12035-50-6

Basic information

• Product Name: NICKELSULFIDE
• Synonyms: SULPHIDICNICKEL
• CAS NO: 12035-50-6
• Molecular Formula: NiS2
• Molecular Weight: 122.83
• Mol File: 12035-50-6.mol
• Article Data: 63

Chemical Properties

• Appearance: /
• CAS DataBase Reference: NICKELSULFIDE(CAS DataBase Reference)
• NIST Chemistry Reference: NICKELSULFIDE(12035-50-6)
• EPA Substance Registry System: NICKELSULFIDE(12035-50-6)

Safety Data

• Hazard Codes: T,Xi:
• Statements: R45-20/21/22-36/37/38:
• Safety Statements: S53-26-36/37/39-45:
• Hazardous Substances Data: 12035-50-6(Hazardous Substances Data)

Usage

General Description

Nickel sulfide, also known as nickel(II) sulfide, is a chemical compound composed of nickel and sulfur with the molecular formula NiS. It is a black or dark green solid that is insoluble in water. Nickel sulfide is commonly used in the production of nickel metal, as a catalyst for organic synthesis, and in the manufacturing of rechargeable batteries. It is also used in the production of pigments and as a precursor to other nickel compounds. Nickel sulfide is considered to be a hazardous substance and can pose health risks if not handled properly. It is important to follow safety precautions when working with this chemical.

InChI:InChI=1/Ni.2S/rNiS2/c2-1-3

Upstream product

• 7704-34-9 sulfur 
• 7783-06-4 hydrogen sulfide 
• 1313-99-1 nickel(II) oxide 
• 7440-02-0 nickel 
• 83864-14-6 nickel dichloride 
• 75-15-0 carbon disulfide 
• 62-55-5 thioacetamide 
• 22868-13-9 sodium disulfide 
• 17356-08-0 thiourea 
• 373-02-4 nickel diacetate 
• 23550-45-0 disulfane 
• 79-19-6 thiosemicarbazide 

Relevant articles and documents

Supercritical fluid processing for the synthesis of NiS2 nanostructures as efficient electrocatalysts for electrochemical oxygen evolution reactions

In this work, the synthesis of NiS2 nanostructures using a simple and one-step environmentally benign supercritical fluid processing technique within 60 min of reaction time has been demonstrated. Structural and morphological characterization has been performed to confirm that the as-synthesized products are cubic NiS2 nanostructures. Interestingly, the as-prepared NiS2 nanostructures exhibit superior electrocatalytic activity towards the oxygen evolution reaction with a small overpotential of 264 mV vs. RHE at 10 mA cm-2 and a Tafel slope of 105 mV dec-1. Remarkably, the observed catalytic activity of the NiS2 nanostructures bears close resemblance to that of the benchmark IrO2 catalyst, where IrO2 shows an overpotential of 260 mV with a Tafel slope of 95 mV dec-1. Thus, the as-synthesized NiS2 nanostructures can be considered as a promising material for the replacement of noble metal-based IrO2 catalysts.

Synthesis ofn-hydrated nickel sulfates from mechanically alloyed nanocrystalline nickel sulfides

In this work, hydrated nickel sulfates (NSHs) were spontaneously obtained by storing nanocrystalline nickel sulfide composites (NiS2-NiS) under ambient conditions over several months. The samples containing different proportions of NiS2-NiS nanophases were produced by mechanochemistry by simply ball-milling Ni and S elements in Ni34S66composition in the absence of solvent. X-ray powder diffraction (XRPD) was used to follow the evolution of phase transitions of the milled samples over about 5 years. A few weeks after the milling process, the monoclinic NiSO4·6(H2O) phase is detected. Rietveld analysis showed that the NiS2and NiS phase fractions decrease over time, and more than 90% of nickel sulfate hexahydrate is present in the end product of the sample with a milling time of 24 h. The small crystallite size phases (～20 nm) and high micro-strain of the nickel sulfide nanophases favor this process, suggesting that sulfate nucleation occurs at disordered regions, also called the interfacial component, and that the growth rates are determined by the exposure time of the sample to the ambient atmosphere. DSC analysis shows at least one phase transition, dehydration and the presence of sulfur in some aged samples. Magnetic measurements at room temperature indicate mixed magnetism in the fresh samples and paramagnetic behavior in the aged ones. We have also observed that the growth of the NSH phases can be accelerated by keeping the samples under high humidity conditions, reaching more than 80% of NSH phases after 35 days. The chemical reactions involved in the milling and aging, as well as a tentative model to explain this spontaneous composition transition from nickel sulfides to nickel sulfate hydrates, are presented.

