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Rapid ambient growth of copper sulfide microstructures: Binder free electrodes for supercapacitor
Journal of Energy Storage 28 (2020) 101288
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Rapid ambient growth of copper sulfide microstructures: Binder free electrodes for supercapacitor Sajeeda Shaikh, M.K. Rabinal
T
⁎
Department of Physics, Karnatak University Dharwad, Karnatak 580003, India
ARTICLE INFO
ABSTRACT
Keywords: Copper sulfide films Supercapacitor Specific capacitance Specific energy Specific power
Metal chalcogenides are earth abundant, low cost, and less toxic materials with a good electrochemical activity and hence can be ideal materials for high performance supercapacitors. Here the copper sulfide is successfully deposited on copper foil by a rapid and ambient chemical route to form highly oriented and uniform microstructures. These films are adherent with a high surface area and porosity and also electrically conducting, hence can be used as binder free electrodes for supercapacitors. These devices were constituted with KOH as an electrolyte, which show a good electrochemical performances; specific capacitance 1173 Fg−1 at 1 mVs−1, specific energy 301.4 Whkg−1, and specific power 1400 Wkg−1 with a good cyclability. Hence, the proposed technique is simple and cost effective to form high performance supercapacitors.
1. Introduction The World's energy crisis is the result of limited utilization of alternative energy resources. The conventional energy resources, which contribute almost up to 80% of our energy demands are rapidly consumed due to industrial revolutions, population explosion and economic growth [1,2]. Such a huge consumption creates a high carbon emission that has severe negative impacts on health and the environment. Hence, over the last few decades, energy research is mainly focused on clean and greenways of energy generation and storage using renewable energy resources [3]. Among these resources, the solar energy is abundant, clean, regular and convertible in various ways. However, it is intermittent and poses several challenges associated with energy storage systems. At present, the energy storage/conversion through electrochemical methods is one of the interesting technologies, which includes mainly batteries and supercapacitors [4]. Supercapacitors are needed as sustainable and renewable power sources and have attracted a lot of attention due to their ultrafast charge/discharge capability, long cycle life, reversibility, high power density, moderate energy density, safe operation, and eco-benignity. Further, the complementation of batteries and supercapacitors helps to develop high energy density and high power density energy storage systems [5]. Electrochemical supercapacitors are b divided into two types one is the double layer capacitors (non-Faradaic) and another is pseudo-capacitors (Faradaic). Due to fast and fully reversible redox reactions, the latter exhibits a higher specific capacitance. The transition metal
⁎
Chalcogenides, such as CuS, MoS2, CdSe, Ni3S4, etc. have been widely studied compounds as supercapacitor electrode materials [6]. A good electrode must possess a high surface area, controlled porosity, fast charge/discharge cycles, a high conductivity, chemically stable and cost-effective [7]. Presently the best known electrodes, which include RuOx, MnO2, MoS2, Fe3S2, Ni3S4, conducting polymers/composites, etc. do not meet all the criteria, further some of these materials require a complex method of syntheses [8–14]. Hence, it is highly desirable to develop the electrodes which are earth abundant and easy to make in on large scale at a lower cost. In this respect, thin films of various materials on a given substrate have become attractive options due to least series resistance that enhance the power density [15]. Besides, the electrodes must also have a high electrolyte accessible network, which accelerates the ion transport during the charging/discharging process with a good retention rate. Conventional electrodes are fabricated by casting slurry of electroactive material and binder on the current collector, the latter include certain organic materials, polymers, etc. [16]. Often, the binder severely affects the electrical conductivity and ion accessibility in active material [17]. Binder-free electrodes using solution phase synthesis are now at the peak of research, wherein a directly in-situ single-step growth of nano/micro-architectures on current collector provides a highly efficient electron high ways that may significantly enhance the rate capability of supercapacitors. Some of the current collectors such as carbon, stainless steel, titanium, copper, silicon, nickel, and their nano/micro structures are successfully used for the creation of binder-free electrodes [18]. Such electrodes promote
Corresponding author. E-mail address: [email protected] (M.K. Rabinal).
https://doi.org/10.1016/j.est.2020.101288 Received 19 December 2019; Received in revised form 4 February 2020; Accepted 12 February 2020 Available online 25 February 2020 2352-152X/ © 2020 Elsevier Ltd. All rights reserved.
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal
easy diffusion and transportation of ions which enhances the electrochemical performance. In this respect, the metal chalcogenides such as CuS (CuxS, x = 1–2), MoS2, Co9S8, NiS, Ni3S2, WS2, etc. have become attractive electrode materials [19–22]. Particularly the metal-sulfides due to better electrical conductivity, a large crystal unit cells, and low electronegativity and complex valence of sulfur, these compounds show an excellent electrochemical performance as compared to other metal sulfides/oxides [23,24]. Theoretically, it is predicted that copper sulfides may exhibits a high specific capacitance as compared to other metal sulfides [25–26]. It is known that CuxS (x = 1–2) exhibit a wide variety of metastable and mixed phases, in which the location of Cu atoms/ions in the close-packed ‘S’ lattice are not well identified, the position of these ions change with composition. The known CuxS metastable phases are: Villamanite (CuS2), Covellite, in the “sulfur-rich region”; and Yarrowite (Cu1.12S), Spinkopite (Cu1.39S), Gerite (Cu1.6S), Anilite (Cu1.75S), Digenite (Cu1.8S), Djurleite (Cu1.95S), Chalcocite (Cu2S), in the “copper-rich region”. Among these phases, Cu2S and Cu1.75S are considered to be more promising electrode materials [27–28]. There are current attempts to explore these materials for supercapacitor applications. Wei et al. proposed the growth of copper sulfide (CuS) microspheres directly on a copper foil via redox reaction between CuSO4 and Na2S2O3 that shows the specific capacitance of 1443 F-g−1at current density of 1 A-g−1 [29], Zhang et al. proposed the growth of copper sulfide nano-walls on nickel foam via hydrothermal method with a good electrochemical performance, demonstrating the specific capacitance close to 1124 F-g−1 at current density of 15 mAcm−2 with a good cyclability [30]. Further, the combination of CuxS phases with other nanostructures of carbon, conducting polymers and metal foams have shown a dramatic improvement in the values of specific capacitance [31]. However, the CuS phases suffer with certain drawbacks, like low intrinsic conductivity (~10−3 S-cm−1) as compared to other electrode materials such as carbons and conducting polymers, difficulty in phase pure synthesis, lack of schematic tuning of porosity for better electrochemical accessibility of ions, poor interfacial kinetics, the low stability due to irreversible volume change during electrochemical cycling, etc. [32]. Further, many of existing synthetic techniques on these materials are carried out at elevated temperatures [33]. Still, the novelties in (on) large scale, ambient, and low cost syntheses are highly desirable aspects. The present work is focussed to synthesize highly active copper sulfide on copper foil by a simple and quick reaction process just at ambient condition, which results into promising electrode material for supercapacitors.
sulfide. After the reaction, the foil is taken out and rinsed several times with deionized water and dried in an open atmosphere. It is observed that the thickness of film gradually increased with reaction time, but it losses adherence as it becomes thicker. Therefore the above procedure is standardized after a couple of trials. This reaction is carried out for different concentrations of sulfur and it is concluded that increased molarity of sulfur accelerates the reaction and resulting in the thicker films, hence the rate of reaction and film thickness increases with an increase in molarities from 0.01 M to 0.1 M. In the present work, the concentration and time are restricted to 0.03 M and 5 min, respectively, which results in highly adherent and uniform films. The mass of active material grown on the copper foil can be determined by taking the mass difference of copper foil before and after the growth of copper sulfide film with a suitable correction to the chemical composition. 3. Cell assembly and electrochemical measurements As prepared copper sulfide electrodes were used for electrochemical measurements by forming a symmetric capacitor. Typically 2 M aqueous KOH is used as an electrolyte and Watmann filter paper of 200 µm (thick) as a separator which is soaked in an electrolyte and sandwiched between the above electrodes. Cyclic voltammetry (CV), Galvanostatic charge/discharge (GCD), impedance measurements were carried out using electrochemical work station (CHI660E, CHI Instruments, USA). A supercapacitor is constituted using our homemade setup, the details of which are given elsewhere [34]. The room temperature cyclic voltametry measurements were carried out at various scan rates ranging from 1 mV-S−1 to 50 m-Vs−1 with a working potential window of (−1 to 0.8) V0. The quantitative specific capacitance is estimated from cyclic voltamograms using the following Eq. (1) [35–37].
CS =
1 × 2×S× V×m
vf
I dI
(1)
vi −1
where, Cs is the specific capacitance of the material (F-g ), I represents the current, ΔV, is the working potential window, m is an active mass of the active electrode materials (weight of both the electrodes), S is the scan rate, vi and vf are the initial and final voltages scanned window, respectively. Specific Capacitance is also estimated using discharge curve by Galvanostatic charge/discharge measurements. Here Cs is estimated using Eq. (2).
Cs =
2. Experimental details
I× t m× V
(2)
where I is the applied current, Δt is the discharge time, m is the total mass of active materials, and ΔV is the applied potential window. On the basis of mass of active electrode material the overall performance and efficiency of an electrode is determined through specific energy density (E (Wh- kg−1)) and specific power density (P (W-kg−1)) parameters, which can be calculated from the Eq. (3) and (4), respectively.
Commercial Copper foil (purity 99.99%), 0.17 mm thick (20 mm × 20 mm) is used as a source of copper and substrate, sulfur powder was obtained from sd-Fine chemicals, India, which is used as an elemental source for sulfurization, and hydrazine hydrate (NH2NH2.H2O) is obtained from Spectrochem, India. All the chemicals used in this work are of AR grade and are used as received without further purification. Deionized water is used throughout the work and all the syntheses were carried out at room temperature. In a typical synthesis, initially 0.03 M of 20 ml of sulfur solution is prepared by dissolving 1.9 mg of sulfur powder in 0.2 ml of hydrazine hydrate and further diluted by adding deionised water. A copper substrate of dimension (2 cm × 2 cm × 0.17 mm) is well cleaned using HCl and acetone to remove the surface oxide. The copper foil is horizontally immersed into the sulfur-hydrazine hydrate complex, at room temperature for 5 min to grow copper sulfide on copper foil. The reaction bath is placed at room temperature for 5 min. There is a rapid formation of the dark-gray film indicating the formation of copper
E = 0.5 × Cs × ( V )2 P=
E t
(3) (4)
4. Results and discussion The copper sulfide nano/microstructure grown on the copper foil is schematically represented in Fig. 1(a), which illustrates the synthetic procedure and indicates the simplicity of the present method. The copper foil is immersed in sulfur-hydrazine hydrate complex solution, immediately a dark gray film grows on the surface of copper. The
2
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal
Fig. 2. X-Ray diffraction pattern of as prepared copper sulfide.
of sulfur as well as coordinating agent to form the above complex, also it facilitates the reaction between copper and sulfur. The use of hydrazine hydrate-sulfur complex has been successfully utilized by our group for the past few years to synthesize highly oriented copper sulfide dendrites for thermoelectric and other applications [38], the details of which is given in our earlier reports. This route is also used in the synthesis of cadmium sulfide nanoparticles with tunable particle size [39]. It is expected that surface atoms on copper foil react with hydrazine hydrate complex to form copper sulfide. When the coordinated copper ions from the substrate react with the complex of sulfur ions initially a thin layer of copper sulfide is formed on the substrate, later the sulfur ions migrate and react with unreacted copper present below the sulfide film leading to inward growth of higher morphological structures. Prepared films are structurally porous, so it is expected that sulfur ions may reach unreacted copper even after the formation of copper sulfide film that results in a highly porous copper sulfide films of desired thickness. The photographic image of copper sulfide microstructures on copper substrate is shown in Fig. 1(b), which displays the good adherence and flexibility of these films, even with bending close to 360° it still remains in contact with foil. Hence, the present synthetic method provides a highly adherent copper sulfide electrode. Next, the crystal structure of as-grown film is studied by recording powder X-ray diffraction using Philips X'Pert powder diffractometer with CuKα radiation (λ = 1.54056 Å), a typical powder pattern is shown in Fig. 2, the peaks are well indexed with hexagonal Anilite (Cu1.75S) phase when compared with the standard data file (JCPDS: card no.33-0489). It matches with characteristic planes of (202), (220), (131), (100), (304), and (305) and all the peaks are quite sharp. This observation, clearly confirms that the as-prepared film is phase pure
Fig. 1. (a) A schematic representation of copper sulfide formation on a copper electrode, (b) A real image of copper sulfide film deposited on a copper plate.
probable chemical reaction can be as follows.
