A high-performance supercapacitor electrode material based on NiS/Ni 3 S 4 composite

Construction of thickness-controllable bimetallic sulfides/reduced graphene oxide as a binder-free positive electrode for hybrid supercapacitors

Devices for electrochemical energy storage with exceptional capacitance and rate performance, outstanding energy density, simple fabrication, long-term stability, and remarkable reversibility have always been in high demand. Herein, a high-performance binder-free electrode (3D NiCuS/rGO) was fabricated as a supercapacitor by a simple electrodeposition process on a Ni foam (NF) surface. The thickness of the deposited materials on the NF surface was adjusted by applying a low cycle number of cyclic voltammetry (5 cycles) which produced a thin layer and thus enabled the easier penetration of electrolytes to promote electron and charge transfer. The NiCuS was anchored by graphene layers producing nicely integrated materials leading to a higher electroconductivity and a larger surface area electrode. The as-fabricated electrode displayed a high specific capacitance (2211.029 F g-1 at 5 mV s-1). The NiCuS/rGO/NF//active carbon device can achieve a stable voltage window of 1.5 V with a highly specific capacitance of 84.3 F g-1 at a current density of 1 A g-1. At a power density of 749 W kg-1, a satisfactory energy density of 26.3 W h kg-1 was achieved, with outstanding coulombic efficiency of 100% and an admirable life span of 96.2% after 10 000 GCD cycles suggesting the significant potential of the as-prepared materials for practical supercapacitors.

Recent advances in synthesis, structural properties, and regulation of nickel sulfide-based heterostructures for environmental water remediation: an insight review

Heterostructured nanomaterials exhibit pronounced potential in environmental science, including the water purification, pollutant monitoring, and environmental remediation. Especially, their application through advanced oxidation processes has been found capable and adaptable in waste water treatment. In semiconductor photocatalysts, metal sulfides are the leading materials. However, for further modifications, the progresses on specific materials need to be overviewed. Among metal sulfides, nickel sulfides are the emerging semiconductors due to relatively narrow band gaps, high thermal and chemical stability, and cost effectiveness. The aim of the present review is to conduct a thorough analysis and summary of recent progress in the application of nickel sulfide-based heterostructures in water decontamination. Initially, the review introduces the emerging needs of the materials for environment following the characteristics features of metal sulfides with emphasis on nickel sulfides. Subsequently, synthesis strategies and structural properties of nickel sulfide (NiS and NiS₂)-based photocatalysts are discussed. Herein, controlled synthesis procedures to influence their active structure, compositions, shape, and size for the enhanced photocatalytic performances are also considered. Furthermore, there is discussion on heterostructures formed by metal modification, metal oxides, and carbon hybridized nanocomposites. In the continuation, the modified characteristics are investigated which favors the photocatalytic processes for degradation of organic contaminations in water. The overall study highlights significant improvements in degradation efficiency of hetero-interfaced NiS and NiS₂ photocatalysts towards organics that are comparable to expensive noble-metal photocatalysts. Finally, we also added a little on prospects for future advancement of nickel sulfide-based photocatalysts for applications in sustainable environmental remediation.

Review of NiS-Based Electrode Nanomaterials for Supercapacitors

As a new type of energy storage device, supercapacitors have the advantages of high-power densities, high safety factors, and low maintenance costs, so they have attracted widespread attention among researchers. However, a major problem with supercapacitors is that their energy densities are not high enough, which limits their application. Therefore, it is crucial to expand the application scenarios of supercapacitors to increase their energy density as much as possible without diminishing their advantages. The classification and working principles of supercapacitors are introduced in this paper. The electrochemical properties of pure NiS materials, NiS composites with carbon materials, NiS composites with sulfide materials, and NiS composites with transition metal oxides for supercapacitors are summarized. This paper may assist in the design of new electrode materials for NiS-based supercapacitors.

RGO nanosheet wrapped β-phase NiCu2S nanorods for advanced supercapacitor applications

A new integration strategy of transition metal sulfide with carbon-based materials is used to boost its catalytic property and electrochemical performances in supercapacitor application. Herein, crystalline reduced graphene oxide (rGO) wrapped ternary metal sulfide nanorod composites with different rGO ratios are synthesized using hydrothermal technique and are compared for their physical, chemical, and electrochemical performances. It is found that their properties are tuned by the weight ratios of rGO. The electrochemical investigations reveal that β-NiCu₂S/rGO nanocomposite electrode with 0.15 wt.% of rGO is found to possess maximum specific capacitance of 1583 F g^-1 at current density of 15 mA g^-1 in aqueous electrolyte medium. The same electrode shows excellent cycling stability with capacitance retention of 89% after 5000 charging/discharging cycles. The reproducibility test performed on NiCu₂S/rGO nanocomposite electrode with 0.15 wt.% of rGO indicates that it has high reproducible capacitive response and rate capability. Thus, the present work demonstrates that the β-NiCu₂S/rGO nanocomposite can serve as a potential electrode material for developing supercapacitor energy storage system.

NiS2 nanoparticles by the NaCl-assisted less-liquid reaction system for the magnesium-ion battery cathode

Rechargeable magnesium batteries are expected to be the next generation of energy storage devices. Therefore, it is of great significance to develop low-cost and long-life magnesium (Mg) electrode materials. However, the traditional method of synthesizing electrode materials is complicated, and it is difficult to remove potentially dangerous impurities. In this study, without adding any additional solvent, the crystal water in the reactant provides a liquid environment directly for the reaction, such that the whole reaction could be carried out safely and efficiently in the less liquid reaction system. Furthermore, NiS₂ in the cotton-like form was synthesized under the spatial effect of NaCl solution in a confined space. The fabricated material was tightly connected and has abundant active sites, which promote the rapid transport of charge. This work provides a general strategy of preparation methods for metal sulfides and also points in a new direction for the improvement of electrochemical performance with less-liquid reaction systems without additional solvents.

