Nickel-Sulfide-Derived high-performance

electrodes for supercapacitors by partial

ion-exchanged morphology genetic

Wutao Wei,† Liwei Mi,

*,‡,§ Yang Gao,

† Zhi Zheng,

§ Weihua Chen

*,† and Xinxin

Guan*,†

† College of Chemistry and Molecular Engineering, Zhengzhou University, Henan 450001, P. R.

China,

‡ Center for Advanced Materials Research, Zhongyuan University of Technology, Henan 450007,

P. R. China §

Key Laboratory for Micro-Nano Energy Storage and Conversion Materials of Henan Province,

Institute of Surface Micro and Nano Materials, Xuchang University, Henan 461000, P. R. China

Experimental Section

All chemical reagents in this work were of analytical grade and used without further purification.

In situ synthesis of 3D hierarchical nest-like NiS@Ni3S2 material

In the previous work, the effect of solvent ratio of ethylene glycol/anhydrous ethylenediamine on

the morphology of product has been explored in detail. But, what’s exciting is the first achieving

of nest-like NiS@Ni3S2 material with 3D hierarchical core-shell structure just through the change

of charging sequence. In a simple one-step solvothermal method, 0.5 mmol clean nickel foam

(0.0293 g), 7.5 ml ethylene glycol, 1 mmol sublimed sulfur (0.0321 g) and 8.5 ml anhydrous

ethylenediamine were placed in a 20 ml Teflon-lined autoclave subsequently. The autoclave was

then sealed off, maintained at 160 oC for 24 h and cooled down to room temperature naturally. The

product was removed from the solution and repeatedly washed with deionized water then 95%

ethanol. Finally, the as-prepared material as Sample 1 was dried in a vacuum oven at 60 oC for 8 h

and collected for further characterization.

Synthesis of 3D hierarchical nest-like Co9S8@Ni3S2 material

The 3D hierarchical nest-like Co9S8@Ni3S2 material was prepared by a morphology genetic

method using Sample 1 as a template. In order to the replacement products inheriting the

morphology of Sample 1 as well as possible, the solvent system and reaction temperature of

synthesis of Sample 1 were still choose in the replacement step, the differences were that nickel

foam and sublimed sulfur were replaced by Sample 1 and 0.5 mmol cobalt nitrate hexahydrate

(0.1450 g). According to this method, a series of replacement products were obtained with

different reaction time, that is to say, Sample 2, 3, 4, 5, 6, 7, 8, 9 and 10 were synthesized with

reaction time of 10 min, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, 12 h and 24 h. The post-treatment of these

materials were the same as Sample 1 and collected for further characterization.

Synthesis of 3D network NiSe2@NiS composite material

In previous work, CuSe@CuS and CuSe1.8@CuS composite materials was successfully

synthesized by the anion exchange method using the wool-ball-like CuS microflowers as the

template. Here, this idea will be used for reference to prepare nickel selenide by Se exchange with

3D hierarchical nest-like NiS@Ni3S2 material. As expected, the 3D network NiSe2@NiS

composite material with a special core-shell structure was first obtained by the anion exchange

with Se. In this work, a series of replacement products with Se were synthesized at 160 oC for

different reaction time using Sample 1 as the template, selenium powder as the selenium resources,

7.5 ml ethylene glycol and 8.5 ml anhydrous ethylenediamine as the mixed solution. So the

reaction time of Sample 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and 21, in order, are 1 h, 2 h, 4 h, 6 h,

8 h, 10 h, 12 h, 14 h, 16 h, 18 h and 24 h. The post-treatment of all these materials are the same as

Sample 1 and collected for further characterization.

Characterization.

X-ray diffraction (XRD) patterns were obtained with a Bruker D8 Advance X-ray powder

diffractometer using Cu-Kα irradiation at a scan rate of 0.1o s

-1. All XRD measurements were

performed within 15o

≤ 2θ ≤ 80o. The morphologies and sizes of the as-prepared materials were

characterized with a Zeiss EVO LS-15 scanning electron microscope (SEM) equipped with an

energy-dispersive X-ray spectroscopy (EDS) system. The nanostructures of the resulting samples

were recorded with a JEOL JEM-2010 transmission electron microscope (TEM). The samples for

the TEM and high-resolution TEM (HRTEM) analyses were prepared by removing the

as-obtained sample surface layer on the 3D formwork and dispersing the parings in C2H5OH. The

X-ray photoelectron spectroscopy (XPS) of the as-obtained Co9S8@Ni3S2 crystals was collected

using a Kratos AXIS ULTRA X-ray photoelectron microscope with Al-Kα X-rays as the excitation

source.

Electrochemical measurements

The electrochemical properties of the as-prepared samples were investigated with a CHI 604E

electrochemical workstation (Chenhua, Shanghai) under cyclic voltammetry (CV) measurements

with various voltage scan rates in a conventional three-electrode cell with 2 M KOH as the

electrolyte, Hg/HgO electrode as reference electrode, and Pt plate as the counter electrode,

respectively. The working electrodes were fabricated by mixing the active material (Sample 1, 9

and 20), acetylene black and binder (PVDF) in a weight ratio of 8:1:1, which was pressed at 20

MPa to a piece of nickel foam (1.0 cm×1.0 cm), and dried under vacuum at 60 oC for 10 h. The

galvanostatic charge-discharge tests were conducted on a LAND battery system (model CT2001A)

at various current densities. Specific capacitance could be calculated according to the following

equation: C = I∆t/m∆V, where I is charge or discharge current, ∆t is the time for a full charge or

discharge, m indicates the mass of the active material, ∆V represents the voltage window in a full

charge-discharge process.

Fig. S1 (a) TEM image of NiS nanorods on the surface of Sample 1. (b) TEM image of Co9S8

nanorods on the surface of Sample 9.

Fig. S2 (a-d) SEM images of Sample 2, 4, 6 and 10, respectively.

Fig. S3 XRD pattern of Sample 10.

Fig. S4 XRD pattern of Sample 21.

Fig. S5 The XPS spectra of (a) survey spectrum, (b) Ni 2p, (c) Co 2p for Sample 9. And the XPS

spectra of (d) survey spectrum, e) Ni 2p, (f) Co 2p for Sample 9 after the oxidation reaction during

the CV test at the scan rate of 0.05 mV/s.

Fig. S6 The variation of charge-discharge specific capacitance of Sample 1, 9 and 20 as a function

of cycle number from 1 to 18 at various current densities. Inset: the enlarge figure of the specific

capacity of cycle number from 2 to 18.

Fig. S7 The discharge specific capacitance curve of Sample 1, 3, 5 and 9 at different current

density.

Fig. S8 The variation of the specific capacity of Sample 1 and 9 with the number of cycles among

500 cycles at current density of 5 A/g.

Fig. S9 The first galvanostatic charge-discharge curve of Sample 1, 9 and 20 at the current density

of 0.5 A g-1

.

Table 1 the according table of the part sample and their component from the EDX.

Sample Number Component

1 NiS

(NiS@Ni3S2)*

2 Ni0.77Co0.23S

3 Ni0.62S0.38S

4 Ni0.4Co0.6S

5 Ni0.26Co0.74S

6 Ni0.17Co0.83S

7 Ni0.2Co0.8S

9 Ni0.19Co0.81S

(Co9S8@Ni3S2)*

11 NiS0.9Se0.1

14 NiS0.52Se0.48

17 NiS0.26Se0.74

20 NiS0.14Se0.86

(NiSe2@NiS)*

21 NiS0.15Se0.85

* The difference between the real component of samples and the EDX data was caused by the

limited penetration depth of EDX test.