Supporting Information Sulphur-source Inspired Self-grown 3-D NixSy Nanostructures and their Electrochemical Supercapacitors Nanasaheb M. Shinde, a Qi Xun Xia, a,c Pritamkumar V. Shinde, b Je Moon Yun, b Rajaram S. Mane, a* and Kwang Ho Kim a,b** a National Core Research Centre for Hybrid Materials Solution, Pusan National University, 30, Jangjeon-dong, Geumjung-gu, Busan 609-735, Republic of Korea b Global Frontier R&D Center for Hybrid Interface Materials, Pusan National University, 30, Jangjeon-dong, Geumjung-gu, Busan 609-735, Republic of Korea c School of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo454000, China. Corresponding Author. mane3796@pusan.ac.kr (Rajaram Mane, Prof.) * and kwhokim@pusan.ac.kr (K. H. Kim, Prof.) ** S-1
S1: The possible chemical reactions responsible for NixSy formation during the hydrothermal reaction conditions as a function of S 2- ion source precursor (1) Sodium thiosulfate (STS) Na2S2O3 is a reducing agent and whose half-cell reaction as S 2 O 2 3 S 4 O 2 6 + 2e (1) In aqueous medium, dissociation of STS take place S 2 O 2 3 + H + HSO 3 + S (2) The electron released (reaction (1)) react with sulphur from reaction (2) S + 2e S 2 (3) xni 2+ + ys 2 Ni x S y (4) (2) Thioactetamide (TAA) TAA solution which gives sulphide ions (S 2- ) and reaction follows In acidic medium protonation gives (5) The intermediate compound formed dissociates to give H2S as (6) (7) In aqueous medium H2S dissociates to give H 2 S H + + SH (8) SH H + + S 2 (9) Finally, S ions react with Ni ion to formed NixSy nanostructure S-2
xni 2+ + ys 2 Ni x S y (10) (3) Thiourea (TU) NH 2 CSNH 2 + 2H 2 O 2H 2 O + H 2 S + CO 2 (11) H 2 S + H 2 O 2H 2 O + + S 2 (12) xni 2+ + ys 2 Ni x S y (13) (4) Sodium sulfate (SS) Na 2 S 2Na + + S (14) xni 2+ + ys 2 Ni x S y (15) S2: Formulae used The areal capacitance (Ca), energy density (E) and power density (PD) were calculated from the discharge time of GCD curves using the equation as following Areal or gravimetric capacitance C = IΔt mδv (16) where, I is the discharge current, t is discharge time, m is for A is the area of geometrical electrode (1 1 cm 2 ) or mass of the active material and V is a potential window. The relation between energy density (E), power density (P) and volumetric capacitance (Cv) are calculated by the following equations: Energy density E = 1 2 CΔV2 (17) Power density P = E 3600 (18) Δt S-3
In this calculation formula, C is the specific capacitance of the NixSy-STS//Bi2O3device, V is the potential window (V), t is the discharging time. Figure S1. FE-SEM false images of NiF (a2) and self-grown NixSy superstructures [NixSy STS (b2), NixSy TAA (c2), NixSy TU (d2) and NixSy SS (e2)] at bar scale of 1 µm. S-4
Figure. S2: Show the false FE-SEM images, EDX mapping and spectrums of; (a-a3) NiF, (bb3) NixSy-STS, (c-c3) NixSy-TAA, (d-d3) NixSy-TU, and (e-e3) NixSy-SS. S-5
Figure. S3:FE-SEM images showing an uncomplete growth of; (a) NixSy-STS (1 gm), (b) NixSy-TAA (0.15 gm), (c) NixSy-TU (3 gm), (d) NixSy-SS (1.5 gm) superstructures at different magnifications. S-6
Figure. S4: XPS spectrums of; (a-a1) NiF, (b-b2) NixSy-TAA, (c-c2) NixSy-TU, (d-d2)nixsy-ss. S-7
Figure. S5: Nitrogen adsorption desorption isotherm and the pore-size distribution plots of; (a-a1) NiF, (b-b1) NixSy-TAA, (c-c1) NixSy-TU, (d-d1)nixsy-ss. S-8