(5) and highly crystalline in nature. The surface morphology of these films is studied with a field emission scanning electron microscope (FESEM) (JEOL-JSM-6700F), with the acceleration voltage of 15 kV. The typical images are shown in Fig. 3(a) and (b) for bare copper and deposited
In this reaction process, the hydrazine hydrate reacts with sulfur to form sulfur-hydrazene hydrate complex. This complex is air stable and quite suitable for the synthesis of sulfur based nanoparticles by an aqueous route. Here, hydrazine hydrate works as a solvent for dilution 3
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal
Fig. 4. (a) Cyclic voltamograms of the copper sulfide electrode based supercapacitor at different scan rate in 2 M KOH solution, (b) The Specific capacitance measured at different scan rates.
to enhance the specific capacitance of supercapacitors. These peaks are caused by the redox reactions of copper sulfide surface species with an alkaline electrolyte and is directly related to the oxidation state of Cu at high concentration of electrolyte [40]; it can be seen from the figure that the cathodic and anodic peaks shift to lower and higher potentials with increase in scan rates, which is quite typical in kinematical process and is also referred as intercalation/deintercalation of the ions at the electrode-electrolyte interface where the peak current (ip) is linearly proportional to the square root of scan rate, commonly referred as the Radels-Sevick effect [41]. The area under curve increases with increase in scan rate and the redox peaks are still observed even at the higher scan rate of 50 mV s−1, which indicates that crystalline structures of copper sulfide are beneficial for fast reversible redox reactions with good electrolytic efficiency in KOH electrolyte. The Cs is calculated from these curves using Eq. (1) for different scan rates and the same has been shown in Fig. 4(b) which is a typical behavior for electrochemical supercapacitors. The specific capacitance of 1173 Fg−1 is obtained at 1 mVs−1, which decreases to 540 Fg−1 at the scan rate 50 mVs−1. The galvanostatic charge/discharge is used to estimate the electrochemical capacitance as well as the cyclability. The charge-discharge curves of these devices are plotted in Fig. 5(a), it is evident from the nonlinear behavior of charging/discharging curves the redox reactions do play an important role in these devices [42,43]. The specific capacitance is calculated from these charge-discharge curves, using Eq. (2). At different discharge currents, the specific capacitance is 1355 Fg−1, 1107 Fg−1, 973 Fg−1, 517 F g−1 at 2 Ag−1, 3 Ag−1, 5 Ag−1, 15 Ag−1 respectively, is much higher than the previously reported literature values on copper sulfide alone. As the current density increases the discharge time decreases, also the specific capacitance decreases with
Fig. 3. FESEM image of copper sulfide film (an inset shows a high magnification image view). (a) Bare Copper Foil, (b) Copper Foil with Copper sulfide deposition.
films of copper sulfide, respectively. Here the size and deposition of copper sulfide is quite uniform over the entire film area. The inset in the same figure is high resolution FESEM image of the same, which illustrates 3D-hexagonal morphology. Such large surface area forms due to thin mesoporous nanostructures resulting into more electroactive sites for faradic energy storage and it ensures good mechanical adhesion and electrical connectivity with a current collector. Further, the large crystalline structure of CuxS efficiently allows the electrolyte ions to access the active surface area. Such a simple chemical scheme that allows the easy formation of active materials on current collectors and avoids the use of polymer binders with enhanced porosity has a definite advantage. Besides this, the binders always lead to low electrical conductivity and put the adverse effect on electrode material with unnecessary dead mass. Next, the symmetric supercapacitors are constituted using these electrodes with KOH as an electrolyte, as mentioned above in the experimental section. Cyclic voltametry measurements were carried out and their results are shown in Fig. 4. These curves are recorded for different scan rates with a potential window of −1 V to 0.8 V, these curves are different from quasi rectangular nature that is typical in the case of electric double layer capacitors (EDLC). The as-prepared copper sulfide electrodes showed a multiple numbers of redox peaks, which are due to pseudocapacitance behavior, which is an essential requirement 4
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal
Fig. 6. Electrochemical impedance curve (Nyquist plot) for copper sulfide electrode based supercapacitor.
has been shown in Figure S1 as the supporting information. This clearly reveals that Cu1.75S can be a good electrode for electrochemical supercapacitors. The electronic conductivity and ionic diffusion at the interface between electrolyte and electrodes can be studied by electrochemical impedance spectroscopy (EIS). These measurements are carried out in the frequency range from 0.1 Hz to 1 MHz at a potential of 10 mV. The imaginary impedance (Zʹʹ) versus real impedance (Zʹ), that is referred as the Nyquist plot, is shown in Fig. 6, the equivalent circuit of the device and the computed z-fit for an open circuit potential with AC perturbation of 5 mV are also shown in the same figure as an inset [47]. There is a good fit between experimental data and the calculated curve. Further, these measurements show a partial semicircle at a high frequency and an inclined line at low frequency. The semicircle diameter at high-frequency equals to the charge transfer resistance (Rct) at the electrolyte-electrode interface and is also called as faraday resistance which is a limiting factor for the specific power of a supercapacitor which is attributed to the faradic reaction(s). From the diameter of the semicircle arc, the Rct can be estimated and it is 10 Ω, this clearly demonstrates that electrons have a better charge transfer property in these electrodes and hence a good pseudocapacitive behavior. The above magnitude of Rct is typically observed in the Cu1.75S based supercapacitors, it is in the range of 12.4 Ω to 15 Ω [48,49]. The x-intercept of the Nyquist plot corresponds to the equivalent series resistance (Rs) and it is estimated to be 2 Ω, which has various contributions like internal resistance of the electrode, ionic resistance of the electrolyte, and resistance of the interface between electrode and electrolyte. Hence, it has components of both ions and electrons. As mentioned earlier in the introduction the copper sulfide microstructures are seriously explored as electrode materials for energy storage applications, particularly for electrochemical supercapacitors. The copper sulfide exhibits close to nine phases, of which Cu2S and Cu1.75S are considered as better materials [50]. In general, the major work on copper sulfides as electrodes for supercapacitors has been summarized in the Table 1, where the parameters like synthesis method, morphology, and electrochemical performance are mentioned. There is limited work on pure copper sulfide as supercapacitor electrodes; such devices exhibit the typical specific capacitance in the range 250 F-g−1 to 400 F-g−1. A superior value of 1443 F-g−1 at 1 A-g−1 has been reported in the case of well structured microspheres of CuS on copper foil that was grown by chemical deposition for 18 h. However, the suitable combination of copper sulfide phases with other nanostructured materials such as carbon (QDs, CNTs, MWCNTs, r-GO, etc.), conducting
Fig. 5. (a) Galvanostatic charge/discharge curves of the copper sulfide electrodes at 2 Ag−1, 3 Ag−1 and 5 Ag−1, 15 Ag−1 in 2 M KOH electrolyte, (b) Stability performance curve, specific capacitance retention. Potential Vs Cycle Number.
an increase in current density, which concludes that ions of the electrolyte have insufficient time to diffuse into the active material. Further, the decrease in specific capacitance with increase current density is due to electrode resistance and insufficient Faradaic reaction at higher discharge current densities. Such a decrease in capacitance is also associated with a change in shape, loss of active surface area and alteration of resistance during charge/discharge processes [44,45]. A long cycling life is another important requirement, which depends on the stability of as-prepared electrode material. In this context, the cycling life test is carried out by performing galvanostatic charge/discharge measurements at a current density of 2 Ag−1 for more than 3000 cycles. Fig. 5(b) represents these stability test measurements, for clarity the data here is shown only for the first 1500 charge/discharge cycles, interestingly the specific capacitance stays stable and it goes from 100% to slightly down that is 99%, the values in between these cycles show distortion, this could be due to the formation of ion concentration gradient at the electrode/electrolyte boundary that eventually retards the diffusion of ions into the material [46]. The repeated C-V measurements of these devices with a large number of cycles showing a negligible change confirm that the material is stable. However, in order to check this, after complete characterization for more than 1500 cycles the Cu1.75S powder from the electrode surface was recovered and repeatedly washed with water to perform the XRD. It is observed that there is no noticeable change in the crystalline structure of as prepared and used material, which clearly shows that the material is stable, this 5
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal
Table 1 Summarizes the recent literature on the use of copper sulfide phases as an electrode material for supercapacitors along with their references. Sl No 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
Material CuS-nanoarrays @ Cu foil CuS-nanoarrays @ Cu mesh CuS-microspheres @ Cu foil CuS nanotubes –MWCNT @ carbon paper Cu7.2S4- microspheres @ Ni foam Cu1.92S-nanorods & CuS-nanoribbon @ Cu foam Cobalt doped CuS – nanoflowers @ glassy carbon electrode CuS-rGO- flower like @ Ni foam CuS –nano hollow spheres @ Ni foam CuS-nanowalls @ Ni- foam CuS-microspheres / CNT @ Ni foam Acetylene black/CuS- nanosheets @ Ni foam Carbon Dot/CuS/GO- Hydrogels @ stainless steel point cell CuS/rGO/Ni3S2 nanoarrays CuS-polypyrrole @ bacterial cellulose membrane CuS nanosheets- MWCNT @ Ni foam CuS- nanoflower @ Ni- foam
Method of synthesis wet-chemical synthesis at 80 °C Two step chemical synthesis Chemical deposition (18 h) Two step ion exchange Two step ion exchange Chemical etching method at 80°C Hydrothermal process at 130°C for 10 h Hydrothermal process at 180°C for 12 h Hydrothermal at 160°C for 24 hrs Hydrothermal at 80°C for 12 h Two step-ion exchange 160°C and 80°C Solvothermal synthesis Hydrothermal process at 180°C for 12 h Hydrothermal process @ 160°C 12 h Insitu oxidative polymerization & solvothemal process Hydrothermal process at 180°C for 72 h Solvothermal @ 80 °C
polymers, bacterial cellulose, and metal foams exhibit a superior specific capacitance that ranges from 300 F-g−1 to 2981 F-g−1. A significantly much higher value of 5029 F-g−1 at 4 A-g−1 has been also reported in the case of CuS-nanoflower on Ni- foam grown by a solvothermal route at 80 °C [51]. It is too high as compared to the best possible values that are reported for various advanced materials and hence it deserves further investigations. The best recent reported values of specific capacitance in the case of carbon, conducting polymers, metal oxides, and their composites are ⁓600 F-g−1, 3500 F-g−1, 4000 F-g−1, 2500 F-g−1 respectively [52,53]. Finally, the Cu1.92S is a suitable electrode material for supercapacitors. It is identified from the literature that smaller the value of charge transfer resistance and series resistance higher will be the power density of supercapacitors [54]. Since the as prepared Cu1.75S nano/ micro structured film has high porosity, the electrolyte ions are easily accessible to electrodes and thereby the charge transfer resistance is lowered. Based on the above electrochemical performance, the obtained Cu1.75S electrodes in this work are apparently superior to many of the previously reported copper sulfide based materials. Hence, the present results clearly suggest that Cu1.75S is a good electrode material to constitute supercapacitors. The present devices exhibit a high pseudo electrode capacity close to 1173 F-g−1, a better specific power 1400 WKg−1, specific energy 301 Whkg−1and excellent rate capability, which are important parameters of supercapacitors.