Hydrothermal synthesis of NiS nanobelts and NiS2 microspheres constructed of cuboids architectures

NiS nanobelts of hexagonal phase have been hydrothermally synthesized starting from Ni(CH3COO)2·4H2O and Na2S2O3·5H2O at 200 °C for 12 h. The as-prepared nanobelts were 50 nm thi

Mesoporous NiS2 nanospheres as a hydrophobic anticancer drug delivery vehicle for synergistic photothermal-chemotherapy

To overcome the unfavorable effects of the hydrophobicity of drugs and cancer resistance, mesoporous NiS2 nanospheres (mNiS2 NSs) have been successfully developed here to package hydrophobic camptothecin (CPT) and realize the synergistic photothermal-chemotherapy of cancer. The mNiS2 NSs which were prepared through a facile solvothermal method here exhibited not only considerable near-infrared (NIR) absorption and good photothermal conversion efficiency as high as 44.6%, but also achieved a NIR light induced CPT release property which were both beneficial for improving the cancer cell-killing efficacy. After a short period of NIR light illumination, a significant intensified cell killing efficacy was observed when 4T1 or HepG2 cancer cells were incubated with CPT@mNiS2 NSs. Thus, mNiS2 NSs have been demonstrated here to have potential as a novel NIR light-responsive hydrophobic drug delivery nanoplatform for realizing synergistic cancer treatment.

Electron-diffraction study on behaviors of metals deposited on crystal surfaces. Part I. Metals deposited on galena

-

Mesoporous NiS2 Nanospheres Anode with Pseudocapacitance for High-Rate and Long-Life Sodium-Ion Battery

It is of great importance to exploit electrode materials for sodium-ion batteries (SIBs) with low cost, long life, and high-rate capability. However, achieving quick charge and high power density is still a major challenge for most SIBs electrodes because of the sluggish sodiation kinetics. Herein, uniform and mesoporous NiS2 nanospheres are synthesized via a facile one-step polyvinylpyrrolidone assisted method. By controlling the voltage window, the mesoporous NiS2 nanospheres present excellent electrochemical performance in SIBs. It delivers a high reversible specific capacity of 692 mA h g?1. The NiS2 anode also exhibits excellent high-rate capability (253 mA h g?1 at 5 A g?1) and long-term cycling performance (319 mA h g?1 capacity remained even after 1000 cycles at 0.5 A g?1). A dominant pseudocapacitance contribution is identified and verified by kinetics analysis. In addition, the amorphization and conversion reactions during the electrochemical process of the mesoporous NiS2 nanospheres is also investigated by in situ X-ray diffraction. The impressive electrochemical performance reveals that the NiS2 offers great potential toward the development of next generation large scale energy storage.

Formic Acid, a Ubiquitous but Overlooked Component of the Early Earth Atmosphere

Terrestrial volcanism has been one of the dominant geological forces shaping our planet since its earliest existence. Its associated phenomena, like atmospheric lightning and hydrothermal activity, provide a rich energy reservoir for chemical syntheses. Based on our laboratory simulations, we propose that on the early Earth volcanic activity inevitably led to a remarkable production of formic acid through various independent reaction channels. Large-scale availability of atmospheric formic acid supports the idea of the high-temperature accumulation of formamide in this primordial environment.

Atomic-Level Coupled Interfaces and Lattice Distortion on CuS/NiS2 Nanocrystals Boost Oxygen Catalysis for Flexible Zn-Air Batteries

The exploration of highly efficient nonprecious metal bifunctional electrocatalysts to boost oxygen evolution reaction and oxygen reduction reaction is critical for development of high energy density metal-air batteries. Herein, a class of CuS/NiS2 interface nanocrystals (INs) catalysts with atomic-level coupled nanointerface, subtle lattice distortion, and plentiful vacancy defects is reported. The results from temperature-dependent in situ synchrotron-based X-ray absorption fine spectroscopy and electron spin resonance spectroscopy demonstrate that the lattice distortion of 14.7% in CuS/NiS2 caused by the strong Jahn–Teller effect of Cu, the strong atomic-level coupled interface of CuS and NiS2 domains, and distinct vacancy defects can provide numerous effective active sites for their excellent bifunctional performance. A liquid Zn-air battery with the CuS/NiS2 INs as air electrode displays a large peak power density (172.4 mW cm?2), a high specific capacity (775 mAh gZn ?1), and long cycle life (up to 83 h), making the CuS/NiS2 INs among the best bifunctional catalysts for Zn-air battery. More remarkably, the flexible CuS/NiS2 INs-based solid-state Zn-air batteries can power the LED after twisting, making them be promising in portable and wearable electronic devices.