Figure. S6: CV profile curves of; (a) NiF, (b)nixsy-sts, (c) NixSy-TAA, (d) NixSy-TU, (e)nixsy- SS at 5-25 mv s -1 scan rates, and (f) their comparative CV profiles at 25 mv.s -1 fixed scan rate. S-9
Figure. S7: (a-d) log i vs. logν plot slops are used for obtaining b, (a1-d1) i/v 1/2 vs. v 1/2 plots for estimating a1 and a2 ( at 0.2 v), and (a2-d2) capacitive and battery contributions of NiF, NixSy-TAA, Ni-TU, and NixSy-SS. S-10
Figure. S8: (A) EIS spectrums of; (a) NiF, (b) NixSy-STS, (c)nixsy-taa, (d)nixsy-tu, (e) NixSy- SSin the frequency range 0.01 HZ to 100 KHz ( inset shows its enlarge view EIS spectrum at higher frequency regions), and (B) cyclability test of NixSy-STS for 5000 cycle with inset as GCD curves after 1 st and 5000 th cycle. (C, D) FESEM images recorded at different magnifications showing the structural loss of NixSy. S-11
Sr. no Table S1. Comparative analysis of morphology, synthesis method and electrochemical energy storage performance of present work with previously reported Ni xs y electrodes. Working Synthesis Morphology Areal/Specific Stability (cycle) Ref. electrode method (deposition capacitance time) ( F.cm -2 / F.g -1 ) 1 Ni 3S 2 Solvothermal Pine-twig 670 F.g -1 97. 4% (2000) [S1] 2 NiS Self-oxidized Nanobrush 5.59 F.cm -2 94.9% (2000) [S2] 3 Ni 3S 2 Hydrothermal Nanosheet 694 F.g -1 89.3% (2000) [S3] 4 Ni 3S 2 Hydrothermal Nanoflake 7.25 F.cm -2 92.7% (5000) [S4] 5 Ni 3S 2 Hydrothermal Flower 1315 F.cm -2 85.6% (5000) [S5] 6 Ni 3S 2 Solvothermal Nanoporous 3.42 F.cm -2 102% (4250) [S6] 7 Ni 3S 2 Hydrothermal Graphene-like 1.342 F.cm -2 93.6% (4250) [S7] 8 Ni 3S 2 Hydrothermal Nest 1293 F.g -1 69% (1000) [S8] 9 Ni 3S 2 Solvothermal Flower 778.87 F.g -1 Not provided (3500) [S9] 10 Ni 3S 2 Hydrothermal Nanorod 7152 F.cm -2 94% (5000) Current Work S-12
Table S2. A comparative ASCs performance chart with energy density, power density, stability and stability information. Sr. No Device Energy Power Stability Ref. density Wh kg -1 density W kg -1 (cycle) 1 Ni 3S 2@β-NiS//AC* 55 925 97% (2000) [S1] 2 Ni 3S 2/MWCNT**- 19.8 798 90% (5000) [S10] NC//AC* 3 rgo-ni 3S 2//AC* 37.19 399.9 85% (5000) [S5] 4 Ni 3S 2//AC * 36 400 86% (1000) [S11] 5 NiS-NF//AC* 38.4 166.6 90% (1000) [S12] 6 rgo-nis//ac* 18.7 124 Not provided [S13] 7 Ni 3S 4/CC//AC* 14.6 750.8 84.7% (5000) [S14] 8 Ni 3S 2//Pen ink 8.2 214 93.1% (3000) [S15] 9 Ni xs y//bi 2O 3 41 1399 80% (5000) Present Work *CC- Carbon cloth; *AC- activated carbon; **MWCNT -Multiwall Carbon Nanotubes References S1. Li, W.; Wang, S.; Xin, L.; Wu, M.; Lou, X. Single-crystal β-nis Nanorod Arrays with a Hollow-structured Ni3S2 Framework for Supercapacitor Applications. J. Mater. Chem. A., 2016, 4, 7700 7709. S2. Li, X.; Chen, G.; Xiao, K.; Li, N.; Ma, T.; Liu, Z.; Z. Self-Supported Amorphous-Edge Nickel Sulfide Nanobrush for Excellent Energy Storage. Electrochim. Acta., 2017, 153 159. S3. Xiong, X.; Zhao, B.; Ding, D.; Chen, D.; Yang, C.; Lei, Y.; Liu, M. One-step synthesis of architectural Ni3S2 nanosheet-on-nanorods Array for use as High-performance Electrodes for Supercapacitors. NPG Asia Materials, 2016, 8, 300. S4. Yilmaz, G.; X. Lu, Direct Growth of 3 D Hierarchical Porous Ni3S2 Nanostructures on Nickel Foam for High Performance Supercapacitors. ChemNanoMat, 2016, 2, 719 725. S-13
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