Performance −1
Refs. −2
305 F-g at 2 mA-cm 378.0 mF-cm−2 −1 at 1 A g−1 1443 F-g 636.28 F-g−1 at10 Ag−1 245.5 F-g−1 at 5 mVS−1 448 F-g−1 at 5 mA-cm−2 586.45 F-g−1 at 5 mV/S 368.3 F-g−1 at 1 Ag−1 948 F-g−1 at 1 A g−1 1124 F-g−1 at 15 mA-cm-2 1960 F-g−1 @ 10 mA-cm−2 2981 F-g−1 at1 Ag−1 920 F-g−1 at 1 Ag−1 1692.7 F-g−1 at 6.5 A g−1 580 F-g−1at 1 mA-cm−2 2800 F-g−1 at 1 Ag−1 5029 F-g−1 at 4 Ag−1
[59] [65] [29] [66] [62] [61] [58] [55] [18] [30] [64] [37] [57] [63] [56] [60] [51]
Methodology, Validation, Writing - original draft, Writing - review & editing. Declaration of Competing Interest None. Acknowledgments One of the authors Miss Sajeeda Shaikh gratefully acknowledges the fellowship support under DST- Purse Phase-II programmes, New Delhi, Govt. of India. Supplementary materials Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.est.2020.101288. References [1] F. Wang, X. Wu, X. Yuan, a Zaichun Liu, Y. Zhang, L. Fu, Y. Zhu, Q. Zhou, Y. Wu, Wei Huang, Latest advances in supercapacitors: from new electrode materials to novel device designs, Chem. Soc. Rev. 46 (2017) 6816–6854, https://doi.org/10. 1039/c7cs00205j. [2] .. M.Sevilla, R. Mokaya, Energy storage applications of activated carbons: supercapacitors and hydrogen storage, Energy Environ. 7 (2014) 1250–1280, https://doi. org/10.1039/c3ee43525c. [3] H. Zhao, L. Liu, R. Vellacheri, Y. Lei, Recent advances in designing and fabricating self-supported nanoelectrodes for supercapacitors, Adv.Sci. 4 (2017), https://doi. org/10.1002/advs.201700188. [4] E. Talaie, P. Bonnick, X. Sun, Q. Pang, X. Liang, L.F. Nazar, Methods and protocols for electrochemical energy storage materials research, Chem. Mate (2017) 90–105, https://doi.org/10.1021/acs.chemmater.6b02726. [5] C.J. Hung, P. Lin, T.Y. Tseng, High energy density asymmetric pseudocapacitors fabricated by graphene/carbon nanotube/MnO2 plus carbon nanotubes nanocomposites electrode, J. Power Sources 259 (2014) 145–153, https://doi.org/10. 1016/j.jpowsour.2014.02.094. [6] B.K. Kim, S. Sy, A. Yu, J. Zhang, Handb. electrochemical supercapacitors for energy storage and conversion, Clean. Energy Syst. (2014) 1–25, https://doi.org/10.1002/ 9781118991978.hces112. [7] Yongkun Liu, Guohua Jiang, Zheng Huang, Qiuling Lu, Bo Yu, Uwamahoro Evariste, and Pian Pian M., Decoration of hollow mesoporous carbon spheres by NiCo2S4 nanoparticles as electrode materials for asymmetric supercapacitors, ACS applied Energy Material, doi: 10.1021/acsaem.9b01569. [8] H. Kwon, D. Hong, I. Ryu, S. Yim, Supercapacitive properties of 3D-Arrayed polyaniline hollow nanospheres encaging ruo2 nanoparticles, ACS Appl. Mater. Interfaces 9 (2017) 7412–7423, https://doi.org/10.1021/acsami.6b14331. [9] S. Sun, G. Jiang, Y. Liu, Y. Zhang, J. Zhou, B. Xu, Growth of MnO2 nano particles on hybrid carbon nano fibers for flexible symmetrical supercapacitors, Mater. Lett 197 (2017) 35–37, https://doi.org/10.1016/j.matlet.2017.03.092 doi.org/. [10] S. Palsaniya, H.B. Nemade, A.K. Dasmahapatra, Synthesis of polyaniline/graphene/ MoS2 nanocomposite for high performance supercapacitor electrode, Polymer (Guildf) 150 (2018), https://doi.org/10.1016/j.polymer.2018.07.018. [11] S.P. Guo, J.C. Li, J.R. Xiao, H.G. Xue, Fe3S4 nanoparticles wrapped in an rGO matrix for promising energy storage: outstanding cyclic and rate performance, ACS
5. Conclusions Herein a simple room temperature binder free chemical route has been developed to form highly adherent, hydrophilic nano/microstructures of Cu1.75S on a copper plate as an electrode material for supercapacitor. These devices are constituted using above electrodes with KOH as an electrolyte; these exhibit an excellent supercapacitive performance, giving specific capacitance 1173 F-g−1 at 1 mV-s−1 and excellent rate capability close to 99% and good cycle life. The superior electrochemical behavior has been attributed to the interconnected network of Cu1.75S, which provides efficient transport pathways for both electrons and electrolytic ions during the charge/discharge processes of these devices. Eventually, this leads to superior current capacitive behavior and better cycling performance. The work is simple, cost-effective and easily scalable techniques to form binder-free copper sulfide for electrochemical energy storage applications. CRediT authorship contribution statement Sajeeda Shaikh: Data curation, Software, Writing - original draft, Writing - review & editing. M.K. Rabinal: Conceptualization, 6
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[12]
[13] [14]
[15]
[16] [17] [18] [19]
[20] [21]
[22]
[23] [24]
[25] [26] [27] [28]
[29]
[30]
[31]
[32]
[33] [34]
[35] [36]
Appl. Mater. Interfaces 9 (2017) 37694–37701, https://doi.org/10.1021/acsami. 7b10406. H. Wang, M. Liang, D. Duan, W. Shi, Y. Song, Z. Sun, Rose-like Ni3S4 as batterytype electrode for hybrid supercapacitor with excellent charge storage performance, Chem. Eng. J. 350 (2018) 523–533, https://doi.org/10.1016/j.cej.2018.05.004 doi. org/. S. Sun, G. Jiang, Y. Liu, B. Yu, U. Evariste, Preparation of α-MnO2/Ag/RGO hybrid films for asymmetric supercapacitor, J. Energy Storage 18 (2018) 256–258, https:// doi.org/10.1016/j.est.2018.05.010. B. Yu, G. Jiang, W. Xu, C. Cao, Y. Liu, N. Lei, U. Evariste, P. Ma, Construction of NiMoO4/CoMoO4 nanorod arrays wrapped by Ni-Co-S nanosheets on carbon cloth as high performance electrode for supercapacitor, J Alloys Compd 799 (2019) 415–424. Dan Feng, Yingying Lv, Zhangxiong Wu, Yuqian Dou, Lu Han, Zhenkun Sun, Yongyao Xia, Gengfeng Zheng, Dongyuan Zhao, Free-Standing mesoporous carbon thin films with highly ordered pore architectures for nano devices, J. Am. Chem. Soc 133 (2011) 15148–15156, https://doi.org/10.1021/ja2056227 doi.org/. B. Song, F. Wu, Y. Zhu, Z. Hou, K. sik Moon, C.P. Wong, Effect of polymer binders on graphene-based free-standing electrodes for supercapacitors electrochim, Acta 267 (2018) 213–221, https://doi.org/10.1016/j.electacta.2018.02.072 org/. C. Yuan, J. Li, L. Hou, X. Zhang, L. Shen, X.W. Lou, Ultrathin mesoporous NiCo2O4 nanosheets supported on ni foam as advanced electrodes for supercapacitors, Adv. Funct. Mater 22 (2012) 4592–4597, https://doi.org/10.1002/adfm.201200994. H. Heydari, S.E. Moosavifard, S. Elyasi, M. Shahraki, Nanoporous CuS nano-hollow spheres as advanced material for high-performance supercapacitors, Appl. Surf. Sci. 394 (2017) 425–430, https://doi.org/10.1016/j.apsusc.2016.10.138 org/. Muhammad Sufyan Javed, Shuge Dai, Mingjun Wang, Donglin Guo, Lin Chen, Xue Wang, Chenguo Hu, Yi X., J.solid state flexible supercapacitor based on molybdenum sulfide hierarchical nanospheresPower sources, 285, (2015) 63–69, doi:org/10.1016/j.jpowsour.2015.03.079. H. Li, Y. Gao, Y. Shao, Y. Su, X. Wang, Vapor-Phase atomic layer deposition of Co9S8 and its application for supercapacitors, Nano Lett 15 (2015) 6689–6695, https://doi.org/10.1021/acs.nanolett.5b02508. Xiaoyan Yan, Xili Tong, Lei Ma, Yuming Tian, Yuesheng Cai, Changwei Gong, Mingang Zhang, Liping Liang, Synthesis of porous NiS nanoflake arrays by ion exchange reaction from NiO and their high performance supercapacitor properties, Mater. Lett 124 (2014) 133–136, https://doi.org/10.1016/j.matlet.2014.03.067 org/. S. Ratha, C.S. Rout, Supercapacitor electrodes based on layered tungsten disulfidereduced graphene oxide hybrids synthesized by a facile hydrothermal method, ACS Appl. Mater. Interfaces 5 (2013) 11427–11433, https://doi.org/10. 1021/am403663 org/. M.R. Gao, Y.F. Xu, J. Jiang, S.H. Yu, Nanostructured metal chalcogenides: synthesis, modification, and applications in energy conversion and storage devices, Chem. Soc. Rev. 42 (2013) 2986–3017, https://doi.org/10.1039/c2cs35310e. Y. Liu, G. Jiang, Z. Huang, Q. Lu, B. Yu, U. Evariste, M. Pian Pian, Decoration of hollow mesoporous carbon spheres by NiCo2S4 nanoparticles as electrode materials for asymmetric supercapacitors, ACS Appl. Energy Mater. 2 (11) (2019) 8079–8089, https://doi.org/10.1021/acsaem.9b01569. Zoran Stević, Mirjana Rajčić Vujasinović, Milan Radunović, Estimation of parameters obtained by electrochemical impedance spectroscopy on systems containing high capacities, Sensors 9 (2009) 7365–7373, https://doi.org/10.3390/s90907365. Z. Stevic, M. Rajci, C. Vujasinovi, Chalcocite as a potential material for supercapacitors, J. Power Sources 160 (2006) 1511–1517, https://doi.org/10.1016/j. jpowsour.2006.03.014. P. Kumar, R. Nagarajan, An elegant room temperature procedure for the precise control of composition in the CuS system, Inorg. Chem. 50 (2011) 9204–9206, https://doi.org/10.1021/ic201133a org/. H.R. Ghenaatian, M.F. Mousavi, M.S. Rahmanifar, High performance hybrid supercapacitor based on two nanostructured conducting polymers: self-doped polyaniline and polypyrrole nano fibers, Electrochim. Acta 78 (2012) 212–222, https:// doi.org/10.1016/j.electacta.2012.05.139 org/. J. Wei, S. Xing, B. Yan, D. He, H. Suo, C. Zhao, A novel high-performance electrode: in-situ growth of copper sulfide film on copper foil for the application of supercapacitor, J. Mater. Sci. Mater. Electron 26 (2015) 4185–4192, https://doi.org/10. 1007/s10854-015-2964-9. Y. Zhang, J. Xu, Y. Zheng, X. Hu, Y. Shang, Y. Zhang, Interconnected CuS nanowalls with rough surfaces grown on nickel foam as high-performance electrodes for supercapacitors, RSC Adv. 6 (2016) 59976–59983, https://doi.org/10.1039/ C6RA10327H. A.M. Patil, A.C. Lokhande, N.R. Chodankar, P.A. Shinde, J.H. Kim, C.D. Lokhande, Interior design engineering of CuS architecture alteration with rise in reaction bath temperature for high performance symmetric flexible solid state supercapacitor, J. Ind. Eng. Chem. 46 (2017) 91–102, https://doi.org/10.1016/j.jiec.2016.10.019 doi:org/. Z. Tian, H. Dou, B. Zhang, W. Fan, X. Wang, Three-dimensional graphene combined with hierarchical CuS for the design of flexible solidstatesupercapacitorsElectrochim, Acta 237 (2017) 109–118, https://doi.org/10. 1016/j.electacta.2017.03.207 org/. W.M. Dose, M.J. Piernas-Muñoz, V.A. Maroni, S.E. Trask, I. Bloom, C.S. Johnson, Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries, Chem. Commun. 54 (2018) 3586–3589, https://doi.org/10.1039/c8cc00456k. S.P. Mundinamani, M.K. Rabinal, Molecular modification of highly degenerate semiconductor as an active electrode to enhance the performance of supercapacitors, Mater. Res. Express, vol 1 (2015) 45508, https://doi.org/10.1088/ 2053-1591/1/4/045508. C. Xiang, M. Li, M. Zhi, A. Manivannan, N. Wu, A reduced graphene oxide/Co3O4 composite for supercapacitor electrode, J Power Sources 226 (2013) 65–70, https://doi.org/10.1016/j.jpowsour.2012.10.064. L. Zhang, H. Gong, Improvement in flexibility and volumetric performance for
