Nickel Cobalt Sulfide Research Articles

Rapid and controllable microwave synthesis of nickel cobalt sulfide electrodes for high-performance asymmetric supercapacitors

The efficient and controllable synthesis method of high-performance energy storage electrode materials is crucial for advancing the development of energy storage technologies. Herein, by leveraging microwave heating technology in the sulfidation of nickel cobalt MOF, we effectively enhanced the efficiency of the synthesis process. Notably, sulfidation time emerged as a pivotal factor in tuning the crystalline phase structure and conductive properties of the material, leading to the successful development of NCS2 electrode material with a unique structure through optimized sulfidation conditions. Electrochemical performance tests of the NCS2 material revealed exceptional results; it exhibited a specific capacity of 1311 Fg[Formula: see text] at a current density of 1 Ag[Formula: see text] and retained 73.4% of its initial capacity when the current density increased to 10 Ag[Formula: see text], demonstrating outstanding rate performance. The composite NCS2//AC supercapacitor exhibits an energy density of 24.2 Whkg[Formula: see text] at power density of 800 Wkg[Formula: see text], even though after 1000 consecutive charge-discharge cycles, the capacity retention rate remained high at 77.1%, validating the exceptional stability and reliability of the NCS2 material during cycling. This work employs microwave sulfidation for the rapid and controlled synthesis of nickel cobalt sulfides, providing a green and efficient synthetic strategy for metal sulfide active materials.

Yolk@shell layered NiCo hydroxide: Controllable synthesis, sulfuration and electrochemical applications for hybrid supercapacitors

Developing electrode materials with rational structures is an important strategy for constructing high-performance hybrid supercapacitors (HSCs). Herein, designing a yolk@shell structure composed of layered nickel-cobalt hydroxide with a Ni/Co feed ratio of 4:1 (denoted as layered Ni4Co1 hydroxide) and nickel-cobalt sulfide with a sulfuration duration of 2 h (labeled as Ni4Co1S-2h) to enhance the capacity and stabilize the cyclic performances of HSCs was conducted. The yolk@shell structured microspheres of layered Ni4Co1 hydroxide were synthesized using a cetyltriethylammonium bromide (CTAB) template-assisted solvothermal treatment. Subsequently, nickel-cobalt sulfide microspheres with the unique yolk@shell structure were prepared from layered Ni4Co1 hydroxide precursor. Notably, yolk@shell Ni4Co1S-2h microspheres feature a large specific surface area and an interspace between the yolk and shell, facilitating charge transfer but also effectively alleviating volume expansion during ion transport and electron transfer. The resultant Ni4Co1S-2h material demonstrates a superior capacity of 902.2 C·g−1 at 3·A g−1, while the assembled Ni4Co1S-2h//porous carbon (PC) HSC shows a relatively higher energy density (83.1 Wh·kg−1) and power density (15000 W·kg−1). The design of yolk@shell structured layered Ni4Co1 hydroxide and Ni4Co1S-2h electrode materials holds significant implications for the advancement of high-performance HSCs.

Synergistic effect of SGO/Nickel cobalt sulfide nanocomposite on Ni-foam for supercapacitor performance with widened potential windows − A microwave-assisted synthesis

Designing of high-performance supercapacitors with superior energy storage capabilities is crucial for addressing the growing demand for sustainable energy solutions. In this study, we investigate the synergistic effect of a sulfonated graphene oxide (SGO) /nickel-cobalt sulfide (NiCoS) nanocomposite on Ni-foam for supercapacitor applications. The SGO/NiCoS nanocomposite exhibits improved electrochemical performance, including increased specific capacitance, enhanced rate capability, and widened operating potential windows. The material exhibits a high energy density of 117.76 Wh/kg and a power density of 503.24 W/kg. The ASC also showed superior electrochemical stability, retaining 90 % of its coulombic efficiency after 10,000 cycles. The combination of NiCoS and SGO on Ni-foam significantly augments energy and power density, making it an attractive material for advanced supercapacitors. The microwave-assisted synthesis technique employed in this study enables rapid and uniform heating, reducing reaction times and improving selectivity. This work demonstrates the potential of SGO/ NiCoS nanocomposites on Ni-foam for supercapacitors, highlighting the benefits of synergistic material combinations and efficient synthesis methods.

