S-1

Supporting Information

NiAg0.4 3D porous nanoclusters with epitaxial

interfaces exhibiting Pt like activity towards

hydrogen evolution in alkaline medium

Chidanand Hegde,‡a Xiaoli Sun,‡b Hao Ren,c Aijian Huang,d Daobin Liu,c Bing Li,e Raksha

Dangol,c Chuntai Liu,f Shuiqing Li,*b Hua Li*a and Qingyu Yan*c

aSingapore Center for 3D Printing, Department of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore

bDepartment of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China

cDepartment of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore

dSchool of Electronics Science and Engineering, University of Electronic Science and Technology of China, Chengdu, 610054, P.R. China

eInstitute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), 2 Fusionopolis Way Innovis #08-03, Singapore 138634, Singapore

fKey Laboratory of Materials Processing and Mold, Ministry of Education, Zhengzhou University, Zhengzhou 450002, China

*Corresponding authors.

E-mail addresses: alexyan@ntu.edu.sg (Q. Yan), lishuiqing@mail.tsinghua.edu.cn (S. Li), lihua@ntu.edu.sg (H. Li).

‡These authors contributed equally.

Electronic Supplementary Material (ESI) for Nanoscale.This journal is © The Royal Society of Chemistry 2020

S-2

30 40 50 60 70 80

Inte

nsity

(a.u

.) NiAg0.13 3DPNC

2(degree)

Ni

Ag

NiAg0.25 3DPNC

NiAg0.34 3DPNC

PDF #01-087-0720

NiAg0.4 3DPNCPDF #01-071-4654

30 40 50 60 70 80

NiAg0.44 3DPNC

NiAg0.6 3DPNC

PDF #01-087-0720)PDF #01-071-4654)

NiAg0.95 3DPNC

NiAg2.75 3DPNC

Ag

Inte

nsity

(a.u

.)

2(degree)

Ni

(a) (b)

Fig. S1 XRD patterns of (a) NiAg0.13 3DPNC, NiAg0.25 3DPNC, NiAg0.34 3DPNC, and NiAg0.4 3DPNC, and (b) NiAg0.44 3DPNC, NiAg0.6 3DPNC, NiAg0.95 3DPNC, and NiAg2.75 3DPNC.

1000 800 600 400 200 0

Ni 2p

Ag 3s

Ag 3pO 1s

Ag 3d

C 1s

Cou

nts

/s

Binding Energy (eV)

Ni 3p

Fig. S2 XPS survey spectrum of NiAg0.4 3DPNC.

S-3

100 nm 1 µm

(a) (b)

Fig. S3 FESEM images of (a) Ag NPs, (b) Ni 3DPNC.

S-4

Fig. S4 HRTEM image of (a) NiAg0.4 3DPNC, (b) FFT analyzed image of NiAg0.4 3DPNC, and (c) HRTEM image of Ag/Ni(OH)2.2/3H2O precursor.

S-5

(a)

(d)(c)

(b)

0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.02

0.00

0.02

0.04

0.06

0.08

45.3 mV dec-1

47.4 mV dec-1

46.5 mV dec-1

50.42 mV dec-1

Ove

rpot

entia

l (V)

log j

NiAg0.13 3DPNC

55.7 mV dec-1

NiAg0.25 3DPNC

NiAg0.4 3DPNC

NiAg0.34 3DPNC

NiAg0.44 3DPNC

0.0 0.2 0.4 0.6 0.8 1.0 1.2-0.02

0.00

0.02

0.04

0.06

0.08

0.10

0.12

O

verp

oten

tial (

V)

log j

NiAg0.6 3DPNC

91.5 mV dec-1

71.3 mV dec-1

46.4 mV dec-1

46.2 mV dec-1

NiAg0.95 3DPNC

NiAg4.42 3DPNC

NiAg2.75 3DPNC

-0.3 -0.2 -0.1 0.0-100

-80

-60

-40

-20

0

Cur

rent

Den

sity

(mA

cm-2)

Evs RHE (V)

NiAg0.13 3DPNC NiAg0.25 3DPNC NiAg0.34 3DPNC NiAg0.4 3DPNC NiAg0.44 3DPNC NiAg0.6 3DPNC NiAg0.95 3DPNC NiAg2.75 3DPNC NiAg4.42 3DPNC

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00

50

100

150

200

250

300

350

400

Ove

rpot

entia

l (m

V)

Mass loading (mg cm-2)

NiAg0.4 3DPNC Pt/C Ni 3DPNC Ag NPs

Fig. S5 (a) Variation of overpotential with catalyst loading for Ni 3DPNC, Ag NPs, NiAg0.4 3DPNC, and Pt/C catalysts. (b) HER polarization curves of NiAgx 3DPNC with varying Ni to Ag ratios without iR correction and their corresponding (c-d) Tafel plots.