[37] [38] [39] [40] [41]
[42]
[43]
[44] [45]
[46]
[47] [48] [49] [50]
[51]
[52] [53] [54]
[55]
[56]
[57] [58]
[59] [60]
[61]
7
supercapacitor application and the effect of Ni–Fe ratio on electrode behaviour, J. Mater. Chem. A 3 (2015) 7607–7615, https://doi.org/10.1039/C4TA06649A. K.J. Huang, J.Z. Zhang, Y.L. Jia, K. Xing, Y.M. Liu, Acetylene black incorporated layered copper sulfide nanosheets for high-performance supercapacitor, J. Alloys Compd 641 (2015) 119–126, https://doi.org/10.1016/j.jallcom.2015.04.075 org/. R. Mulla, M.K. Rabinal, Ambient growth of highly oriented Cu2S dendrites of superior thermoelectric behaviour, Appl. Surf. Sci. 397 (2017) 70–76, https://doi. org/10.1016/j.apsusc.2016.11.106 doi.org/doi. M.N. Kalasad, M.K. Rabinal, B.G. Mulimani, Facile synthesis of bioconjugated fluorescent CDS nanoparticles of tunable light emission, J. Phys. D. Appl. Phys. 43 (2010), https://doi.org/10.1088/0022-3727/43/30/305301. S.D. Giri, A. Sarkar, Electrochemical study of bulk and monolayer copper in alkaline solution, J Electrochem Soc 163 (3) (2016) H252–H259, https://doi.org/10.1149/ 2.0071605jes. S.R. Das, S.B. Majumder, R.S. Katiyar, Kinetic analysis of the Li+ ion intercalation behavior of solution derived nano-crystalline lithium manganate thin films, J. Power Sources 139 (2005) 261–268, https://doi.org/10.1016/j.jpowsour.2004.06. 056. Xiaoyi Hou, Xianming Liu, Yang Lu, Jinbing Cheng, Rongjie Luo, Qiuhong Yu1, Xinli Wei1, Hailong Yan, Xiaoxu Ji, Jang-Kyo Kim, Yongsong Luo, Copper sulfide nanoneedles on CNT backbone composite electrodes for high-performance supercapacitors and Li-S batteries, J. Solid State Electrochem. 21 (2017) 349–359, https://doi.org/10.1007/s10008-016-3322-4. G. Wu1, P. Tan, D. Wang, Z. Li, L. Peng, Y. Hu, C. Wang, W. Zhu, S. Chen, W. Chen, High-performance supercapacitors based on electrochemical-induced verticalaligned carbon nanotubes and polyaniline nanocomposite electrodes, Sci. Rep. 7 (43676) (2017), https://doi.org/10.1038/srep43676. W.M. Dose, M.J. Piernas-Muñoz, V.A. Maroni, S.E. Trask, I. Bloom, C.S. Johnson, Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries, Chem. Commun 54 (2018) 3586–3589, https://doi.org/10.1039/c8cc00456k. I.S. Ike, I. Sigalasab, S. Iyuke, Understanding performance limitation and suppression of leakage current or self-discharge in electrochemical capacitors: a review, RSC, Phys. Chem. Chem. Phys. 18 (2016) 661, https://doi.org/10.1039/ C5CP05459A. H.R. Ghenaatian, M.F. Mousavi, M.S. Rahmanifar, High performance hybrid supercapacitor based on two nanostructured conducting polymers: self-doped polyaniline and polypyrrole nano fibers electrochim, Acta 78 (2012) 212–222, https:// doi.org/10.1016/j.electacta.2012.05.139 doi:org/. J. Guo, X. Zhang, Y. Sun, X. Zhang, L. Tang, X. Zhang, Double-shell cus nanocages as advanced supercapacitor electrode materials, J Power Sources 355 (2017) 31–35, https://doi.org/10.1016/j.jpowsour.2017.04.052. D. Ranjith Kumar, S. Kesavan, M.L. Baynosa, J.J. Shim, Flower-like Cu1.8S nanostructures for high-performance flexible solid-state supercapacitors, Appl. Surf. Sci. 448 (2018) 547–558, https://doi.org/10.1016/j.apsusc.2018.03.247 doi:org/. A. Allagui, A.S. Elwakil, M.E. Fouda, A.G. Radwan, Capacitive behavior and stored energy in supercapacitors at power line frequenciesJ, Power Sources 390 (2018) 142–147, https://doi.org/10.1016/j.jpowsour.2018.04.035 doi.org/. Y. Wang, F. Liu, Y. Ji, M. Yang, W. Liu, W. Wang, Q. Sun, Z. Zhang, X. Zhao, X. Liu, Controllable synthesis of various kinds of copper sulfides (CuS, Cu7S4, Cu9S5) for high-performance supercapacitors, Dalton Trans 44 (2015) 10431–10437, https:// doi.org/10.1039/C5DT00402K. I.K. Durga, S.S. Rao, A.E. Reddy, C.V.V.M. Gopi, H.-J. Kim, Achieving copper sulfide leaf like nanostructure electrode for high performance supercapacitor and quantum-dot sensitized solar cells, Appl Surf Sci 435 (2018) 666–675, https://doi. org/10.1016/j.apsusc.2017.11.171. H. Zhao, L. Liu, R. Vellacheri, Y. Lei, Recent advances in designing and fabricating, self-supported nanoelectrodes for supercapacitors, Adv. Sci (2017) 1700188, , https://doi.org/10.1002/advs.201700188. W. Razaa, F. Alib, N. Razac, Y. Luoa, K.-H. Kimf, J.Y.S. Kumare, A. Mehmooda, E.K. Eilhann, Recent advancements in supercapacitor technology, Nano Energy 52 (2018) 441–473, https://doi.org/10.1016/j.nanoen.2018.08.013. Wenbin Fu, Weihua Han, Heming Zha, Junfeng Mei, Yunxia Li, Zemin Zhang, Erqing Xie, Nanostructured cus networks composed of interconnected nanoparticles for asymmetric supercapacitors, Phys. Chem. Chem. Phys 18 (2016) 24471–24476, https://doi.org/10.1039/c6cp02228f. W. Xiao, W. Zhou, T. Feng, Y. Zhang, H. Liu, H. Yu, Liangliang Tian Yong Pu, OnePot solvothermal synthesis of flower-like copper sulfide/ reduced graphene oxide composite superstructures as high performance supercapacitor electrode materials, J. Mater. Sci. 28 (2017) 5931–5940, https://doi.org/10.1007/s10854-016-6267-6. S. Peng, L.F. b, C. Wei, X. Liu, H. Zhang, W. Xu, J. Xu, Flexible polypyrrole/copper sulfide/bacterial cellulose nanofibrous composite membranes as supercapacitor electrodes, Carbohydr Polym. 157 (2017) 344–352, https://doi.org/10.1016/j. carbpol.2016.10.004. Bibekananda De, Tapas Kuila, Nam Hoon Kim, Joong Hee Lee, Carbon dot stabilized copper sulphide nanoparticles decorated graphene oxide hydrogel for high performance asymmetric supercapacitor, doi: 10.1016/j.carbon.2017.06.076, (2017). S. Podili1, D. Geetha1, P.S. Ramesh, One-pot synthesis of CTAB stabilized mesoporous cobalt doped CuS nano flower with enhanced pseudocapacitive behaviour, J. Mater. Sci: Mater Electron 28 (2017) 15387–15397, https://doi.org/10.1007/ s10854-017-7424-2. Y.-K. Hsu, Y.-C. Chen, Y.-G. Lin, Synthesis of copper sulfide nanowire arrays for high-performance supercapacitors, Electrochim. Acta 139 (2014) 401–407, https:// doi.org/10.1016/j.electacta.2014.06.138. K.-J. Huang, J.-Z. Zhang, Ke xing one-step synthesis of layered CuS/multi-walled carbon nanotube, nanocomposites for supercapacitor electrode material with ultrahigh specific capacitance, Electrochim. Acta 149 (2014) 28–33, https://doi.org/ 10.1016/j.electacta.2014.10.079. P. Xua, C. Miaoa, K. Chenga, K. Yea, J. Yina, D. Caoa, Z. Pana, G. Wanga, X. Zhang, High electrochemical energy storage performance of controllable synthesis of nanorod Cu1.92S accompanying nanoribbon CuS directly grown on copper foam,
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal Electrochim. Acta 214 (2016) 276–285, https://doi.org/10.1016/j.electacta.2016. 08.049. [62] K. Zhou, J. Liang, J. Liu, P. Sun, J. Bu, W. Zhang, G. Chen, Synthesis of porous Cu7.2S4 sub-microspheres by an ion exchange method for high-performance supercapacitors, RSC Adv. 6 (2016) 16832–16837, https://doi.org/10.1039/ C5RA26976H. [63] Kun Wang, Chongjun Zhao, Zhuomin Zhang, Shudi Min, Xiuzhen Qian, A facile onestep route to synthesize the three layer nanostructure of CuS/RGO/Ni3S2 and its high electrochemical performance, RSC Adv 6 (2016) 16963–16971. [64] Y. Lu, X. Liu, W. Wang, J. Cheng, H. Yan, C. Tang, J.-K. Kim4, Y. Luo, Hierarchical, porous CuS microspheres integrated with carbon nanotubes for highperformance
supercapacitors, Sci Rep 5 (2015) 16584, https://doi.org/10.1038/srep16584. [65] Y.-W. Lee, B.-S. Kim, J. Hong, a J. Lee, a S. Pak, H.-S. Jang, D. Whang, S.N. Cha, J.I. Sohn, J.M. Kim, A pseudo-capacitive chalcogenide-based electrode with dense 1-dimensional nanoarrays for enhanced energy density in asymmetric supercapacitors, J. Mater. Chem. A 4 (2016) 10084–10090, https://doi.org/10.1039/ C6TA03337G. [66] Y. Jun Yang, Facile preparation of CuS-coated multiwalled carbon nanotubes for supercapacitor application: a study on the effect of electrolyte, fullerenes, nanotubes and carbon nanostructur fullerenes, Nanotubes Carbon Nanostruct. 25 (8) (2017) 497–503, https://doi.org/10.1080/1536383X.2017.1344836.