Bimetallic nickel-cobalt sulfide grown on graphene foam for high-performance asymmetric supercapacitor

Although bimetallic nickel-cobalt sulfides (Ni/Co-S) have shown promising candidates as pseudocapacitive materials with excellent electrochemical performance, achieving high energy density, high power density, and good cyclability of Ni/Co-S electrode remains a challenge. In this study, the graphene foam (GF) with a three-dimensional (3D) skeleton was successfully prepared using a chemical vapor deposition (CVD) method. Subsequently, Ni/Co-S was in situ grown on the GF through a two-step hydrothermal method. A series of Ni/Co-S@GF-x (x=1, 2, 3) electrodes were prepared and optimized for electrochemical performance by regulating the molar ratio of Ni/Co salt precursors (3:1, 4:1, 5:1). The abundant pore structure of Ni/Co-S@GF not only facilitates ion migration, but also provides numerous electrochemical redox active sites for reactions. When utilized as electrodes in supercapacitors, the Ni/Co-S@GF-2 with a Ni/Co salt’s molar ratio of 4:1 displays a specific capacity of 4.68 C cm−2 at 1 mA cm−2. Furthermore, an asymmetric supercapacitor (ASC) was assembled using the optimal Ni/Co-S@GF-2 as cathode and Walnut shell-derived porous carbon as anode to evaluate the actual energy storage characteristics of the device. The ASC delivers a high power density of 822.86 mW cm−2 at an energy density of 32.0 mWh cm−2. This work presents a promising approach for designing and preparing nickel-cobalt sulfides for application in flexible energy storage devices.

Se-doped cobalt-nickel sulfide hollow nanospheres with heterostructure and engineered defects as high-performance electrode for supercapacitors

Porous structures with heterogeneous interfaces and defects are an important way to enhance electrochemically active sites and facilitate electron transfer, while also improving the permeability of the electrolyte and the rate of ion transport. In this study, Se-doped cobalt-nickel sulfide (Se-CoNi2S4) hollow nanospheres with heterostructure and defects were prepared from CoNi metal-organic framework (MOF) as substrate by sequential sulfidation and selenization treatments. Notably, the hollow structure not only offers additional ion transport channels to promote rapid transfer of ions in the electrolyte but also provides an increased number of electrochemically active sites. The morphology and electrochemical performance of Se-CoNi2S4 nanospheres with different levels of Se doping were compared. From the results, Se doping not only enhances the conductivity of CoNi2S4 but also increases its charge storage capacity. As an electrode material, the synthesized Se-CoNi2S4 composite that was synthesized demonstrated a notable specific capacitance of 1260 F g−1 at 1 A g−1. Additionally, when Se-CoNi2S4 was utilized as the anode and activated carbon served as the cathode in an asymmetric supercapacitor, it achieved an energy density of 44.6 Wh kg−1 at a power density of 827 W kg−1. After undergoing 10,000 cycles, this device demonstrated exceptional cycling stability, retaining 80.2 % of its initial capacitance. Therefore, the synthesized electrode material Se-CoNi2S4 has significant potential for energy storage applications.

Trade-Off between Degradation Efficiency and Recyclability: Zeolite-Enhanced Ni3-xCoxS4 Catalyst for Photocatalytic Degradation of Methylene Blue.

We herein report successful syntheses of both nickel cobalt sulfide (NCS) and its composite with zeolite (NCS@Z) using a solvothermal method. Techniques such as EDX analysis, SEM, and molar ratio determination were used for product characterization. The incorporation of NCS significantly changed the surface roughness and active sites of the zeolite, improving the efficiency of methylene blue degradation and its reusability, especially under UV irradiation. In comparing the pseudo-first order rates, the highest degradation efficiency of methylene blue was achieved with NCS-2@Z, having a degradation extent of 91.07% under UV irradiation. This environmentally friendly approach offers a promising solution for the remediation of methylene blue contamination in various industries.