S-6

6052 50 45

5161

69

110

140

0

25

50

75

100

125

150

NiAg0.25 NiAg0.34 NiAg0.4NiAg0.44

NiAg0.6 NiAg0.95 NiAg4.42NiAg2.75

Ove

rpot

entia

l (m

V)

CatalystNiAg0.13

(a) (b)

2840

132

280

0

50

100

150

200

250

300

Ag NPsNiAg0.4 3DPNC Ni 3DPNC

Catalyst

@10

mA

cm

-2 (m

V)

Pt/C

Fig. S6 Variation of overpotential at 10 mA cm-2 for (a) synthesized catalysts with varying Ag composition, (b) Pt/C, NiAg0.4 3DPNC, Ni 3DPNC and Ag NPs.

-0.4 -0.3 -0.2 -0.1 0.0

-120

-100

-80

-60

-40

-20

0

Cur

rent

Den

sity

(mA

cm-2)

Evs RHE (V)

NiAg0.4 3DPNC Pt/C

Fig. S7 HER polarization curves for NiAg0.4 3DPNC and Pt/C in 0.5 M H2SO4.

S-7

0.675 0.700 0.725 0.750 0.775

-0.4

-0.2

0.0

0.2

0.4

NiAg0.4

j (m

A cm

-2)

E vs RHE (V)

10 mV/s 20 mV/s 50 mV/s

40 mV/s 60 mV/s

30 mV/s

0.675 0.700 0.725 0.750 0.775-0.75

-0.50

-0.25

0.00

0.25

0.50

0.75

j (m

A cm

-2)

E vs RHE (V)

10 mV/s 20 mV/s 30 mV/s

50 mV/s

Ni

40 mV/s

0.675 0.700 0.725 0.750 0.775

-1.2

-0.8

-0.4

0.0

0.4

0.8

1.2

j (m

A cm

-2)

E vs RHE (V)

5 mV/s 10 mV/s 20 mV/s 50 mV/s

Ag

30 mV/s 40 mV/s

0.00 0.25 0.50 0.75 1.00 1.25

-10

-5

0

5

10

j (m

A cm

-2)

E vs RHE (V)

50 mV/s

(a)

(d)(c)

(b)

Fig. S8 Cyclic voltagram (CV) curves for (a) NiAg0.4 3DPNC, (b) Ni 3DPNC, (c) Ag NPs, and (d) CV curve for underpotential deposition for Pt/C 20% wt. catalyst.

S-8

S2S1 S3 Fo

rmin

g en

ergy

(eV

)

-2.73

-2.02

-2.72

S1S2S3

S1S2

S3S1

S2

S3

S1S2

S3

-1.80

-2.11 -2.12

S2S1 S3

Form

ing

ener

gy (

eV)

(e)

(d)(c)(b)(a)

(f)

Ni Ag

Fig. S9 The top and side view of crystal structures of: (a) pristine Ni (111) surface, (b) Ag/Ni (111) surface where the adsorption sites: top of Ni (S1), the Ni fcc sites (S2) and Ni hcp sites (S3); the top and side view of crystal structures of (c) pristine Ag (111) surface, (b) Ni/Ag (111) surface where the adsorption sites: top of Ag (S1), the Ag fcc sites (S2) and Ag hcp sites (S3); (e) the forming energy of Ag adsorbed on Ni (111) surface; (f) the forming energy of Ni adsorbed on Ag(111) surface.