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Rapid ambient growth of copper sulfide microstructures: Binder free electrodes for supercapacitor Sajeeda Shaikh, M.K. Rabinal
T
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Department of Physics, Karnatak University Dharwad, Karnatak 580003, India
ARTICLE INFO
ABSTRACT
Keywords: Copper sulfide films Supercapacitor Specific capacitance Specific energy Specific power
Metal chalcogenides are earth abundant, low cost, and less toxic materials with a good electrochemical activity and hence can be ideal materials for high performance supercapacitors. Here the copper sulfide is successfully deposited on copper foil by a rapid and ambient chemical route to form highly oriented and uniform microstructures. These films are adherent with a high surface area and porosity and also electrically conducting, hence can be used as binder free electrodes for supercapacitors. These devices were constituted with KOH as an electrolyte, which show a good electrochemical performances; specific capacitance 1173 Fg−1 at 1 mVs−1, specific energy 301.4 Whkg−1, and specific power 1400 Wkg−1 with a good cyclability. Hence, the proposed technique is simple and cost effective to form high performance supercapacitors.
1. Introduction The World's energy crisis is the result of limited utilization of alternative energy resources. The conventional energy resources, which contribute almost up to 80% of our energy demands are rapidly consumed due to industrial revolutions, population explosion and economic growth [1,2]. Such a huge consumption creates a high carbon emission that has severe negative impacts on health and the environment. Hence, over the last few decades, energy research is mainly focused on clean and greenways of energy generation and storage using renewable energy resources [3]. Among these resources, the solar energy is abundant, clean, regular and convertible in various ways. However, it is intermittent and poses several challenges associated with energy storage systems. At present, the energy storage/conversion through electrochemical methods is one of the interesting technologies, which includes mainly batteries and supercapacitors [4]. Supercapacitors are needed as sustainable and renewable power sources and have attracted a lot of attention due to their ultrafast charge/discharge capability, long cycle life, reversibility, high power density, moderate energy density, safe operation, and eco-benignity. Further, the complementation of batteries and supercapacitors helps to develop high energy density and high power density energy storage systems [5]. Electrochemical supercapacitors are b divided into two types one is the double layer capacitors (non-Faradaic) and another is pseudo-capacitors (Faradaic). Due to fast and fully reversible redox reactions, the latter exhibits a higher specific capacitance. The transition metal
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Chalcogenides, such as CuS, MoS2, CdSe, Ni3S4, etc. have been widely studied compounds as supercapacitor electrode materials [6]. A good electrode must possess a high surface area, controlled porosity, fast charge/discharge cycles, a high conductivity, chemically stable and cost-effective [7]. Presently the best known electrodes, which include RuOx, MnO2, MoS2, Fe3S2, Ni3S4, conducting polymers/composites, etc. do not meet all the criteria, further some of these materials require a complex method of syntheses [8–14]. Hence, it is highly desirable to develop the electrodes which are earth abundant and easy to make in on large scale at a lower cost. In this respect, thin films of various materials on a given substrate have become attractive options due to least series resistance that enhance the power density [15]. Besides, the electrodes must also have a high electrolyte accessible network, which accelerates the ion transport during the charging/discharging process with a good retention rate. Conventional electrodes are fabricated by casting slurry of electroactive material and binder on the current collector, the latter include certain organic materials, polymers, etc. [16]. Often, the binder severely affects the electrical conductivity and ion accessibility in active material [17]. Binder-free electrodes using solution phase synthesis are now at the peak of research, wherein a directly in-situ single-step growth of nano/micro-architectures on current collector provides a highly efficient electron high ways that may significantly enhance the rate capability of supercapacitors. Some of the current collectors such as carbon, stainless steel, titanium, copper, silicon, nickel, and their nano/micro structures are successfully used for the creation of binder-free electrodes [18]. Such electrodes promote
Corresponding author. E-mail address: [email protected] (M.K. Rabinal).
https://doi.org/10.1016/j.est.2020.101288 Received 19 December 2019; Received in revised form 4 February 2020; Accepted 12 February 2020 Available online 25 February 2020 2352-152X/ © 2020 Elsevier Ltd. All rights reserved.
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal
easy diffusion and transportation of ions which enhances the electrochemical performance. In this respect, the metal chalcogenides such as CuS (CuxS, x = 1–2), MoS2, Co9S8, NiS, Ni3S2, WS2, etc. have become attractive electrode materials [19–22]. Particularly the metal-sulfides due to better electrical conductivity, a large crystal unit cells, and low electronegativity and complex valence of sulfur, these compounds show an excellent electrochemical performance as compared to other metal sulfides/oxides [23,24]. Theoretically, it is predicted that copper sulfides may exhibits a high specific capacitance as compared to other metal sulfides [25–26]. It is known that CuxS (x = 1–2) exhibit a wide variety of metastable and mixed phases, in which the location of Cu atoms/ions in the close-packed ‘S’ lattice are not well identified, the position of these ions change with composition. The known CuxS metastable phases are: Villamanite (CuS2), Covellite, in the “sulfur-rich region”; and Yarrowite (Cu1.12S), Spinkopite (Cu1.39S), Gerite (Cu1.6S), Anilite (Cu1.75S), Digenite (Cu1.8S), Djurleite (Cu1.95S), Chalcocite (Cu2S), in the “copper-rich region”. Among these phases, Cu2S and Cu1.75S are considered to be more promising electrode materials [27–28]. There are current attempts to explore these materials for supercapacitor applications. Wei et al. proposed the growth of copper sulfide (CuS) microspheres directly on a copper foil via redox reaction between CuSO4 and Na2S2O3 that shows the specific capacitance of 1443 F-g−1at current density of 1 A-g−1 [29], Zhang et al. proposed the growth of copper sulfide nano-walls on nickel foam via hydrothermal method with a good electrochemical performance, demonstrating the specific capacitance close to 1124 F-g−1 at current density of 15 mAcm−2 with a good cyclability [30]. Further, the combination of CuxS phases with other nanostructures of carbon, conducting polymers and metal foams have shown a dramatic improvement in the values of specific capacitance [31]. However, the CuS phases suffer with certain drawbacks, like low intrinsic conductivity (~10−3 S-cm−1) as compared to other electrode materials such as carbons and conducting polymers, difficulty in phase pure synthesis, lack of schematic tuning of porosity for better electrochemical accessibility of ions, poor interfacial kinetics, the low stability due to irreversible volume change during electrochemical cycling, etc. [32]. Further, many of existing synthetic techniques on these materials are carried out at elevated temperatures [33]. Still, the novelties in (on) large scale, ambient, and low cost syntheses are highly desirable aspects. The present work is focussed to synthesize highly active copper sulfide on copper foil by a simple and quick reaction process just at ambient condition, which results into promising electrode material for supercapacitors.
sulfide. After the reaction, the foil is taken out and rinsed several times with deionized water and dried in an open atmosphere. It is observed that the thickness of film gradually increased with reaction time, but it losses adherence as it becomes thicker. Therefore the above procedure is standardized after a couple of trials. This reaction is carried out for different concentrations of sulfur and it is concluded that increased molarity of sulfur accelerates the reaction and resulting in the thicker films, hence the rate of reaction and film thickness increases with an increase in molarities from 0.01 M to 0.1 M. In the present work, the concentration and time are restricted to 0.03 M and 5 min, respectively, which results in highly adherent and uniform films. The mass of active material grown on the copper foil can be determined by taking the mass difference of copper foil before and after the growth of copper sulfide film with a suitable correction to the chemical composition. 3. Cell assembly and electrochemical measurements As prepared copper sulfide electrodes were used for electrochemical measurements by forming a symmetric capacitor. Typically 2 M aqueous KOH is used as an electrolyte and Watmann filter paper of 200 µm (thick) as a separator which is soaked in an electrolyte and sandwiched between the above electrodes. Cyclic voltammetry (CV), Galvanostatic charge/discharge (GCD), impedance measurements were carried out using electrochemical work station (CHI660E, CHI Instruments, USA). A supercapacitor is constituted using our homemade setup, the details of which are given elsewhere [34]. The room temperature cyclic voltametry measurements were carried out at various scan rates ranging from 1 mV-S−1 to 50 m-Vs−1 with a working potential window of (−1 to 0.8) V0. The quantitative specific capacitance is estimated from cyclic voltamograms using the following Eq. (1) [35–37].
CS =
1 × 2×S× V×m
vf
I dI
(1)
vi −1
where, Cs is the specific capacitance of the material (F-g ), I represents the current, ΔV, is the working potential window, m is an active mass of the active electrode materials (weight of both the electrodes), S is the scan rate, vi and vf are the initial and final voltages scanned window, respectively. Specific Capacitance is also estimated using discharge curve by Galvanostatic charge/discharge measurements. Here Cs is estimated using Eq. (2).
Cs =
2. Experimental details
I× t m× V
(2)
where I is the applied current, Δt is the discharge time, m is the total mass of active materials, and ΔV is the applied potential window. On the basis of mass of active electrode material the overall performance and efficiency of an electrode is determined through specific energy density (E (Wh- kg−1)) and specific power density (P (W-kg−1)) parameters, which can be calculated from the Eq. (3) and (4), respectively.
Commercial Copper foil (purity 99.99%), 0.17 mm thick (20 mm × 20 mm) is used as a source of copper and substrate, sulfur powder was obtained from sd-Fine chemicals, India, which is used as an elemental source for sulfurization, and hydrazine hydrate (NH2NH2.H2O) is obtained from Spectrochem, India. All the chemicals used in this work are of AR grade and are used as received without further purification. Deionized water is used throughout the work and all the syntheses were carried out at room temperature. In a typical synthesis, initially 0.03 M of 20 ml of sulfur solution is prepared by dissolving 1.9 mg of sulfur powder in 0.2 ml of hydrazine hydrate and further diluted by adding deionised water. A copper substrate of dimension (2 cm × 2 cm × 0.17 mm) is well cleaned using HCl and acetone to remove the surface oxide. The copper foil is horizontally immersed into the sulfur-hydrazine hydrate complex, at room temperature for 5 min to grow copper sulfide on copper foil. The reaction bath is placed at room temperature for 5 min. There is a rapid formation of the dark-gray film indicating the formation of copper
E = 0.5 × Cs × ( V )2 P=
E t
(3) (4)
4. Results and discussion The copper sulfide nano/microstructure grown on the copper foil is schematically represented in Fig. 1(a), which illustrates the synthetic procedure and indicates the simplicity of the present method. The copper foil is immersed in sulfur-hydrazine hydrate complex solution, immediately a dark gray film grows on the surface of copper. The
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Fig. 2. X-Ray diffraction pattern of as prepared copper sulfide.
of sulfur as well as coordinating agent to form the above complex, also it facilitates the reaction between copper and sulfur. The use of hydrazine hydrate-sulfur complex has been successfully utilized by our group for the past few years to synthesize highly oriented copper sulfide dendrites for thermoelectric and other applications [38], the details of which is given in our earlier reports. This route is also used in the synthesis of cadmium sulfide nanoparticles with tunable particle size [39]. It is expected that surface atoms on copper foil react with hydrazine hydrate complex to form copper sulfide. When the coordinated copper ions from the substrate react with the complex of sulfur ions initially a thin layer of copper sulfide is formed on the substrate, later the sulfur ions migrate and react with unreacted copper present below the sulfide film leading to inward growth of higher morphological structures. Prepared films are structurally porous, so it is expected that sulfur ions may reach unreacted copper even after the formation of copper sulfide film that results in a highly porous copper sulfide films of desired thickness. The photographic image of copper sulfide microstructures on copper substrate is shown in Fig. 1(b), which displays the good adherence and flexibility of these films, even with bending close to 360° it still remains in contact with foil. Hence, the present synthetic method provides a highly adherent copper sulfide electrode. Next, the crystal structure of as-grown film is studied by recording powder X-ray diffraction using Philips X'Pert powder diffractometer with CuKα radiation (λ = 1.54056 Å), a typical powder pattern is shown in Fig. 2, the peaks are well indexed with hexagonal Anilite (Cu1.75S) phase when compared with the standard data file (JCPDS: card no.33-0489). It matches with characteristic planes of (202), (220), (131), (100), (304), and (305) and all the peaks are quite sharp. This observation, clearly confirms that the as-prepared film is phase pure
Fig. 1. (a) A schematic representation of copper sulfide formation on a copper electrode, (b) A real image of copper sulfide film deposited on a copper plate.
probable chemical reaction can be as follows.
