TEM. (b) HAADF-STEM image and EDS

elemental mapping images of Ni-BDT-A. (c) HRTEM image of Ni-BDT-A.

Figure S8. (a) AFM image, (b) corresponding height profile and (c) thickness distribution of Ni-

BDT. (d) AFM image, (e) corresponding height profile and (f) thickness distribution of Ni-BDT-A.

S5

200 400 600 800 1000 1200

Norm

aliz

ed Inte

nsity

Raman Shift / cm-1

Ni-BDT

Ni-BDT-A

Figure S9. Raman spectra of Ni-BDT and Ni-BDT-A.

Figure S10. (a) XPS survey spectra, (b) Ni 2p region, (c) S 2p region and (d) fitting results of S 2p

region of Ni-BDT and Ni-BDT-A.

S6

Figure S11. Electrochemical in-situ XAS of Ni-BDT. (a) Ni K-edge XANES, (b) k-space, and (c)

Fourier transformed R-space of Ni-BDT during HER activation. The cathodic current was set as 50

mA cm-2 during the activation. The in-situ XAS measurement was performed at 0.5h, 1h and 1.5h

at the voltage of -1 V to keep the situation of reduction and to avoid the disturbance of bubbles that

interfered the measurement.

Figure S12. Experimental and simulated XAFS spectra of Ni-BDT and Ni-BDT-A catalysts at the

Ni K-edge. The χ(k) data weighted by k3 and Fourier transformed (FT) to R-space (the k-space

ranging from 3 to 10.5 Å−1) to isolate the EXAFS contributions from each coordination shell. The

quantified fitting results are shown in Table S2.

S7

Figure S13. (a) EXAFS spectra and (b) HER performance of Ni-BDT-A catalysts after exposing to

air at room temperature for different time. The catalysts were easily oxidized by air to form Ni(OH)2

due to the ultrathin structure, resulting in the decrease of HER activity.

5 10 15 20 25 30

0.00

0.02

0.04

0.06

0.08

0.10

0.12

1.5 mF cm-2

1.1 mF cm-2

j (m

A c

m-2)

Ni(OH)2

Ni-BDT-A air 24h

Scan Rate (mV/s)

Figure S14. Double-layer capacitance of pristine Ni(OH)2 and Ni-BDT-A derived Ni(OH)2 (air

oxidation for 24h).

S8

Figure S15. (a) SEM image and (b) EDS spectrum of Ni-BDT-A soaked in 0.1 mM Zn(NO3)2

solution for 30 s and then washed by deionized water. (c) HER activity of Ni-BDT-A before and

after soaking in 0.1 mM Zn(NO3)2 solution and H2O for 30 s with the protection of N2.

Figure S16. (a) HER activity of Ni-BDT-A and (b) Ni foam in 1 M KOH and tetramethylammonium

hydroxide (TMAOH) electrolyte.

-0.3 -0.2 -0.1 0.0

-100

-80

-60

-40

-20

0

j (m

A c

m-2)

E (V vs. RHE)

Ni foam

Ni foam Na2S 10s

Ni foam Na2S 40s

Ni foam Na2S 100s

E (V vs. RHE)

Figure S17. HER activity of Ni foam before and after soaking in 1 mM Na2S aqueous solution for

different time at open circuit potential.

S9

Figure S18. SEM images and EDS of Ni thiolate synthesized by using 1,2-benzenedithiol as

ligand (a, c) before and (b, d) after electrochemical activation.

Figure S19. SEM images and EDS of Ni thiolate synthesized by using 1,3-benzenedithiol as

ligand (a, c) before and (b, d) after electrochemical activation.

S10

Figure S20. HER polarization curves of (a) Ni-12BDT and (b) Ni-13BDT before and after

activation.

Figure S21. (a) LSV plots of Ni(OH)2 and Ni-BDT-A in 1 M KOH electrolyte with and without

0.33 M urea. (b) Optical image of urea electrolysis device. (c) LSV plots of urea electrolysis using

Ni(OH)2 or Ni-BDT-A as both HER and UOR catalysts in 1 M KOH and 0.33 M urea. (d)

Chonopotentiometry of urea electrolysis using Ni-BDT-A as both HER and UOR catalyst at a

constant current density of 20 mA cm-2 (without iR compensation). All polarization curves were iR

corrected.

S11

Figure S22. SEM images of (a, b) NiFe-BDT and (c, d) NiFe-BDT-A. EDS of (e) NiFe-BDT and

(f) NiFe-BDT-A.

Figure S23. Polarization curves for (a) HER and (b) OER of NiFe-BDT before and after activation.