S-9

0.4 0.6 0.8 1.0 1.2 1.4 1.60.00

0.02

0.04

0.06

Ove

rpot

entia

l (V)

Log j

Equation y = a + b*x

Weight No Weighting

Residual Sum of Squares

1.21983E-6

Pearson's r 0.99965Adj. R-Square 0.99915

Value Standard Erro

OverpotentialIntercept -0.06192 0.00112Slope 0.07785 9.24844E-4

Fig. S10 Tafel plot of NiAg0.4 3DPNC to evaluate the exchange current density. Exchange current density was computed from the Tafel equation.

The exchange current density of the NiAg0.4 3DPNC based on the geometric surface area was computed from the Tafel equation as shown below:

η = -0.062 + 0.077 log j

0 = -0.062 + 0.077 log j

Log j = 0.8052

j0geometric = 6.3856 mA cm-2geometric

j0 (ECSA) = 6.3856/125 mA cm-2(ECSA)

j0 (ECSA) = 5.10 * 10-5 A cm-2(ECSA)

S-10

-0.3 -0.2 -0.1 0.0-100

-80

-60

-40

-20

0

Cur

rent

Den

sity

(mA

cm

-2)

Evs RHE (V)

NiAg0.4 3DPNC before stability test NiAg0.4 3DPNC post stability test

Fig. S11 Comparison of HER polarization curve of NiAg0.4 3DPNC after 80 hours chronoamperometry test with the initial catalyst.

S-11

20 30 40 50 60 70 80

Ag (PDF # 01-087-0720)

In

tens

ity (a

.u.)

2 Theta (degree)

carbon cloth

Ni (PDF # 01-071-4654) (b)(a)

(d)(c)

880 875 870 865 860 855 850 845

Cou

nts

/s

Binding Energy (eV)

sat.Ni2+ 2p1/2

Ni 2p1/2

sat. Ni2+ 2p3/2

Ni 2p3/2

378 376 374 372 370 368 366 364 362

Cou

nts

/s

Binding Energy (eV)

Ag 3d5/2

Ag 3d3/2

Fig. S12 (a) XRD pattern of NiAg0.4 3DPNC after 80 hours chronoamperometry test. (b) FESEM image of the NiAg0.4 3DPNC after chronoamperometry test. XPS spectra of NiAg0.4 3DPNC after 80 hours chronoamperometry test in the (c) Ni 2p region, (d) Ag 3d region.

S-12

Table S1. Inductive couple plasma- atomic emission spectroscopy results for the synthesized samples with different Ni/Ag ratios.

Ni : Ag ratio in the precursor solution

Expected molar

concentration from synthesis

Measured molar

concentration from ICP-

OES

Expected molar

concentration from

synthesis

Measured molar

concentration from ICP-

OES

Sample name in the report

Ni (%) Ni (%) Ag (%) Ag (%)

1 : 0.1 90.9 88.43019 9.1 11.56981 NiAg0.13 3DPNC

1 : 0.2 83 80.20356 17 19.79644 NiAg0.25 3DPNC

1 : 0.3 76.9 74.63433 23.1 25.36567 NiAg0.34 3DPNC

1 : 0.4 71.5 71.89 28.5 28.11 NiAg0.4 3DPNC

1 : 0.5 66.67 69.57572 33.33 30.42428 NiAg0.44 3DPNC

1 : 0.6 62.5 62.55256 37.5 37.44744 NiAg0.6 3DPNC

1 : 0.8 55.55 51.37111 44.45 48.62889 NiAg0.95 3DPNC

1 : 2 33.33 26.63245 66.67 73.36755 NiAg2.75 3DPNC

1 : 3 25 18.4579 75 81.5421 NiAg4.42 3DPNC

68.5 31.5

NiAg0.4 3DPNC Post chronoamperometr

y test

Table S2. Roughness factor values for different catalysts which was evaluated from the double layer capacitance.

Catalyst Cdl (mF cm-2 ) Roughness factor (cm2 per cm2

(geometric))

Ni 3DPNC 7 175

Ag NPs 12.8 320

Pt/C 20.4738 mC cm-2

97.5

NiAg0.4 3DPNC 4.9 125

S-13

Table S3. HER activity of the NiAg0.4 3DPNC in comparison with other recently reported catalysts with good activity.