Prussian blue-derived synthesis of uniform nanoflakes-assembled NiS2 hierarchical microspheres as highly efficient electrocatalysts in dye-sensitized solar cells

It's urgent and challenging to explore cost-effective and robust electrocatalyst in the development of large-scaled dye-sensitized solar cells (DSSCs). In this work, we develop a novel strategy to prepare 3D hierarchical NiS2 microspheres constructed by nanoflakes through a facile chemical etching/anion exchange reaction. Nickel-cobalt Prussian blue analogous (PBA) nanocubes and (NH4)2S are employed to initially produce uniform γ-NiOOH/NiSx hierarchical microspheres, which were then converted to uniform 3D hierarchical NiS2 microspheres by a controlled annealing treatment. Due to their favorable structural features, the as-obtained NiS2 hierarchical microspheres possess large surface areas, high structural void porosity and accessible inner surface. All of these advantages facilitate the mass diffusion and charge transport between electrolyte and counter electrode material. As a result, the titled NiS2 hierarchical microspheres exhibit excellent electrocatalytic activity toward the reduction of I3- ions in DSSCs. A typical DSSC with NiS2 achieves an impressive power conversion efficiency of 8.46% under AM1.5G illumination (100 mW cm-2), higher than that of pyrolysis Pt electrodes (8.04%). Moreover, the fast activity onset and relatively long stability further demonstrate that the NiS2 hierarchical microspheres are promising alternatives to Pt in DSSCs.

Controlled synthesis and morphology evolution of nickel sulfide micro/nanostructure

A facile hydrothermal method has been developed for synthesis of nickel sulfide micro/nanostructure using Ni(NO3)2·6H 2O as nickel source, SC(NH2)2 as sulfur source and 1,2-ethylenediamin/sodium dodecyl sulfate as surfactant. Different morphologies such as petal-, urchin- and sphere-like nickel sulfide structures have been synthesized by tuning the reaction time, reaction temperature, and the surfactant. The as-prepared products were characterized by X-ray diffraction, Field-emission scanning electron microscope, and Photoluminescence spectra. The relationship of the fluorescence properties with their morphology and phase was studied, and the possible growth mechanism of nickel sulfide structure was proposed based on the morphology evolution of nickel sulfide.

Localized NiS2 Quantum Dots on g-C3N4 Nanosheets for Efficient Photocatalytic Hydrogen Production from Water

Developing high-efficiency yet low-cost photocatalyst for solar hydrogen production by avoiding the use of noble metals has received adequate interest but remains a great challenge to date. This work reports a seed-mediated hydrothermal approach for the synthesis of NiS2 quantum dots (QDs) anchored two-dimensional graphitic carbon nitride (g-C3N4) nanosheets. This hybrid shows superior performance toward photocatalytic H2 evolution from water. The highest H2 evolution rate reaches 4.841 μmol h?1, with an apparent quantum efficiency of 2 % at 425 nm, which is even much higher than that of Pt-modified g-C3N4 photocatalyst (2.865 μmol h?1). Moreover, the composite presents good stability without notable activity decay after several cycled tests. It is found that NiS2 QDs are essential for this improvement. These small nanoclusters not only benefit rapid and vectorial diffusion of photogenerated electrons from g-C3N4 to NiS2, but also promote H2 evolution by decreasing the thermodynamic overpotential for proton reduction. This work thus marks an important step toward designing good-performance and low-cost photocatalytic materials for solar H2 conversion.

Neutral-pH overall water splitting catalyzed efficiently by a hollow and porous structured ternary nickel sulfoselenide electrocatalyst