S12

Table S1. Theoretical frequencies of selected fundamental vibrational bands of Ni-BDT within the

frequency range of 100-1000 cm-1.

Peak position (cm-1) Assignment

170 m Ni-S

227 w Ni-SC-S

303 m Ni-SC-S

344 s Ni-S + ring

544 w C-S Ni-S

753 m C-S + ring

768 m C-S + ring

Abbreviation: , stretching; , in-plane ring deformation; β, in-plane bending

Relative intensity: s (strong); m (medium); w (weak)

Table S2. EXAFS fitting parameters of Ni-BDT and Ni-BDT-A.

Sample Shell CN R / Å Δσ2 / x10-3Å2 ΔE0 / eV

Ni foil

Ni-BDT

Ni-Ni

Ni-S

12

3.6±0.2

2.480±0.001

2.199±0.004

6.2±0.3

2.8±0.7

2.5±0.2

-0.8±0.6

Ni-BDT-A Ni-S 1.3±0.2 2.201±0.004 4.9±0.2 -7.9±1.4

Ni-Ni 4.9±0.8 2.476±0.009 8.5±0.1 -7.9±1.4

CN, coordination number; R, bonding distance; Δσ2, Debey-Waller factor; ΔE0, inner potential shift,

amplitude reduction factor S02 was set as 0.8 for all the samples.

Table S3. Comparison of the electrocatalytic HER performance of Ni-BDT-A with 2D metal organic

polymers reported recently.

Catalyst Electrode Loading

(mg cm-2)

Electrolyte (mV)@

10 mA cm-2

(mV)@

100 mA cm-2

Tafel slop

(mV/dec)

Reference

Ni-BDT-A CC 0.3 1M KOH 80 150 70 This work

Co-BHT GC 0.7×10−6

molCo cm-2

H2SO4 pH 1.3 ~340 — 149 [29]

Co-THT GC 1.1×10−6

molCo cm-2

H2SO4 pH 1.3 ~520 — 189

Co-BTT GC 5.5×10−7

molCo cm-2

H2SO4 pH 1.3 ~550 — — [30]

Ni-THT GC — 0.5M H2SO4 333 — 80.5 [31]

GC — 0.05M KOH ~570 — —

S13

Table S4. Comparison of the electrocatalytic HER performance of Ni-BDT-A with metal sulfide

electrocatalysts in alkaline electrolyte reported recently.

Catalyst Electrode Loading

(mg cm-2)

Electrolyte (mV)@

10 mA cm-2

(mV)@

100 mA cm-2

Tafel slop

(mV/dec)

Reference

Ni-BDT-A CC 0.3 1M KOH 80 150 70 This work

Ni3S2 Ni foam 1.6 1M KOH 223 — — [48]

NiCo2S4 Ni foam — 1M KOH ~85 240 84.5 [49]

CoMn-S@NiO CC — 1M KOH ~125 232 147.3 [50]

NiS Ni foam 1 1M KOH ~90 — 139 [51]

Ni3S2 Ni foam — 1M KOH 182 — 89 [52]

MoS2/Ni3S2 Ni foam 9.7 1M KOH 110 — 83 [53]

Ni-MoS2 CC 0.89 1M KOH 98 — 60 [54]

MoSx FTO 0.02 1M KOH 310 — 84 [55]

Ni foam — 1M KOH 210 335 —

ZnCoS GCE 0.285 1M KOH 85 136 — [56]

NiCoS Ti foil 0.3 1M KOH 88 240 118 [57]

Table S5. Comparison of the electrocatalytic HER performance of Ni-BDT-A with metal/metal

oxide electrocatalysts in alkaline electrolyte reported recently.

Catalyst Electrode Loading

(mg cm-2)

Electrolyte (mV)@

10 mA cm-2

(mV)@

100 mA cm-2

Tafel slop

(mV/dec)

Reference

Ni-BDT-A CC 0.3 1M KOH 80 150 70 This work

Ni/NiO-CNT GC 0.28 1M KOH 80 — 82 [13]

Ni foam 8 1M KOH — 95 —

Ni/NiO-Cr2O3 Ni foam 8 1M KOH — 150 (no ir) — [14]

Ni foam 24 1M KOH — 115 (no ir) —

Ni/NiO Ni foam 0.59 0.1M KOH ~120 ~260 114 [15]

Ni-Mo Ti foil 1 1M NaOH 80 — — [12]

2-cycle NiFeOx CFP 1.6 1M KOH — 220 — [58]

Co/CoO GC 0.12 1M KOH 232 — — [59]

Ni foam 2.1 1M KOH — ~210 —