Catalyst HER

overpotential

(mV@mA

cm-2)

Tafel

slope

(mV

dec-1)

Electrolyte Stability Reference

Boron doped

RhFe alloy

25 mV @ 10

mA cm-2

32 0.5 M H2SO4 8 hours 1

Ni20Fe20Mo10Co

35Cr15 high

entropy alloy

172 mV @ 10

mA cm-2

41 1 M KOH 8 hours 2

Pt3Ni3 NWs 70 mV @

19.8 mA cm-2

NA 1 M KOH 3 hours 3

Micro-nano

MoS2 spheres

214 mV @ 10

mA cm-2

74 0.5 M H2SO4 24 hours 4

Pt3Co

nanoparticles

32.6 mV @

10 mA cm-2

28.6 0.5 M H2SO4 5000

CV

cycles

5

np-CoP3 on Ti

mesh

76 mV @ 10

mA cm-2

50 1 M KOH 60 hours 6

PtCo–Co/TiM 70 mV @

46.5 mA cm-2

35 1 M KOH 50 hours 7

Fe1.89Mo4.11O7/

MoO2

197 mV @10

mA cm-2

79 1 M KOH 1000

CV

cycles

8

V-doped Ni3S2

Nanowires on Ni

foam

68 mV @ 10

mA cm-2

112 1 M KOH 7000

cycles

9

S-14

CrOx/Ni–Cu 48 mV @ 10

mA cm-2

64 KH2PO4 +

K2HPO4

buffer (pH =

7)

24 hours 10

FeP

nanoparticles

154 mV @ 10

mA cm-2

65 0.5 M H2SO4 1.66

hours

11

IrAg nanotubes 20 mV @ 10

mA cm-2

61.1 0.5 M H2SO4 6 hours 12

NiAg0.4 3DPNC 40 mV @ 10

mA cm-2

39.1 1 M KOH 80

hours

and

5000

CV

cycles

This work

S-15

References

1 L. Zhang, J. Lu, S. Yin, L. Luo, S. Jing, A. Brouzgou, J. Chen, P. K. Shen and P. Tsiakaras, App. Catal. B: Envir., 2018, 230, 58-64.

2 G. Zhang, K. Ming, J. Kang, Q. Huang, Z. Zhang, X. Zheng and X. Bi, Electrochim. Acta, 2018, 279, 19-23.

3 P. Wang, K. Jiang, G. Wang, J. Yao and X. Huang, Angew. Chem., 2016, 55, 12859-12863.

4 B. Guo, K. Yu, H. Li, H. Song, Y. Zhang, X. Lei, H. Fu, Y. Tan and Z. Zhu, ACS App. Mater. Interfaces, 2016, 8, 5517-5525.

5 Z. Cheng, X. Geng, L. Chen, C. Zhang, H. Huang, S. Tang and Y. Du, J. Mater. Sci., 2018, 53, 12399-12406.

6 Y. Ji, L. Yang, X. Ren, G. Cui, X. Xiong and X. Sun, ACS Sustain. Chem. Eng., 2018, 6, 11186-11189.

7 Z. Wang, X. Ren, Y. Luo, L. Wang, G. Cui, F. Xie, H. Wang, Y. Xie and X. Sun, Nanoscale, 2018, 10, 12302-12307.

8 Z. Hao, S. Yang, J. Niu, Z. Fang, L. Liu, Q. Dong, S. Song and Y. Zhao, Chem. Sci., 2018, 9, 5640-5645.

9 Y. Qu, M. Yang, J. Chai, Z. Tang, M. Shao, C. T. Kwok, M. Yang, Z. Wang, D. Chua, S. Wang, Z. Lu and H. Pan, ACS Appl. Mater. Interfaces, 2017, 9, 5959-5967.

10 C.-T. Dinh, A. Jain, F. P. G. de Arquer, P. De Luna, J. Li, N. Wang, X. Zheng, J. Cai, B. Z. Gregory, O. Voznyy, B. Zhang, M. Liu, D. Sinton, E. J. Crumlin and E. H. Sargent, Nat. Energy, 2018, 4, 107-114.

11 L. Tian, X. Yan and X. Chen, ACS Catal., 2016, 6, 5441-5448.12 M. Zhu, Q. Shao, Y. Qian and X. Huang, Nano Energy, 2019, 56, 330-337.