Development of nonprecious, efficient, and stable electrocatalysts for overall water splitting under mild conditions is crucial but still a huge challenge for the renewable energy techniques. Herein, a facile hydrothermal and then selenization strategy is proposed to synthesize hierarchical nickel sulfoselenide (NiS2(1-x)Se2x) hollow/porous spheres with controllable composition for electrocatalytic water splitting in neutral media. By regulating the degree of selenization, the Se/S atomic ratio in the nickel sulfoselenides can be controlled to realize the tunable electronic structure of nickel to boost its intrinsic activity. Benefiting from their unique structural features and the anion doping effect, nickel sulfoselenides, especially with the chemical composition Ni(S0.5Se0.5)2, are discovered to exhibit high activity and stability toward both hydrogen and oxygen evolution reactions under neutral conditions. When using Ni(S0.5Se0.5)2 as a bifunctional electrode as both the anode and cathode in a neutral electrolyte, it demonstrates a durable activity for overall water splitting to drive 10 mA cm-2 at a cell voltage of merely 1.87 V, outperforming the noble metal-based Pt/C and IrO2 couple. This study not only offers a new type of promising earth-abundant electrocatalyst towards water electrolysis under benign conditions, but also highlights that anion doping engineering or composition control can be an elegant strategy to improve the electrochemical catalytic performance.

Solvothermal growth of NiS single-crystalline nanorods

Nanorods of NiS were successfully prepared by a solvothermal synthetic route using S and Ni powders as reagents in ethylenediamine (en) solvent at the temperature of 200 °C. The as prepared NiS nanorods were characterized by X-ray diffraction (XRD), field

Unveiling the Promotion of Surface-Adsorbed Chalcogenate on the Electrocatalytic Oxygen Evolution Reaction

Transition metal chalcogenides (TMCs) are efficient oxygen evolution reaction (OER) pre-electrocatalysts, and will in situ transform into metal (oxy)hydroxides under OER condition. However, the role of chalcogen is not fully elucidated after oxidation and

Novel thiourea derivative and its complexes: Synthesis, characterization, DFT computations, thermal and electrochemical behavior, antioxidant and antitumor activities

A novel thiourea derivative, N-((2-chloropyridin-3-yl)carbamothioyl) thiophene-2-carboxamide,C11H8ClN3OS2 (HL) and its Co(II), Ni(II) and Cu(II) complexes (ML2 type) were prepared and characterized by elemental analysis, FT-IR,1H NMR and HR-MS methods. The crystal structure of HL was also investigated by single crystal X-ray diffraction study. The HL crystallizes in the orthorhombic crystal system with P 21 21 21 space group, Z?=?4, a?=?3.8875(3)??, b?=?14.6442(13)??, c?=?21.8950(19)??. The [ML2] complex structures were optimized by using B97D/TZVP level. Molecular orbitals of HL ligand were calculated at the same level. Thermal and electrochemical behaviors of the complexes were investigated. Anticancer and antioxidant activities of the complexes were also investigated. Antioxidant activities were determined by using DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) assays. Anticancer activities were studied via MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in MCF-7 (Michigan Cancer Foundation-7) breast cancer cells.

On the synthesis of sulphides in combustion regime

The present investigation deals with combustion (in inert atmosphere) of mixtures based on metal nitrates and sulphur-containing compounds possessing reductive properties, such as ammonium thiocyanate, thiosemicarbazide, thiocarbamide. It is demonstrated

Engineering yolk-shell P-doped NiS2/C spheresviaa MOF-template for high-performance sodium-ion batteries

Transition metal sulfides generally demonstrate unsatisfactory capacity and a limited rate capability that still restrict their application for sodium-ion batteries. Herein, yolk-shell P-doped NiS2/C spheres were synthesizedviaa Ni-MOF template with phytic acid acting as a P source to significantly enhance the sulfide's sodium storage property. The yolk-shell P-doped NiS2/C spheres exhibited an ultrahigh initial discharge and charge capacities of 3546.7 and 2622.9 mA h g-1with 72.9% coulombic efficiency, and maintained a relatively high reversible capacity of 1113.5 mA h g-1at 0.1 A g-1after 20 cycles. Electrochemical measurements further revealed that the yolk-shell P-doped NiS2/C spheres could also deliver a good rate capability and stable long-term cycling performance with 766.8 mA h g-1reversible capacity at 0.5 A g-1after 400 cycles. The satisfactory electrochemical results could be ascribed to the confinement and synergistic effect from the robust yolk-shell framework and heteroatom P doping. Therefore, it was demonstrated that morphology tuning and heteroatom P doping can serve as effective strategies to significantly improve the electrochemical properties of transition metal sulfides for sodium-ion batteries.

