Electronic Supplementary Information for

Hierarchical Graphdiyne@NiFe Layered Double Hydroxide

Heterostructures as a Bifunctional Electrocatalyst for Overall

Water Splitting

Hua-Yan Sia*, Qi-Xin Denga, Li-Chuan Chenb, Liu Wanga, Xing-Yu Liua, Wen-Shan

Wua, Yong-Hui Zhangd, Jin-Ming Zhouc*, Hao-Li Zhangb

Figure S1. a) Low-magnification SEM image of GDY@NiFe LDH/CF; b) Zoomed in structures

of GDY@NiFe LDH/CF in the corresponding positions marked in (a); c) and d) EDS mapping

images of GDY@NiFe LDH/CF.

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Figure S2. Energy-dispersive X-ray Spectra of GDY@NiFe LDH/CF.

Figure S3. a) and b) Low-magnification SEM image of NiFe LDH/CF with different area High-

resolution SEM images of c) NiFe LDH/CF and d) GDY@NiFe LDH/CF, respectively.

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Figure S4. XRD patterns of NiFe LDH, GDY and GDY@ NiFe LDH.

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Figure S5. a) XPS survey patterns of GDY@NiFe LDH/CF and GDY/CF. b) High resolution of

Ni 2p spectrum of GDY@NiFe LDH/CF. c) High resolution of Fe 2p spectrum of GDY/CF. d)

The XPS spectra of the C 1s of the GDY and the GDY@NiFe LDH sample. The binding energies

of e) Ni and f) Fe in GDY@NiFe LDH/CF, NiFe LDH/CF and NiFe LDH, respectively (Sat.

means shake-up satellites).

Figure S6. LSV curves of the GDY@NixFe-LDH samples, with x= 2, 3, 4, 5.

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Figure S7. Overpotentials of OER at current densities of 10, 20, and 30 mA cm−2 for the

GDY@NiFe LDH/CF, GDY@RuO2/CF and NiFe-LDH/CF samples.

Figure S8. AC impedance spectra of GDY@NiFe LDH/CF, GDY/CF and NiFe LDH at the

potential of 1.40 V (close to the OER onset potential in 1 M KOH).

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Figure S9. The morphology, oxidation state and the crystal structure of GDY@NiFe LDH/CF

after the long-term test for 50 h at a constant current density of 50 mA·cm−2. The SEM images of

a) OER and b) HER. The XPS spectra of c) Ni 2p and d) Fe 2p. e) The Raman spectra of before

and after OER. f) The XRD spectrum after OER.

Figure S10. The morphology of GDY@NiFe LDH/CF heterostructures after the water splitting

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test. a) Low-magnification SEM image; b) High-magnification SEM image.

Table S1. Comparison of some representative solid-state OER catalysts recently

reported for basic solutions.

CatalystsCurrent density j

(mA cm-2)

Overpotentials

(vs RHE) at the

corresponding j

Reference

Graphdiyne@NiFe LDH/CF 10 220 mV This work

e-ICLDH@GDY/NF 10 216 mV [1]

NiFe LDH@NiCoP/NF 10 220 mV [2]

NiCo2S4@NiFe LDH/NF 60 306 mV [3]

NiFe LDH-NS@DG10 10 210 mV [4]

MnO2-CoP3/Ti 10 288 mV [5]

Co-CuO/CF 50 299 mV [6]

Ni1.5Fe0.5P/CF 100 220 mV [7]

SrNb0.1Co0.7Fe0.2O3-δ 10 410 mV [8]

Exfoilated NiCo LDH 10 367 mV [9]

NiSe@NiOOH/NF 50 332 mV [10]

CoOx thin film 10 423 mV [11]

Table S2. Comparison of some representative solid-state HER catalysts recently

reported for basic solutions.

CatalystsCurrent density j

(mA cm-2)

Overpotentials

(vs RHE) at the

corresponding j

Reference

Graphdiyne@NiFe LDH/CF 10 163 mV This work

NiFe LDH-NS@DG10 20 115 mV [4]

NiFe LDH@NiCoP/NF 10 120 mV [2]

Ni(OH)2-PtO2 NS/Ti 4 31.4 mV [12]

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MnNi 10 360 mV [13]

Ni/MWCNT 10 350 mV [14]

CoOx@CN 20 134 mV [15]

Ni3S2/NF 10 223 mV [16]

Ni5P4 on Nickel foil 10 150mV [17]

NiCo2S4@NiFe LDH/NF 10 200 mV [3]

Table S3. Comparison of the electrochemical performances of GDY@NiFe LDH/CF

for overall water splitting in 1.0 M KOH with recently reported bifunctional

electrocatalysts.

CatalystsCurrent density j

(mA cm-2)

Overpotentials

(vs RHE) at the

corresponding j

Reference

Graphdiyne@NiFe LDH/CF 20 1.512 V This work

NiCo2S4 NW/GDF 20 1.560 V [18]

FeCoS–1 50 1.458 V [19]

NiFe LDH-NS@DG10 20 1.500 V [4]

NiFe LDH@NiCoP/NF 10 1.570 V [2]

NiFe LDH/Ni foam 10 1.700 V [20]

Ni1.5Fe0.5P/CF 20 1.635 V [7]

NiFe/NiCo2O4/NF 20 ~1.730 V [21]

EG/Co0.85Se/NiFeLDH 20 1.710 V [22]

NiCo2S4@NiFe LDH/NF 10 1.600 V [3]

CoFe LDH-F 10 1.630 V [23]

NiCoFe LTH/CC 10 1.550 V [24]

α-Co(OH)2 NA/CC 10 1.650 V [25]

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Figure S11 (a) CV conducted at the potential from 0.05 V to 0.15 V vs RHE at scan

rates of 10 mV/s, 20 mV/s, 30 mV/s, and 40 mV/s. (b) The current densities of the

anode and cathode measured at 0.1 V vs RHE at different scan rates.

Electrochemically active surface area (EASA) of catalyst is measured. The CV cycles

at different scan rates in the potential range from 0.0 V to 0.1 V vs RHE were

conducted to investigate the EASA of GDY@NiFe LDH/CF. The EASA was

estimated from the as obtained double-layer capacitance (Cdl). Cdl can be calculated

as:

Cdl=QU

=

dQdtdUdt

= jr(1)Q is the quantity of electric charge per unit area,

U is the voltage,

j is the current density and

r is the scan rate.

From Eq (1), the Cdl is the slope of j~r, which can be gained by the Figure S5b. The

average Cdl of GDY@NiFe LDH/CF is 9.015 mF/cm2. The EASA can be calculated

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as:

EASA=Cdl

C s(2)

The value of Cs is 40 μF/cm,2[4, 26-27] which is the specific capacitance value for a

falt standard with 1 cm2 of real surface area. Thus, the EASA for GDY@NiFe

LDH/CF is calculated as 225 cm2.

The calculation of Faradic efficiency

The Faradic efficiencies of HER and OER are calculated as the ratio of the amount of

experimentally collected gas to that of the theoretical result calculated from the charge

transfer.

Faradic efficiency can be calculated as:

Faraday Efficiency=m× n× FI × t

(3)

m is the moles of matter,

n is the number of electrons,

F is Faraday constant,

I is current in amperes,

t is time in seconds.

The gas was collected by water drainage method at a relative large current density of

60 mA cm-2 for 5 hours using a 1 cm2 of real surface area electrode. The faradaic

efficiency for HER was calculated as 96.2% (120.5 mL hydrogen collected). While

the faradaic efficiency for OER was 98.2% (61.5 mL oxygen collected).

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