(5) and highly crystalline in nature. The surface morphology of these films is studied with a field emission scanning electron microscope (FESEM) (JEOL-JSM-6700F), with the acceleration voltage of 15 kV. The typical images are shown in Fig. 3(a) and (b) for bare copper and deposited
In this reaction process, the hydrazine hydrate reacts with sulfur to form sulfur-hydrazene hydrate complex. This complex is air stable and quite suitable for the synthesis of sulfur based nanoparticles by an aqueous route. Here, hydrazine hydrate works as a solvent for dilution 3
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Fig. 4. (a) Cyclic voltamograms of the copper sulfide electrode based supercapacitor at different scan rate in 2 M KOH solution, (b) The Specific capacitance measured at different scan rates.
to enhance the specific capacitance of supercapacitors. These peaks are caused by the redox reactions of copper sulfide surface species with an alkaline electrolyte and is directly related to the oxidation state of Cu at high concentration of electrolyte [40]; it can be seen from the figure that the cathodic and anodic peaks shift to lower and higher potentials with increase in scan rates, which is quite typical in kinematical process and is also referred as intercalation/deintercalation of the ions at the electrode-electrolyte interface where the peak current (ip) is linearly proportional to the square root of scan rate, commonly referred as the Radels-Sevick effect [41]. The area under curve increases with increase in scan rate and the redox peaks are still observed even at the higher scan rate of 50 mV s−1, which indicates that crystalline structures of copper sulfide are beneficial for fast reversible redox reactions with good electrolytic efficiency in KOH electrolyte. The Cs is calculated from these curves using Eq. (1) for different scan rates and the same has been shown in Fig. 4(b) which is a typical behavior for electrochemical supercapacitors. The specific capacitance of 1173 Fg−1 is obtained at 1 mVs−1, which decreases to 540 Fg−1 at the scan rate 50 mVs−1. The galvanostatic charge/discharge is used to estimate the electrochemical capacitance as well as the cyclability. The charge-discharge curves of these devices are plotted in Fig. 5(a), it is evident from the nonlinear behavior of charging/discharging curves the redox reactions do play an important role in these devices [42,43]. The specific capacitance is calculated from these charge-discharge curves, using Eq. (2). At different discharge currents, the specific capacitance is 1355 Fg−1, 1107 Fg−1, 973 Fg−1, 517 F g−1 at 2 Ag−1, 3 Ag−1, 5 Ag−1, 15 Ag−1 respectively, is much higher than the previously reported literature values on copper sulfide alone. As the current density increases the discharge time decreases, also the specific capacitance decreases with
Fig. 3. FESEM image of copper sulfide film (an inset shows a high magnification image view). (a) Bare Copper Foil, (b) Copper Foil with Copper sulfide deposition.
films of copper sulfide, respectively. Here the size and deposition of copper sulfide is quite uniform over the entire film area. The inset in the same figure is high resolution FESEM image of the same, which illustrates 3D-hexagonal morphology. Such large surface area forms due to thin mesoporous nanostructures resulting into more electroactive sites for faradic energy storage and it ensures good mechanical adhesion and electrical connectivity with a current collector. Further, the large crystalline structure of CuxS efficiently allows the electrolyte ions to access the active surface area. Such a simple chemical scheme that allows the easy formation of active materials on current collectors and avoids the use of polymer binders with enhanced porosity has a definite advantage. Besides this, the binders always lead to low electrical conductivity and put the adverse effect on electrode material with unnecessary dead mass. Next, the symmetric supercapacitors are constituted using these electrodes with KOH as an electrolyte, as mentioned above in the experimental section. Cyclic voltametry measurements were carried out and their results are shown in Fig. 4. These curves are recorded for different scan rates with a potential window of −1 V to 0.8 V, these curves are different from quasi rectangular nature that is typical in the case of electric double layer capacitors (EDLC). The as-prepared copper sulfide electrodes showed a multiple numbers of redox peaks, which are due to pseudocapacitance behavior, which is an essential requirement 4
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Fig. 6. Electrochemical impedance curve (Nyquist plot) for copper sulfide electrode based supercapacitor.
has been shown in Figure S1 as the supporting information. This clearly reveals that Cu1.75S can be a good electrode for electrochemical supercapacitors. The electronic conductivity and ionic diffusion at the interface between electrolyte and electrodes can be studied by electrochemical impedance spectroscopy (EIS). These measurements are carried out in the frequency range from 0.1 Hz to 1 MHz at a potential of 10 mV. The imaginary impedance (Zʹʹ) versus real impedance (Zʹ), that is referred as the Nyquist plot, is shown in Fig. 6, the equivalent circuit of the device and the computed z-fit for an open circuit potential with AC perturbation of 5 mV are also shown in the same figure as an inset [47]. There is a good fit between experimental data and the calculated curve. Further, these measurements show a partial semicircle at a high frequency and an inclined line at low frequency. The semicircle diameter at high-frequency equals to the charge transfer resistance (Rct) at the electrolyte-electrode interface and is also called as faraday resistance which is a limiting factor for the specific power of a supercapacitor which is attributed to the faradic reaction(s). From the diameter of the semicircle arc, the Rct can be estimated and it is 10 Ω, this clearly demonstrates that electrons have a better charge transfer property in these electrodes and hence a good pseudocapacitive behavior. The above magnitude of Rct is typically observed in the Cu1.75S based supercapacitors, it is in the range of 12.4 Ω to 15 Ω [48,49]. The x-intercept of the Nyquist plot corresponds to the equivalent series resistance (Rs) and it is estimated to be 2 Ω, which has various contributions like internal resistance of the electrode, ionic resistance of the electrolyte, and resistance of the interface between electrode and electrolyte. Hence, it has components of both ions and electrons. As mentioned earlier in the introduction the copper sulfide microstructures are seriously explored as electrode materials for energy storage applications, particularly for electrochemical supercapacitors. The copper sulfide exhibits close to nine phases, of which Cu2S and Cu1.75S are considered as better materials [50]. In general, the major work on copper sulfides as electrodes for supercapacitors has been summarized in the Table 1, where the parameters like synthesis method, morphology, and electrochemical performance are mentioned. There is limited work on pure copper sulfide as supercapacitor electrodes; such devices exhibit the typical specific capacitance in the range 250 F-g−1 to 400 F-g−1. A superior value of 1443 F-g−1 at 1 A-g−1 has been reported in the case of well structured microspheres of CuS on copper foil that was grown by chemical deposition for 18 h. However, the suitable combination of copper sulfide phases with other nanostructured materials such as carbon (QDs, CNTs, MWCNTs, r-GO, etc.), conducting
Fig. 5. (a) Galvanostatic charge/discharge curves of the copper sulfide electrodes at 2 Ag−1, 3 Ag−1 and 5 Ag−1, 15 Ag−1 in 2 M KOH electrolyte, (b) Stability performance curve, specific capacitance retention. Potential Vs Cycle Number.
an increase in current density, which concludes that ions of the electrolyte have insufficient time to diffuse into the active material. Further, the decrease in specific capacitance with increase current density is due to electrode resistance and insufficient Faradaic reaction at higher discharge current densities. Such a decrease in capacitance is also associated with a change in shape, loss of active surface area and alteration of resistance during charge/discharge processes [44,45]. A long cycling life is another important requirement, which depends on the stability of as-prepared electrode material. In this context, the cycling life test is carried out by performing galvanostatic charge/discharge measurements at a current density of 2 Ag−1 for more than 3000 cycles. Fig. 5(b) represents these stability test measurements, for clarity the data here is shown only for the first 1500 charge/discharge cycles, interestingly the specific capacitance stays stable and it goes from 100% to slightly down that is 99%, the values in between these cycles show distortion, this could be due to the formation of ion concentration gradient at the electrode/electrolyte boundary that eventually retards the diffusion of ions into the material [46]. The repeated C-V measurements of these devices with a large number of cycles showing a negligible change confirm that the material is stable. However, in order to check this, after complete characterization for more than 1500 cycles the Cu1.75S powder from the electrode surface was recovered and repeatedly washed with water to perform the XRD. It is observed that there is no noticeable change in the crystalline structure of as prepared and used material, which clearly shows that the material is stable, this 5
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Table 1 Summarizes the recent literature on the use of copper sulfide phases as an electrode material for supercapacitors along with their references. Sl No 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
Material CuS-nanoarrays @ Cu foil CuS-nanoarrays @ Cu mesh CuS-microspheres @ Cu foil CuS nanotubes –MWCNT @ carbon paper Cu7.2S4- microspheres @ Ni foam Cu1.92S-nanorods & CuS-nanoribbon @ Cu foam Cobalt doped CuS – nanoflowers @ glassy carbon electrode CuS-rGO- flower like @ Ni foam CuS –nano hollow spheres @ Ni foam CuS-nanowalls @ Ni- foam CuS-microspheres / CNT @ Ni foam Acetylene black/CuS- nanosheets @ Ni foam Carbon Dot/CuS/GO- Hydrogels @ stainless steel point cell CuS/rGO/Ni3S2 nanoarrays CuS-polypyrrole @ bacterial cellulose membrane CuS nanosheets- MWCNT @ Ni foam CuS- nanoflower @ Ni- foam
Method of synthesis wet-chemical synthesis at 80 °C Two step chemical synthesis Chemical deposition (18 h) Two step ion exchange Two step ion exchange Chemical etching method at 80°C Hydrothermal process at 130°C for 10 h Hydrothermal process at 180°C for 12 h Hydrothermal at 160°C for 24 hrs Hydrothermal at 80°C for 12 h Two step-ion exchange 160°C and 80°C Solvothermal synthesis Hydrothermal process at 180°C for 12 h Hydrothermal process @ 160°C 12 h Insitu oxidative polymerization & solvothemal process Hydrothermal process at 180°C for 72 h Solvothermal @ 80 °C
polymers, bacterial cellulose, and metal foams exhibit a superior specific capacitance that ranges from 300 F-g−1 to 2981 F-g−1. A significantly much higher value of 5029 F-g−1 at 4 A-g−1 has been also reported in the case of CuS-nanoflower on Ni- foam grown by a solvothermal route at 80 °C [51]. It is too high as compared to the best possible values that are reported for various advanced materials and hence it deserves further investigations. The best recent reported values of specific capacitance in the case of carbon, conducting polymers, metal oxides, and their composites are ⁓600 F-g−1, 3500 F-g−1, 4000 F-g−1, 2500 F-g−1 respectively [52,53]. Finally, the Cu1.92S is a suitable electrode material for supercapacitors. It is identified from the literature that smaller the value of charge transfer resistance and series resistance higher will be the power density of supercapacitors [54]. Since the as prepared Cu1.75S nano/ micro structured film has high porosity, the electrolyte ions are easily accessible to electrodes and thereby the charge transfer resistance is lowered. Based on the above electrochemical performance, the obtained Cu1.75S electrodes in this work are apparently superior to many of the previously reported copper sulfide based materials. Hence, the present results clearly suggest that Cu1.75S is a good electrode material to constitute supercapacitors. The present devices exhibit a high pseudo electrode capacity close to 1173 F-g−1, a better specific power 1400 WKg−1, specific energy 301 Whkg−1and excellent rate capability, which are important parameters of supercapacitors.