An effective photocatalytic hydrogen evolution strategy based on tunable band gap (CuIn)xZn2(1?x)S2combined with amorphous molybdenum sulfide

Fully utilizing the visible light and lowering the economic costs are the toughest challenges of photocatalytic water splitting. To address these issues, a non-noble metal photocatalyst, (CuIn)xZn2(1?x)S2solid solution with an adjustable band gap by modifying its composition, was synthesized. In addition, amorphous molybdenum sulfide (a-MoSx) was compounded as a co-catalyst on the surface of the solid solution. Compared with crystalline molybdenum sulfide (MoS2), a-MoSxcan provide more active sites and reduce the activation energy of hydrogen evolution reactions more effectively. The (CuIn)0.2Zn1.6S2(CIZS) photocatalyst loaded with 3 wt% a-MoSxexhibited the best photocatalytic performance with a hydrogen evolution rate of 2100 μmol g?1h?1

Effect of phosphorus content in nickel phosphide catalysts studied by XAFS and other techniques

A series of novel, high-activity supported nickel phosphide hydroprocessing catalysts (Ni2P/SiO2) was synthesized using TPR. The effect of P content on hydroprocessing performance and catalyst structure was studied. The activity of the catalysts was evaluated in a three-phase trickle-bed reactor operated at 3.1 MPa and 643 K in HDN and HDS of a model liquid feed containing 2000 ppm nitrogen (quinoline), 3000 ppm sulfur (dibenzothiophene), 500 ppm oxygen (benzofuran), 20 wt % aromatics (tetralin), and balance aliphatics (tetradecane). The product of dibenzothiophene HDS was biphenyl. The products of quinoline reaction were propylbenzene and propylcyclohexane, 1,2,3,4- and 7,8,9,10-tetrahydroquinoline, and propylaniline. The product of benzofuran reaction was exclusively ethylbenzene. The product of tetralin reaction was naphthalene, with some cis- and trans-decalin. At lower P content, some Ni metal and Ni12P5 were obtained, and at higher P content, the Ni2P active phase was blocked by excess phosphorus. On these catalysts, HDN reactions were structure sensitive, while the HDS reactions were structure insensitive.

Size-dependent and intra-band photoluminescence of NiS2 nano-alloys synthesized by microwave assisted hydrothermal technique

Synthesis of nickel disulfide (NiS2) nano-alloys capped and uncapped with hexadecylamine (HDA) was carried out. A cubic phase NiS 2 formation was confirmed by X-ray diffraction (XRD) analysis. An average crystallite size of 35 nm was obtained for the uncapped nanostructures and 9 nm was obtained for the capped nanostructures estimated using the Scherrer equation. Unexpected ultra-violet (UV) emission as well as near infrared (IR) emissions were attributed to intra-band energy state transitions that occur as a result of the porous structure of the material. Enhanced UV and near IR PL emissions due to the smaller crystallite size of the capped NiS2 nanostructures was also observed. Band energy and local density of states calculation for NiS2 were used to support the experimentally observed luminescence results. The luminescence features at wavelengths of 400 nm (3.10 eV), 428 nm (2.90 eV), 447 nm (2.77 eV) and 464 nm (2.67 eV) can be attributed to some of those electrons de-exciting from S (3p) levels down to the Ni (3d) (blue to UV emission) whereas those features at wavelengths of 710 nm (1.75 eV), 751 nm (1.65 eV), 754 nm (1.64 eV), [NiS2/HDA-capped NiS2] and 784 nm (1.58 eV) respectively seem to result from de-excitations between either Ni(3d) or S (3s, 3p) levels and Ni-S hybridization levels (red to near IR emission).

Unoccupied electronic states in NiS2-xSex across the metal-insulator transition

We investigate the evolution of the electronic structure across the insulator-metal transition in NiS2-xSex with changing composition, but in the absence of any structural or magnetic changes. A comparison of the inverse photoemission spectra with band-structure calculations establishes the importance of correlation effects in these systems. Systematic changes in the spectral distribution establish the persistence of the upper Hubbard band well into the metallic regime, with the insulator-to-metal transition being driven by a transfer of spectral weight from the Hubbard band to states close to the Fermi energy.

Synthesis of nickel sulfides by mechanical alloying

The feasibility and kinetics of synthesizing various nickel sulfides by milling of elemental mixtures of Ni and S in a high-energy shaker mill have been investigated. The phases Ni3S2 and the high-temperature polymorph of NiS are formed readily via such processing. In distinction, it requires prolonged milling to obtain Ni7S6; NiS2 can only be obtained as a minor reaction product; and Ni3S4 cannot be formed by milling for the conditions of this study. Structural evolution during synthesis and the kinetics of Ni3S2 formation are investigated in depth. S coats the Ni particles and sulfide formation takes place at the interface of the elements after a certain degree of microstructural refinement due to the plastic deformation accompanying milling. Ni3S2 forms rapidly at this stage. However, a stasis in the reaction is then observed. This is associated with NIS formation and a slight decrease in the amount of Ni3S2. The stasis is of approximately 5-min duration and is followed by a recurrence in the formation of Ni3S2 and a disappearance of the NiS phase. The kinetics can be mimicked through a model of the mechanical alloying process. The model is able to predict the time dependence of the initial and later stages of Ni3S2 formation and the effect of other parameters, such as mill atmosphere and use of premilled powder, on the reaction kinetics. The microstructures found in the intermediate to later stages of milling are similar to those associated with self-sustaining reactions.

