Supporting Information for
Porous Two-Dimensional Nanosheets Converted from Layered Double
Hydroxides and Their Applications in Electrocatalytic Water Splitting
Hanfeng Liang,†,‡ Linsen Li,† Fei Meng,† Lianna Dang,† Junqiao Zhuo, †,# Audrey Forticaux,†
Zhoucheng Wang,‡,* and Song Jin†,*
†
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison,
Wisconsin 53706, United States and ‡College of Chemistry and Chemical Engineering, Xiamen
University, Xiamen 361005, China; #Institute of Analytical Chemistry, College of Chemical and
Molecular Engineering, Peking University, Beijing 100871, China.
Email: [email protected] (S.J.) and [email protected] (Z.W.)
Supporting Figures and Tables
Figure S1. Schematic illustration of the layered crystal structures of (A) NiGa layered double hydroxide
(LDH) and (B) β-Ni(OH)2 (side-view) and the conversion process from NiGa LDH to β-Ni(OH)2. Step
I: the Ga3+ ions in NiGa LDH layers react with OH- under hydrothermal conditions and form soluble
S1
Ga[(OH)4]-, resulting in the formation of porous β-Ni(OH)2 layers; Step II: as the Ga3+ ions dissolve, the
host layers are no longer positively charged, therefore, the charge-balancing anions will diffuse outward
from between the layers, resulting in the transition from NiGa LDH to porous β-Ni(OH)2. After
conversion, the basal d spacing (calculated from the PXRD) of the layered structures decreases from 7.8
Å (NiGa LDH nanoplates) to 4.6 Å [β-Ni(OH)2 porous nanosheets].
Figure S2. Low-magnification SEM images of as-grown (A) NiGa LDH nanoplates, (B) as-converted
porous β-Ni(OH)2 nanosheets, and (C) β-Ni(OH)2 microplates on carbon paper.
Table S1. Summary of the electrochemical properties of porous β-Ni(OH)2 nanosheets and β-Ni(OH)2
microplates.
Catalyst
η @ 10 mA cm-2
(mV vs. RHE)
Tafel slope
(mV dec-1)
j0,geometric
(mA cm-2)
Cdl (μF cm-2)
Relative
surface area
j0,normalized
(mA cm-2)
porous β-Ni(OH)2
nanoplates
415
68.1
0.317
107.3
3.94
0.081
β-Ni(OH)2 microplates
541
60.0
0.078
27.2
1
0.078
S2
Figure S3. (A) Photograph of the as-prepared samples showing the color changes from green [NiGa
LDH and β-Ni(OH)2] to black (NiSe2). (B, C) Low-magnification SEM images of the as-converted
porous NiSe2 nanosheets.
Figure S4. (A) PXRD patterns of the β-Ni(OH)2 microplates after 20 h (black trace) and 42 h (red trace)
conversion reactions in Se and NaBH4 solution, indicating the product contains both NiSe2 and βNi(OH)2. The stars (*) mark the diffraction peaks from carbon paper substrate. (B, C) Low- and highmagnification SEM images of the β-Ni(OH)2 microplates after 20 h conversion reaction. (D, E) Lowand high-magnification SEM images of the β-Ni(OH)2 microplates after 42 h conversion reaction.
S3
Figure S5. (A) SEM image, (B) the corresponding EDS spectrum, and (C) PXRD pattern of NiSe2
nanosheets directly converted from NiGa LDH nanoplates. In this case, the etching of Ga3+ ions and the
conversion of β-Ni(OH)2 to NiSe2 took place simultaneously because the NaBH4 also produces NaOH
during the reaction. The pores in these as-obtained NiSe2 nanosheets are not very obvious, which is
because the NiGa LDH precursor used here has a higher Ni:Ga ratio of 5.5:1.
Figure S6. Illustration of the method for using Tafel plots for the extraction of the exchange current
density (j0) of the porous NiSe2 nanosheets for HER catalysis under both acidic and basic conditions.
The exchange current density (j0) was calculated by extrapolating the Tafel plots to the overpotential of
S4
0 V. The log |j0| values for porous NiSe2 nanosheets at pH 0 and pH 14 are −2.19 and −1.41, respectively,
and thus the corresponding j0 are 6.46 and 38.9 μA cm-2, respectively.
Table S2. Comparison of the catalytic performance of the porous NiSe2 nanosheets reported herein with
other recently reported high performance HER catalysts in both acidic and basic conditions.
Catalyst
Electrolyte
η @ 10 mA cm-2
(mV vs. RHE)
Tafel slope
(mV dec-1)
Exchange current
density (μA cm-2)
Ref.
porous NiSe2 nanosheets
0.5 M H2SO4
135
37.2
6.46
this work
NiSe2 thin film
0.5 M H2SO4
/
56.4~62.0
0.57~0.83
S1
CoSe2 nanoparticles
0.5 M H2SO4
137
42.1
4.9 ± 1.4
S2
CoSe2 nanoparticles
0.5 M H2SO4
140-270
31.2-61.1
/
S3
FeSe2 thin film
0.5 M H2SO4
/
62.1~71.6
0.27~0.47
S1
CoS2 nanowires
0.5 M H2SO4
145
51.6
15.1
S4
FeS2 thin film
0.5 M H2SO4
/
56.4
0.144
S5
Fe1-xCoxS2/carbon
nanotubes
0.5 M H2SO4
120 @ 20 mA cm-2
46
/
S6
NiS2 thin film
0.5 M H2SO4
/
48.8
0.0191
S5
1T-WS2 nanosheets
0.5 M H2SO4
142
70
/
S7
1T-MoS2 nanosheets
0.5 M H2SO4
195
43
/
S8
amorphous MoSxCly
0.5 M H2SO4
160
46
/
S9
porous CoP nanowires
0.5 M H2SO4
67
51
288
S10
WP2 submicroparticles
0.5 M H2SO4
161
57
17
S11
Ni2P nanoparticles
1 M H2SO4
~120
87
/
S12
MoSx/N-doped graphene
0.5 M H2SO4
140.6
105
/
S13
C3N4@N-Graphene films
0.5 M H2SO4
80
49.1
430
S14
Co/N-riched carbon
nanotubes
0.5 M H2SO4
260
80
10
S15
porous NiSe2 nanosheets
1 M KOH
184
76.6
38.9
this work
Co/N-riched carbon
nanotubes
1 M KOH
370
/
/
S15
Mo2C
1 M KOH
~ 192
54
3.8
S16
MoB
1 M KOH
~ 225
59
2.0
S16
porous CoP nanowires
1 M KOH
209
129
/
S10
WP2 submicroparticles
1 M KOH
153
60
/
S11
Ni2P nanoparticles
1 M KOH
~225
100
/
S12
S5
Catalyst
Electrolyte
η @ 10 mA cm-2
(mV vs. RHE)
Tafel slope
(mV dec-1)
Exchange current
density (μA cm-2)
Ref.
Ni-Mo nanopowder/Ti
foil
1 M NaOH
< 100
/
/
S17
Note: / -- not reported in the literature
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