Efficient Hydrogen and Oxygen Evolution: Dual-Functional Electrocatalyst of Zinc Iron Layered Double Hydroxides and Nickel Cobalt Sulfides on Nickel Foam for Seawater Splitting

Efficient Hydrogen and Oxygen Evolution: Dual-Functional Electrocatalyst of Zinc Iron Layered Double Hydroxides and Nickel Cobalt Sulfides on Nickel Foam for Seawater Splitting

Interface Engineering of Transition Metal-Based Heterostructure Electrocatalysts for Enhanced Hydrogen Evolution Reaction

Electrochemical water splitting to produce clean hydrogen plays a significant role in the development of the hydrogen economy. The rational design of highly efficient and inexpensive electrocatalysts is critical for improving water electrolysis efficiency. Herein, we report the fabrication of heterostructure monometallic, bimetallic, and trimetallic sulfides on Ni foam (NF) as porous self-supported electrodes for hydrogen evolution reaction (HER) via an energy-saving electrodeposition process. Molybdenum-cobalt-nickel sulfide electrode (MoCoNiS@NF) only requires a low overpotential of 114 mV to produce a current density of 10 mA cm-2 for HER, compared with nickel sulfides (NiS@NF, 142 mV) and cobalt-nickel sulfides (CoNiS@NF, 129 mV). The desirable HER performance of MoCoNiS@NF results from the synergistic effect of heterostructure interfaces of multi-metal sulfides, providing high intrinsic catalytic activity and a large amount of catalytic active sites. Electrochemical impedance spectroscopy and Tafel slope analysis proved the fast reaction kinetics of MoCoNiS@NF toward HER. Our present work provides valuable insights into the working mechanisms behind the HER catalytic process and new perspectives for the future design of cost-effective electrocatalysts for HER.

Enhanced electrochemical performance of nickel cobalt sulfide microspheres for high energy symmetric supercapacitors

Herein, Nickel cobalt sulfide (NCS) microspheres are successfully synthesized by an easy one-step hydrothermal method at different reaction conditions. The as-synthesized samples are used as electrode material to demonstrate their practical application for supercapacitors (SCs). Various techniques including X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Scanning electron microscopy (SEM), Energydispersive X-ray (EDX) spectroscopy are used for structural and morphological characterization of the synthesized materials which confirmed the successful formation of NCS. The electrochemical performance of prepared samples is tested using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The optimized NCSW-200 sample delivered a remarkable specific capacitance of 369 F g−1 at 0.5 A g−1. The energy and power density exhibited by NCSW-200 sample are as high as 32.8 Wh kg−1 and 266.6 W kg−1, respectively. After 2000 consecutive charge/discharge cycles, capacitance retention of 67% is achieved, depicting better cyclic stability. To illustrate the practical feasibility of the prepared symmetric cells of the optimized sample NCSW-200, a lab scale setup of three SC cells connected in series is fabricated and tested using a red light emitting diode (LED). The SC setup is able to illuminate a red LED for 2.5 minutes. The electrochemical performance demonstrated by NCS microspheres suggests its viable application as supercapacitor electrodes.

Synergistic Effects in BFO@NiCoS@CNT//AC Nanocomposite for High-Capacity Energy Storage Systems

Here, we synthesized a nanocomposite electrode material for high-performance asymmetric supercapacitor devices (ASCD) made of bismuth ferrite (BFO) nanocomposite and nickel cobalt sulfide with carbon nanotubes (NiCoS@CNT). To fabricate the BFO@NiCoS@CNT nanocomposite, a simple hydrothermal process was used. Electrochemical impedance spectroscopy, galvanostatic charge/discharge measurements, and cyclic voltammetry were used to evaluate the electrochemical experiments. At a scan speed of 5 mVs−1, the BFO@NiCoS@CNT nanocomposite exhibited a specific capacitance of 2890 Fg−1, surpassing pure BFO@NiCoS. Furthermore, the nanocomposite displayed excellent cyclic stability, retaining around 87.8% of its capacity retention even after 5000 cycles. Another notable property is its energy density (Ed) of 71 Whkg−1 at the power density (Pd) of 2400 Wkg−1. Based on these promising findings, BFO@NiCoS@CNT nanocomposite might be used to fabricate electrodes for high-performance hybrid supercapacitors. Our research indicates that this is the first report of a BFO@NiCoS@CNT nanocomposite used as an asymmetric supercapacitor.