Performance −1
Refs. −2
305 F-g at 2 mA-cm 378.0 mF-cm−2 −1 at 1 A g−1 1443 F-g 636.28 F-g−1 at10 Ag−1 245.5 F-g−1 at 5 mVS−1 448 F-g−1 at 5 mA-cm−2 586.45 F-g−1 at 5 mV/S 368.3 F-g−1 at 1 Ag−1 948 F-g−1 at 1 A g−1 1124 F-g−1 at 15 mA-cm-2 1960 F-g−1 @ 10 mA-cm−2 2981 F-g−1 at1 Ag−1 920 F-g−1 at 1 Ag−1 1692.7 F-g−1 at 6.5 A g−1 580 F-g−1at 1 mA-cm−2 2800 F-g−1 at 1 Ag−1 5029 F-g−1 at 4 Ag−1
[59] [65] [29] [66] [62] [61] [58] [55] [18] [30] [64] [37] [57] [63] [56] [60] [51]
Methodology, Validation, Writing - original draft, Writing - review & editing. Declaration of Competing Interest None. Acknowledgments One of the authors Miss Sajeeda Shaikh gratefully acknowledges the fellowship support under DST- Purse Phase-II programmes, New Delhi, Govt. of India. Supplementary materials Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.est.2020.101288. References [1] F. Wang, X. Wu, X. Yuan, a Zaichun Liu, Y. Zhang, L. Fu, Y. Zhu, Q. Zhou, Y. Wu, Wei Huang, Latest advances in supercapacitors: from new electrode materials to novel device designs, Chem. Soc. Rev. 46 (2017) 6816–6854, https://doi.org/10. 1039/c7cs00205j. [2] .. M.Sevilla, R. Mokaya, Energy storage applications of activated carbons: supercapacitors and hydrogen storage, Energy Environ. 7 (2014) 1250–1280, https://doi. org/10.1039/c3ee43525c. [3] H. Zhao, L. Liu, R. Vellacheri, Y. Lei, Recent advances in designing and fabricating self-supported nanoelectrodes for supercapacitors, Adv.Sci. 4 (2017), https://doi. org/10.1002/advs.201700188. [4] E. Talaie, P. Bonnick, X. Sun, Q. Pang, X. Liang, L.F. Nazar, Methods and protocols for electrochemical energy storage materials research, Chem. Mate (2017) 90–105, https://doi.org/10.1021/acs.chemmater.6b02726. [5] C.J. Hung, P. Lin, T.Y. Tseng, High energy density asymmetric pseudocapacitors fabricated by graphene/carbon nanotube/MnO2 plus carbon nanotubes nanocomposites electrode, J. Power Sources 259 (2014) 145–153, https://doi.org/10. 1016/j.jpowsour.2014.02.094. [6] B.K. Kim, S. Sy, A. Yu, J. Zhang, Handb. electrochemical supercapacitors for energy storage and conversion, Clean. Energy Syst. (2014) 1–25, https://doi.org/10.1002/ 9781118991978.hces112. [7] Yongkun Liu, Guohua Jiang, Zheng Huang, Qiuling Lu, Bo Yu, Uwamahoro Evariste, and Pian Pian M., Decoration of hollow mesoporous carbon spheres by NiCo2S4 nanoparticles as electrode materials for asymmetric supercapacitors, ACS applied Energy Material, doi: 10.1021/acsaem.9b01569. [8] H. Kwon, D. Hong, I. Ryu, S. Yim, Supercapacitive properties of 3D-Arrayed polyaniline hollow nanospheres encaging ruo2 nanoparticles, ACS Appl. Mater. Interfaces 9 (2017) 7412–7423, https://doi.org/10.1021/acsami.6b14331. [9] S. Sun, G. Jiang, Y. Liu, Y. Zhang, J. Zhou, B. Xu, Growth of MnO2 nano particles on hybrid carbon nano fibers for flexible symmetrical supercapacitors, Mater. Lett 197 (2017) 35–37, https://doi.org/10.1016/j.matlet.2017.03.092 doi.org/. [10] S. Palsaniya, H.B. Nemade, A.K. Dasmahapatra, Synthesis of polyaniline/graphene/ MoS2 nanocomposite for high performance supercapacitor electrode, Polymer (Guildf) 150 (2018), https://doi.org/10.1016/j.polymer.2018.07.018. [11] S.P. Guo, J.C. Li, J.R. Xiao, H.G. Xue, Fe3S4 nanoparticles wrapped in an rGO matrix for promising energy storage: outstanding cyclic and rate performance, ACS
5. Conclusions Herein a simple room temperature binder free chemical route has been developed to form highly adherent, hydrophilic nano/microstructures of Cu1.75S on a copper plate as an electrode material for supercapacitor. These devices are constituted using above electrodes with KOH as an electrolyte; these exhibit an excellent supercapacitive performance, giving specific capacitance 1173 F-g−1 at 1 mV-s−1 and excellent rate capability close to 99% and good cycle life. The superior electrochemical behavior has been attributed to the interconnected network of Cu1.75S, which provides efficient transport pathways for both electrons and electrolytic ions during the charge/discharge processes of these devices. Eventually, this leads to superior current capacitive behavior and better cycling performance. The work is simple, cost-effective and easily scalable techniques to form binder-free copper sulfide for electrochemical energy storage applications. CRediT authorship contribution statement Sajeeda Shaikh: Data curation, Software, Writing - original draft, Writing - review & editing. M.K. Rabinal: Conceptualization, 6
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[12]
[13] [14]
[15]
[16] [17] [18] [19]
[20] [21]
[22]
[23] [24]
[25] [26] [27] [28]
[29]
[30]
[31]
[32]
[33] [34]
[35] [36]
Appl. Mater. Interfaces 9 (2017) 37694–37701, https://doi.org/10.1021/acsami. 7b10406. H. Wang, M. Liang, D. Duan, W. Shi, Y. Song, Z. Sun, Rose-like Ni3S4 as batterytype electrode for hybrid supercapacitor with excellent charge storage performance, Chem. Eng. J. 350 (2018) 523–533, https://doi.org/10.1016/j.cej.2018.05.004 doi. org/. S. Sun, G. Jiang, Y. Liu, B. Yu, U. Evariste, Preparation of α-MnO2/Ag/RGO hybrid films for asymmetric supercapacitor, J. Energy Storage 18 (2018) 256–258, https:// doi.org/10.1016/j.est.2018.05.010. B. Yu, G. Jiang, W. Xu, C. Cao, Y. Liu, N. Lei, U. Evariste, P. Ma, Construction of NiMoO4/CoMoO4 nanorod arrays wrapped by Ni-Co-S nanosheets on carbon cloth as high performance electrode for supercapacitor, J Alloys Compd 799 (2019) 415–424. Dan Feng, Yingying Lv, Zhangxiong Wu, Yuqian Dou, Lu Han, Zhenkun Sun, Yongyao Xia, Gengfeng Zheng, Dongyuan Zhao, Free-Standing mesoporous carbon thin films with highly ordered pore architectures for nano devices, J. Am. Chem. Soc 133 (2011) 15148–15156, https://doi.org/10.1021/ja2056227 doi.org/. B. Song, F. Wu, Y. Zhu, Z. Hou, K. sik Moon, C.P. Wong, Effect of polymer binders on graphene-based free-standing electrodes for supercapacitors electrochim, Acta 267 (2018) 213–221, https://doi.org/10.1016/j.electacta.2018.02.072 org/. C. Yuan, J. Li, L. Hou, X. Zhang, L. Shen, X.W. Lou, Ultrathin mesoporous NiCo2O4 nanosheets supported on ni foam as advanced electrodes for supercapacitors, Adv. Funct. Mater 22 (2012) 4592–4597, https://doi.org/10.1002/adfm.201200994. H. Heydari, S.E. Moosavifard, S. Elyasi, M. Shahraki, Nanoporous CuS nano-hollow spheres as advanced material for high-performance supercapacitors, Appl. Surf. Sci. 394 (2017) 425–430, https://doi.org/10.1016/j.apsusc.2016.10.138 org/. Muhammad Sufyan Javed, Shuge Dai, Mingjun Wang, Donglin Guo, Lin Chen, Xue Wang, Chenguo Hu, Yi X., J.solid state flexible supercapacitor based on molybdenum sulfide hierarchical nanospheresPower sources, 285, (2015) 63–69, doi:org/10.1016/j.jpowsour.2015.03.079. H. Li, Y. Gao, Y. Shao, Y. Su, X. Wang, Vapor-Phase atomic layer deposition of Co9S8 and its application for supercapacitors, Nano Lett 15 (2015) 6689–6695, https://doi.org/10.1021/acs.nanolett.5b02508. Xiaoyan Yan, Xili Tong, Lei Ma, Yuming Tian, Yuesheng Cai, Changwei Gong, Mingang Zhang, Liping Liang, Synthesis of porous NiS nanoflake arrays by ion exchange reaction from NiO and their high performance supercapacitor properties, Mater. Lett 124 (2014) 133–136, https://doi.org/10.1016/j.matlet.2014.03.067 org/. S. Ratha, C.S. Rout, Supercapacitor electrodes based on layered tungsten disulfidereduced graphene oxide hybrids synthesized by a facile hydrothermal method, ACS Appl. Mater. Interfaces 5 (2013) 11427–11433, https://doi.org/10. 1021/am403663 org/. M.R. Gao, Y.F. Xu, J. Jiang, S.H. Yu, Nanostructured metal chalcogenides: synthesis, modification, and applications in energy conversion and storage devices, Chem. Soc. Rev. 42 (2013) 2986–3017, https://doi.org/10.1039/c2cs35310e. Y. Liu, G. Jiang, Z. Huang, Q. Lu, B. Yu, U. Evariste, M. Pian Pian, Decoration of hollow mesoporous carbon spheres by NiCo2S4 nanoparticles as electrode materials for asymmetric supercapacitors, ACS Appl. Energy Mater. 2 (11) (2019) 8079–8089, https://doi.org/10.1021/acsaem.9b01569. Zoran Stević, Mirjana Rajčić Vujasinović, Milan Radunović, Estimation of parameters obtained by electrochemical impedance spectroscopy on systems containing high capacities, Sensors 9 (2009) 7365–7373, https://doi.org/10.3390/s90907365. Z. Stevic, M. Rajci, C. Vujasinovi, Chalcocite as a potential material for supercapacitors, J. Power Sources 160 (2006) 1511–1517, https://doi.org/10.1016/j. jpowsour.2006.03.014. P. Kumar, R. Nagarajan, An elegant room temperature procedure for the precise control of composition in the CuS system, Inorg. Chem. 50 (2011) 9204–9206, https://doi.org/10.1021/ic201133a org/. H.R. Ghenaatian, M.F. Mousavi, M.S. Rahmanifar, High performance hybrid supercapacitor based on two nanostructured conducting polymers: self-doped polyaniline and polypyrrole nano fibers, Electrochim. Acta 78 (2012) 212–222, https:// doi.org/10.1016/j.electacta.2012.05.139 org/. J. Wei, S. Xing, B. Yan, D. He, H. Suo, C. Zhao, A novel high-performance electrode: in-situ growth of copper sulfide film on copper foil for the application of supercapacitor, J. Mater. Sci. Mater. Electron 26 (2015) 4185–4192, https://doi.org/10. 1007/s10854-015-2964-9. Y. Zhang, J. Xu, Y. Zheng, X. Hu, Y. Shang, Y. Zhang, Interconnected CuS nanowalls with rough surfaces grown on nickel foam as high-performance electrodes for supercapacitors, RSC Adv. 6 (2016) 59976–59983, https://doi.org/10.1039/ C6RA10327H. A.M. Patil, A.C. Lokhande, N.R. Chodankar, P.A. Shinde, J.H. Kim, C.D. Lokhande, Interior design engineering of CuS architecture alteration with rise in reaction bath temperature for high performance symmetric flexible solid state supercapacitor, J. Ind. Eng. Chem. 46 (2017) 91–102, https://doi.org/10.1016/j.jiec.2016.10.019 doi:org/. Z. Tian, H. Dou, B. Zhang, W. Fan, X. Wang, Three-dimensional graphene combined with hierarchical CuS for the design of flexible solidstatesupercapacitorsElectrochim, Acta 237 (2017) 109–118, https://doi.org/10. 1016/j.electacta.2017.03.207 org/. W.M. Dose, M.J. Piernas-Muñoz, V.A. Maroni, S.E. Trask, I. Bloom, C.S. Johnson, Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries, Chem. Commun. 54 (2018) 3586–3589, https://doi.org/10.1039/c8cc00456k. S.P. Mundinamani, M.K. Rabinal, Molecular modification of highly degenerate semiconductor as an active electrode to enhance the performance of supercapacitors, Mater. Res. Express, vol 1 (2015) 45508, https://doi.org/10.1088/ 2053-1591/1/4/045508. C. Xiang, M. Li, M. Zhi, A. Manivannan, N. Wu, A reduced graphene oxide/Co3O4 composite for supercapacitor electrode, J Power Sources 226 (2013) 65–70, https://doi.org/10.1016/j.jpowsour.2012.10.064. L. Zhang, H. Gong, Improvement in flexibility and volumetric performance for