Flexible nickel disulfide nanoparticles-anchored carbon nanofiber hybrid mat as a flexible binder-free cathode for solid-state asymmetric supercapacitors

Nickel disulfide nanoparticles (NiS₂NPs)-anchored carbon nanofibers (NiS₂NPs@CNF) hybrid mats were fabricated via the sequential process of stabilization and carbonization of electrospun polyacrylonitrile-based fibers followed by hydrothermal growth of NiS₂NPs on the porous surface of CNFs. The vertical growth of NiS₂NPs on entire surfaces of porous CNFs appeared in the SEM images of hybrid mat. The hierarchical NiS₂NPs@CNF core-shell hybrid nanofibers with 3D interconnected network architecture can endow continuous channels for easy and rapid ionic diffusion to access the electroactive NiS₂NPs. The conductive and interconnected CNF core could facilitate electron transfer to the NiS₂shell. Moreover, the porous CNF as a buffering matrix can resist volumetric deformation during the long-term charge-discharge process. The NiS₂NPs@CNF electrode can yield high specific capacitance (916.3 F g^-1at 0.5 A g^-1) and reveal excellent cycling performances. The solid-state asymmetric supercapacitor (ASC) was fabricated with NiS₂NPs@CNF mat as a binder-free positive electrode and activated carbon cloth as a negative electrode. As-assembled ASC not only produce high specific capacitance (364.8 F g^-1at 0.5 A g^-1) but also exhibit excellent cycling stability (∼92.8% after 5000 cycles). The ASC delivered a remarkably high energy density of 129.7 Wh kg^-1at a power density of 610 W kg^-1. These encouraging results could make this NiS₂NPs@CNF hybrid mat a good choice of cathode material for the fabrication of flexible solid-state ASC for various flexible/wearable electronics.

Coordination agent-dominated phase control of nickel sulfide for high-performance hybrid supercapacitor

The property of an active material is not only influenced by its morphology and size, but also by its crystal phase. The present phase regulation of nickel sulfide is mainly achieved by controlling the participation of sulfur source in reaction. Thus, new perspectives direct at phase control need to be explored and supplemented. Herein, we proposed a novel coordination agent-dominated phase modulation strategy assisted by a hydrothermal process. It is found that increasing the amount of coordination agent can drove the phase transformation from the initial composite of β-NiS/α-NiS/Ni₃S₄ to β-NiS/α-NiS, and then to pure β-NiS. The mechanism of phase regulation has been proposed, and the general application of this method has been demonstrated. By employing coordination agent, the size of resulted products is reduced, and the morphology is optimized. As a result, all of the pure β-NiS electrodes indicate significantly enhanced specific capacity than the pristine β-NiS/α-NiS/Ni₃S₄ composite. Notably, the sample synthesized with 3 mmol of urea (S11) shows uniform morphology and smallest size, and it gives a highest specific capacity of 223.8 mAh g^-1 at 1 A g^-1, almost 1.5 times of the original sample. The fabricated S11//rGO device delivers a high energy density of 56.6 Wh·kg^-1 at a power density of 407.5 W·kg^-1, and keeps an impressive capacity retention of 84% after 20,000 cycles. This work put forwards a new prospect for controlling the phase and composition of nickel sulfide based on coordination chemistry.

Emergence of Ni-Based Chalcogenides (S and Se) for Clean Energy Conversion and Storage

Nickel chalcogenide (S and Se) based nanostructures intrigued scientists for some time as materials for energy conversion and storage systems. Interest in these materials is due to their good electrochemical stability, eco-friendly nature, and low cost. The present review compiles recent progress in the area of nickel-(S and Se)-based materials by providing a comprehensive summary of their structural and chemical features and performance. Improving properties of the materials, such as electrical conductivity and surface characteristics (surface area and morphology), through strategies like nano-structuring and hybridization, are systematically discussed. The interaction of the materials with electrolytes, other electro-active materials, and inactive components are analyzed to understand their effects on the performance of energy conversion and storage devices. Finally, outstanding challenges and possible solutions are briefly presented with some perspectives toward the future development of these materials for energy-oriented devices with high performance.

The application of transition metal sulfide Ni3S4/CNFs in rechargeable Ni–Zn batteries

We attempt to apply Ni3S4/CNFs into the Ni–Zn battery. After assembling the battery, it shows a notable specific capacity of 215 mA h g−1 at a current density of 5 A g−1.

Co(OH)2@MnO2 nanosheet arrays as hybrid binder-free electrodes for high-performance lithium-ion batteries and supercapacitors

Co(OH)₂@MnO₂ nanosheet arrays were directly grown on nickel foam via two-step electrodeposition method with subsequent heat treatment at 170 °C.

Controllable fabrication of nickel sulfides with enhanced electrochemical performance

In this work, nickel sulfides are fabricated from thiourea and Ni precursor through a hydrothermal method.

Flower-like Ni–Co hydroxides on Ni foam for high-performance supercapacitor applications

Self-supporting Ni–Co hydroxides were synthesized, which exhibit a high areal capacity.

Synthesis of cobalt-doped nickel sulfide nanomaterials with rich edge sites as high-performance supercapacitor electrode materials

Edge site enrichment enhanced the electrochemical performance of Ni_0.75Co_0.25S₂ for supercapacitor application.