Flexible Hybrid Supercapacitor Achieving 2.2V with NiCo2S4/Polyaniline/MnO2 and N, S-Co-Doped Carbon Nanofibers for Ultra-High Energy Density.

Flexible all-solid-state asymmetric supercapacitors (FAASC) represent a highly promising power sources for wearable electronics. However, their energy density is relatively less as compared to the conventional batteries. Herein, a novel ultra-high energy density FAASC is developed using nickel-cobalt sulfide (NiCo2S4)/polyaniline (PANI)/manganese dioxide (MnO2) ternary composite on carbon fiber felt (CF) as positive and N, S-co-doped carbon nanofibers (CNF)/CF as negative electrode, respectively. Initially, porous δ-MnO2 nanoworm-like network is decorated on CF using potentiodynamic method. Subsequently, interconnected PANI nanostructures is grown on the MnO2 via a facile in situ chemical polymerization, followed by the electrodeposition of highly porous NiCo2S4 nanowalls. Benefiting from 3D porous structure of conductive CF and redox active properties of NiCo2S4, PANI and MnO2, FAASC achieved a superior energy storage capacity. Later, high-performance N, S-co-doped CNF/CF negative electrode is synthesized using electropolymerization of PANI nanofibers on CF, followed by the carbonization process. The assembled FAASC exhibits a wide voltage window of 2.2V and remarkable specific capacitance of 143 F g-1 at a current density of 1 A g-1. The cell further delivers a superb energy density of 71.6Wh kg-1 at a power density of 492.7W kg-1, supreme cycle life and remarkable electrochemical stability under mechanical bending.

Engineering interfacial sulfur migration in transition-metal sulfide enables low overpotential for durable hydrogen evolution in seawater

Hydrogen production from seawater remains challenging due to the deactivation of the hydrogen evolution reaction (HER) electrode under high current density. To overcome the activity-stability trade-offs in transition-metal sulfides, we propose a strategy to engineer sulfur migration by constructing a nickel-cobalt sulfides heterostructure with nitrogen-doped carbon shell encapsulation (CN@NiCoS) electrocatalyst. State-of-the-art ex situ/in situ characterizations and density functional theory calculations reveal the restructuring of the CN@NiCoS interface, clearly identifying dynamic sulfur migration. The NiCoS heterostructure stimulates sulfur migration by creating sulfur vacancies at the Ni3S2-Co9S8 heterointerface, while the migrated sulfur atoms are subsequently captured by the CN shell via strong C-S bond, preventing sulfide dissolution into alkaline electrolyte. Remarkably, the dynamically formed sulfur-doped CN shell and sulfur vacancies pairing sites significantly enhances HER activity by altering the d-band center near Fermi level, resulting in a low overpotential of 4.6 and 8 mV at 10 mA cm−2 in alkaline freshwater and seawater media, and long-term stability up to 1000 h. This work thus provides a guidance for the design of high-performance HER electrocatalyst by engineering interfacial atomic migration.

A flexible, binder-free electrodes using nickel-cobalt sulfur modified carbon nanofibers for asymmetric supercapacitor applications

The development of high-performance energy storage devices using cost-effective sources are highly important for various applications. Herein, a simple electrodeposition route has been developed for the uniform decoration of nickel-cobalt sulfide (NiCoS) over the carbon nanofibers (CNF). The fabricated NiCoS/CNF has been used as positive electrode with Fe2O3/rGO/CNF as negative electrode to assemble asymmetric supercapacitor (ASC) device. The fabricated ASC device exhibited a good electrochemical performance including high specific capacitance (70 F g-1), excellent cyclic stability (86 % after 10,000 cycles), and good energy density (56.33 Wh kg-1 at 1200 W kg-1). The present simple synthesis process holds a great potential for the design of energy storage devices in various usages.