[37] [38] [39] [40] [41]
[42]
[43]
[44] [45]
[46]
[47] [48] [49] [50]
[51]
[52] [53] [54]
[55]
[56]
[57] [58]
[59] [60]
[61]
7
supercapacitor application and the effect of Ni–Fe ratio on electrode behaviour, J. Mater. Chem. A 3 (2015) 7607–7615, https://doi.org/10.1039/C4TA06649A. K.J. Huang, J.Z. Zhang, Y.L. Jia, K. Xing, Y.M. Liu, Acetylene black incorporated layered copper sulfide nanosheets for high-performance supercapacitor, J. Alloys Compd 641 (2015) 119–126, https://doi.org/10.1016/j.jallcom.2015.04.075 org/. R. Mulla, M.K. Rabinal, Ambient growth of highly oriented Cu2S dendrites of superior thermoelectric behaviour, Appl. Surf. Sci. 397 (2017) 70–76, https://doi. org/10.1016/j.apsusc.2016.11.106 doi.org/doi. M.N. Kalasad, M.K. Rabinal, B.G. Mulimani, Facile synthesis of bioconjugated fluorescent CDS nanoparticles of tunable light emission, J. Phys. D. Appl. Phys. 43 (2010), https://doi.org/10.1088/0022-3727/43/30/305301. S.D. Giri, A. Sarkar, Electrochemical study of bulk and monolayer copper in alkaline solution, J Electrochem Soc 163 (3) (2016) H252–H259, https://doi.org/10.1149/ 2.0071605jes. S.R. Das, S.B. Majumder, R.S. Katiyar, Kinetic analysis of the Li+ ion intercalation behavior of solution derived nano-crystalline lithium manganate thin films, J. Power Sources 139 (2005) 261–268, https://doi.org/10.1016/j.jpowsour.2004.06. 056. Xiaoyi Hou, Xianming Liu, Yang Lu, Jinbing Cheng, Rongjie Luo, Qiuhong Yu1, Xinli Wei1, Hailong Yan, Xiaoxu Ji, Jang-Kyo Kim, Yongsong Luo, Copper sulfide nanoneedles on CNT backbone composite electrodes for high-performance supercapacitors and Li-S batteries, J. Solid State Electrochem. 21 (2017) 349–359, https://doi.org/10.1007/s10008-016-3322-4. G. Wu1, P. Tan, D. Wang, Z. Li, L. Peng, Y. Hu, C. Wang, W. Zhu, S. Chen, W. Chen, High-performance supercapacitors based on electrochemical-induced verticalaligned carbon nanotubes and polyaniline nanocomposite electrodes, Sci. Rep. 7 (43676) (2017), https://doi.org/10.1038/srep43676. W.M. Dose, M.J. Piernas-Muñoz, V.A. Maroni, S.E. Trask, I. Bloom, C.S. Johnson, Capacity fade in high energy silicon-graphite electrodes for lithium-ion batteries, Chem. Commun 54 (2018) 3586–3589, https://doi.org/10.1039/c8cc00456k. I.S. Ike, I. Sigalasab, S. Iyuke, Understanding performance limitation and suppression of leakage current or self-discharge in electrochemical capacitors: a review, RSC, Phys. Chem. Chem. Phys. 18 (2016) 661, https://doi.org/10.1039/ C5CP05459A. H.R. Ghenaatian, M.F. Mousavi, M.S. Rahmanifar, High performance hybrid supercapacitor based on two nanostructured conducting polymers: self-doped polyaniline and polypyrrole nano fibers electrochim, Acta 78 (2012) 212–222, https:// doi.org/10.1016/j.electacta.2012.05.139 doi:org/. J. Guo, X. Zhang, Y. Sun, X. Zhang, L. Tang, X. Zhang, Double-shell cus nanocages as advanced supercapacitor electrode materials, J Power Sources 355 (2017) 31–35, https://doi.org/10.1016/j.jpowsour.2017.04.052. D. Ranjith Kumar, S. Kesavan, M.L. Baynosa, J.J. Shim, Flower-like Cu1.8S nanostructures for high-performance flexible solid-state supercapacitors, Appl. Surf. Sci. 448 (2018) 547–558, https://doi.org/10.1016/j.apsusc.2018.03.247 doi:org/. A. Allagui, A.S. Elwakil, M.E. Fouda, A.G. Radwan, Capacitive behavior and stored energy in supercapacitors at power line frequenciesJ, Power Sources 390 (2018) 142–147, https://doi.org/10.1016/j.jpowsour.2018.04.035 doi.org/. Y. Wang, F. Liu, Y. Ji, M. Yang, W. Liu, W. Wang, Q. Sun, Z. Zhang, X. Zhao, X. Liu, Controllable synthesis of various kinds of copper sulfides (CuS, Cu7S4, Cu9S5) for high-performance supercapacitors, Dalton Trans 44 (2015) 10431–10437, https:// doi.org/10.1039/C5DT00402K. I.K. Durga, S.S. Rao, A.E. Reddy, C.V.V.M. Gopi, H.-J. Kim, Achieving copper sulfide leaf like nanostructure electrode for high performance supercapacitor and quantum-dot sensitized solar cells, Appl Surf Sci 435 (2018) 666–675, https://doi. org/10.1016/j.apsusc.2017.11.171. H. Zhao, L. Liu, R. Vellacheri, Y. Lei, Recent advances in designing and fabricating, self-supported nanoelectrodes for supercapacitors, Adv. Sci (2017) 1700188, , https://doi.org/10.1002/advs.201700188. W. Razaa, F. Alib, N. Razac, Y. Luoa, K.-H. Kimf, J.Y.S. Kumare, A. Mehmooda, E.K. Eilhann, Recent advancements in supercapacitor technology, Nano Energy 52 (2018) 441–473, https://doi.org/10.1016/j.nanoen.2018.08.013. Wenbin Fu, Weihua Han, Heming Zha, Junfeng Mei, Yunxia Li, Zemin Zhang, Erqing Xie, Nanostructured cus networks composed of interconnected nanoparticles for asymmetric supercapacitors, Phys. Chem. Chem. Phys 18 (2016) 24471–24476, https://doi.org/10.1039/c6cp02228f. W. Xiao, W. Zhou, T. Feng, Y. Zhang, H. Liu, H. Yu, Liangliang Tian Yong Pu, OnePot solvothermal synthesis of flower-like copper sulfide/ reduced graphene oxide composite superstructures as high performance supercapacitor electrode materials, J. Mater. Sci. 28 (2017) 5931–5940, https://doi.org/10.1007/s10854-016-6267-6. S. Peng, L.F. b, C. Wei, X. Liu, H. Zhang, W. Xu, J. Xu, Flexible polypyrrole/copper sulfide/bacterial cellulose nanofibrous composite membranes as supercapacitor electrodes, Carbohydr Polym. 157 (2017) 344–352, https://doi.org/10.1016/j. carbpol.2016.10.004. Bibekananda De, Tapas Kuila, Nam Hoon Kim, Joong Hee Lee, Carbon dot stabilized copper sulphide nanoparticles decorated graphene oxide hydrogel for high performance asymmetric supercapacitor, doi: 10.1016/j.carbon.2017.06.076, (2017). S. Podili1, D. Geetha1, P.S. Ramesh, One-pot synthesis of CTAB stabilized mesoporous cobalt doped CuS nano flower with enhanced pseudocapacitive behaviour, J. Mater. Sci: Mater Electron 28 (2017) 15387–15397, https://doi.org/10.1007/ s10854-017-7424-2. Y.-K. Hsu, Y.-C. Chen, Y.-G. Lin, Synthesis of copper sulfide nanowire arrays for high-performance supercapacitors, Electrochim. Acta 139 (2014) 401–407, https:// doi.org/10.1016/j.electacta.2014.06.138. K.-J. Huang, J.-Z. Zhang, Ke xing one-step synthesis of layered CuS/multi-walled carbon nanotube, nanocomposites for supercapacitor electrode material with ultrahigh specific capacitance, Electrochim. Acta 149 (2014) 28–33, https://doi.org/ 10.1016/j.electacta.2014.10.079. P. Xua, C. Miaoa, K. Chenga, K. Yea, J. Yina, D. Caoa, Z. Pana, G. Wanga, X. Zhang, High electrochemical energy storage performance of controllable synthesis of nanorod Cu1.92S accompanying nanoribbon CuS directly grown on copper foam,
Journal of Energy Storage 28 (2020) 101288
S. Shaikh and M.K. Rabinal Electrochim. Acta 214 (2016) 276–285, https://doi.org/10.1016/j.electacta.2016. 08.049. [62] K. Zhou, J. Liang, J. Liu, P. Sun, J. Bu, W. Zhang, G. Chen, Synthesis of porous Cu7.2S4 sub-microspheres by an ion exchange method for high-performance supercapacitors, RSC Adv. 6 (2016) 16832–16837, https://doi.org/10.1039/ C5RA26976H. [63] Kun Wang, Chongjun Zhao, Zhuomin Zhang, Shudi Min, Xiuzhen Qian, A facile onestep route to synthesize the three layer nanostructure of CuS/RGO/Ni3S2 and its high electrochemical performance, RSC Adv 6 (2016) 16963–16971. [64] Y. Lu, X. Liu, W. Wang, J. Cheng, H. Yan, C. Tang, J.-K. Kim4, Y. Luo, Hierarchical, porous CuS microspheres integrated with carbon nanotubes for highperformance
supercapacitors, Sci Rep 5 (2015) 16584, https://doi.org/10.1038/srep16584. [65] Y.-W. Lee, B.-S. Kim, J. Hong, a J. Lee, a S. Pak, H.-S. Jang, D. Whang, S.N. Cha, J.I. Sohn, J.M. Kim, A pseudo-capacitive chalcogenide-based electrode with dense 1-dimensional nanoarrays for enhanced energy density in asymmetric supercapacitors, J. Mater. Chem. A 4 (2016) 10084–10090, https://doi.org/10.1039/ C6TA03337G. [66] Y. Jun Yang, Facile preparation of CuS-coated multiwalled carbon nanotubes for supercapacitor application: a study on the effect of electrolyte, fullerenes, nanotubes and carbon nanostructur fullerenes, Nanotubes Carbon Nanostruct. 25 (8) (2017) 497–503, https://doi.org/10.1080/1536383X.2017.1344836.
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