New Solid-Gas Metathetical Synthesis of Binary Metal Polysulfides and Sulfides at Intermediate Temperatures: Utilization of Boron Sulfides

A new simple synthetic method for binary metal polysulfides and sulfides was developed by utilizing an in situ formation of boron sulfides and their subsequent reactions with metal-source oxides in a closed container at intermediate temperatures above 350 °C at which the boron sulfides react in a gaseous form. The versatility of the new method is demonstrated with oxides of various transition metals (Ti, V, Mn, Fe, Ni, Nb, Mo, Ru, and W) and rare-earth metals (Y, Ce, Nd, Sm, Eu, Tb, and Er) as starting materials that exhibit different chemical characteristics. Regardless of the oxidation states of metals in the starting materials, the sulfidation reactions occurred quantitatively with stoichiometric mixtures of boron and sulfur, and within 24 h the reactions yielded pure products of TiS2, TiS3, VS4, FeS2, NiS2, NbS3, MoS 2, RuS2, WS2, Y2S3, and RS2 (R = Ce, Nd, Sm, Eu, Tb, and Er) which were the thermodynamically stable phases under the reaction conditions. The scope and implications of the new sulfidation method are also discussed.

Nickel sulfides for electrocatalytic hydrogen evolution under alkaline conditions: A case study of crystalline NiS, NiS2, and Ni3S2 nanoparticles

Electrocatalytic water splitting to produce H2 plays an important role in the capture, conversion, and storage of renewable energy sources, such as solar energy and wind power. As the reductive half reaction of water splitting, H2 evolution reaction (HER) suffers from sluggish kinetics, and hence competent HER catalysts are needed. Despite being excellent HER catalysts, noble metal-based catalysts (i.e. Pt) are too expensive to be economically competitive. Therefore, low-cost catalysts composed of solely earth-abundant elements have attracted increasing attention these years, among which nickel-based HER catalysts, particularly nickel chalcogenides, are considered as promising candidates. Although many nickel chalcogenides, including NiS, NiS2, and Ni3S2, have been reported for hydrogen evolution, their intrinsic catalytic activities have never been investigated and compared in detail under the same conditions. Most of the previous investigations were limited to only one species of nickel chalcogenides under very unique conditions, rendering a fair comparison of their HER activities impossible. Herein, we report the preparation and characterization of three crystalline nickel sulfides, NiS, NiS2, and Ni3S2, with comparable crystal sizes and specific surface areas. Detailed electrochemical studies under strongly alkaline conditions coupled with theoretical computations were performed to probe their intrinsic HER activities, resulting in the order of Ni3S2 > NiS2 > NiS. The superior HER performance of Ni3S2 mainly stems from the combined effect of large electrochemically active surface area and high conductivity (metallic conductor vs. semiconductor).

Shell-strengthened hollow architecture of NiCo2S4 carved through an in-situ reaction Ostwald Ripening mechanism with significantly enhanced electrochemical performance

For Faraday supercapacitors, some battery-type electrode materials such as nickel-based materials attract intensive attention by virtue of their high theoretical capacity. However, it is quite difficult for these materials to achieve the satisfied high-rate performance and cycling life concurrently due to the contradiction of their individual requirements to the microscopic structure of materials. In this work, we build a hollow architecture of NiCo2S4 at hydrothermal condition following an in-situ reaction Ostwald Ripening mechanism. The as-prepared NiCo2S4 presents a shell-strengthened hollow structure, satisfying the as-mentioned two requirements: (1) the rich pores in shell and hollow structure plus structural cobalt ions lead to the excellent high-rate performance of NiCo2S4; (2) the dense particulate layer in shell with additional mechanical strength prolongs the cycling life of NiCo2S4. Consequently, the asymmetrical supercapacitors assembled with NiCo2S4 as positive electrode material show both high energy and power densities, and excellent cycling stability.