Photo-rechargeable asymmetric supercapacitors based on nickel–cobalt sulfide on titania as novel photo-active electrodes

Photo-supercapacitors (PSCs), which are environmentally benign devices for direct conversion and storage of solar energy into electricity, have a high potential for eliminating the requirement for grid electricity for a sustainable future. In this research, nickel sulfide (NS), cobalt sulfide (CS) and nickel cobalt sulfide (NCS) deposited on TiO2 nanotubes (TNT) have been prepared as novel photoactive electrodes for photorechargeable supercapacitors. X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), High-resolution transmission electron microscopy (HRTEM), Energy-dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Ultraviolet–visible spectroscopy (UV–Vis) were used to characterize the phase, morphology, elemental composition, oxidation states and optical properties of the films produced. Based on the photoelectrochemical measurements, the NCS@TNT-1 samples showed higher capability to produce and separate photogenerated charges compared to bare TNTs, NS@TNT and CS@TNT. The highest capacity of up to 471.6 mF/cm2 (at 0.7 mA/cm2) was shown by the NCS@TNT-1 electrode, which is about 11 times higher than that of bare TNTs (44 mF/cm2). In addition, the specific capacitance of the NCS@TNT-1 electrode (as the best sample) increased approximately twofold, reaching 955.6 mF/cm2 upon light illumination. Three photochargeable asymmetric supercapacitors were fabricated with NCS@TNT as the electrode and PVA-KOH as the electrolyte and separator. The specific capacitance of the fabricated supercapacitor increased by 1.57 times when illuminated by light. The device showed outstanding stability over 10,000 galvanostatic charge and discharge cycles with a capacity retention of 87 % and 94 % in the dark and under light conditions, respectively. More importantly, the illumination resulted in an extended discharge time.

Nanostructured binary transition-metal-sulfides and nanocomposites as high-performance electrodes for hybrid supercapacitors

Supercapacitors (SCs) are attractive as promising energy storage devices because of their distinctive attributes, such as high power density, good current charge/discharge ability, excellent cyclic stability, reasonable safety, and low cost. Electrode materials play key roles in achieving excellent performance of these SCs. Among them, binary transition metal sulfides (BTMSs) have received significant attention, attributed to their high conductivity, abundant active sites, and excellent electrochemical properties. This topic review aims to summarize recent advances in principles, design, and evaluation of the electrochemical performance for nanostructured BTMSs (including nickel–cobalt sulfides, zinc–cobalt sulfides, and copper–cobalt sulfides.) and their nanocomposites (including those carbon nanomaterials, transition metal oxides, binary transition metal oxides, transition metal sulfides, and polymers). Nanostructuring of these BTMSs and nanocomposites as well as their effects on the performance were discussed, including nanoparticles, nanospheres, nanosheets, nanowires, nanorods, nanotubes, nanoarrays, and hierarchitectured nanostructures. Their electrochemical performance has further been reviewed including specific capacitance, conductivity, rate capability, and cycling stability. In addition, the performance of hybrid supercapacitors (HSCs) assembled using the nanostructured BTMSs as the cathodes also have been summarized and compared. Finally, challenges and further prospects in the HSCs-based BTMS electrodes are presented.

In situ electrodeposited Zn-doped CoNiS as an efficient and stable electrocatalyst for overall water splitting in neutral media

Zinc-doped cobalt nickel sulfides coupled with polypyrrole hollow nanospheres grown on carbon paper (Zn-CoNiS/PHS/CP) were developed by unipolar pulse electrodeposition (UPED) method as efficient and stable electrocatalysts for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting in neutral media for the first time. With abundant active sites intrigued by moderate Zn doping, the optimized Zn10-CoNiS delivers improved catalytic performance with small overpotentials of 213 mV and 414 mV to achieve the current densities of 10 mA cm−2 for HER and OER respectively, and outstanding long-term stability. The water electrolyzer device with Zn10-CoNiS as both anode and cathode delivers a current density of 10 mA cm−2 at a cell voltage of 1.896 V in neutral media. The low charge transfer resistance of Zn-CoNiS and confinement effect of 2D Ni9S8/Co9S8 nanosheets on 0D ZnS nanodots endow the bifunctional electrocatalysts with efficient activity and high stability, providing a competitive candidate for green hydrogen production.

A highly stable membrane-free potentiometric pH sensor with nickel cobalt sulfide as the solid contact layer and ion recognition

In this work, a new NiCo2S4 based H+ ion-selective electrode (ISE) without a polymer membrane was proposed and used to rapidly monitor the pH values of wetland soils in the Yellow River Delta in China. This NiCo2S4-based potentiometric pH sensor without an ion-selective membrane (ISM) exhibited a near-Nernstian response slope (50.9 ± 0.4 mV/dec) and good sensitivity. Furthermore, the developed pH sensors using NiCo2S4 as a solid contact (SC) layer present good reproducibility and the standard deviation of Eo is only 0.75 mV (n = 6). The water layer at the SC/ISM interface of the NiCo2S4-based membrane-free potentiometric pH sensor vanished, thus yielding excellent long-term potential stability (8.6 ± 0.4 μV/h over 264 h). This pH sensor offers a new design strategy for the construction of miniaturized highly stable ISEs without ISM.

Synthesis of Flower-like Crystal Nickel–Cobalt Sulfide and Its Supercapacitor Performance

In order to improve the pseudocapacitance performance of metal sulfide electrode materials and obtain supercapacitor energy storage devices with excellent electrochemical reversibility and long-term cycle stability, the synthesis of flower-shaped crystal nickel–cobalt sulfide and its supercapacitor performance were studied. NiCo2S4 flower-shaped crystal nickel–cobalt sulfide was prepared by the hydrothermal method with nickel foam as the raw material, and electrode materials were added to prepare supercapacitor electrodes for testing of the supercapacitor performance. The physical properties of flower-shaped crystal nickel–cobalt sulfide were tested by a scanning electron microscope and transmission electron microscope, and the voltammetric cycle and constant current charge and discharge of supercapacitor electrodes prepared from this sulfide were analyzed through experiments. The experimental results showed that the flower crystal microstructure had a positive effect on the electrochemical properties. The capacitance value was always high at different current densities, and the capacity was as high as 3867.8 A/g at pH 12. After 2000 voltage–charge–discharge cycle tests, the petal-like sulfide capacity still had a retention rate of 90.57, the flower crystal nickel–cobalt sulfide still showed an excellent supercapacitor performance and the specific capacity was still high, which demonstrates that this sulfide has excellent cyclic stability and durability in electrochemical applications.

Fabrication of nickel-cobalt sulfide heterostructures with stable thermodynamic interfaces and enhanced electrochemical performance

Transition metal sulfides (TMS) with multicomponent heterostructure have been widely used as electrodes in electrochemical energy storage devices due to their abundant electroactive sites and fast charge transfer across the interfaces. Different kinds of heterostructures with specific TMS are fabricated by various routes to date, but it is still poorly understood how specific thermodynamic interfaces can be designed and easily coupled. Herein, the spinel and cobalt-pentlandite crystal phases of nickel–cobalt sulfides were chosen as models to demonstrate the formation of epitaxial heterointerface. The density functional theory calculations revealed the easy combination and high compatibility of these two crystal phases at the (111) plane. Along this guideline, a novel NiCo2S4/[Ni, Co]9S8 heterostructure was synthesized by a facile one-step hydrothermal strategy, with nanosheet-like shapes and well-defined heterointerfaces along the [111] crystal direction. The formation mechanism of the epitaxial heterointerface was proposed through the combination of solid and liquid phase reaction fields. As a proof-of-concept application, the obtained NiCo2S4/[Ni, Co]9S8 heterostructure as redox electrode for supercapacitor exhibits an enhanced specific capacitance of 1780F g−1 at 1 A/g and high capacitance retention of 70 % at 20 A/g. Moreover, the assembled aqueous hybrid supercapacitor of NiCo2S4/[Ni, Co]9S8//activated carbon delivers a high energy density of 62.8 Wh kg−1 at 0.4 kW kg−1 and excellent electrochemical stability after 3000 cycles. This work provides a new perspective on the epitaxial design of nickel–cobalt sulfide heterostructure with good lattice match as a promising electrode in energy storage devices.

Synthesis, Fabrication, and Performance Evaluation of Nickel-Cobalt Sulfide Nanostructures for Enhancing Energy Density of Supercapacitors in Energy Storage Applications

Synthesis, Fabrication, and Performance Evaluation of Nickel-Cobalt Sulfide Nanostructures for Enhancing Energy Density of Supercapacitors in Energy Storage Applications