Ni3S2 Nanosheets Research Articles

In situ preparation of NiS2/CoS2 composite electrocatalytic materials on conductive glass substrates with electronic modulation for high-performance counter electrodes of dye-sensitized solar cells

The electrocatalytic composite materials of honeycomb structure NiS2 nanosheets loaded with metallic CoS2 nanoparticles are in situ prepared on F doped SnO2 conductive glass (FTO) substrates used as counter electrodes of DSSCs through chemical bath deposition (CBD) and sulfidizing process. Single crystalline NiS2 honeycomb structure array lay a foundation for the large surface area of NiS2/CoS2 composite CEs. The formed NiS2/CoS2 nanointerface modulates electronic structure of composite CEs from the synergetic interactions between CoS2 nanoparticles and NiS2 nanosheets, which dramatically improves the electrocatalytic activity of NiS2/CoS2 composite CEs; Metallic CoS2 nanoparticles covering NiS2 nanosheets electrodes adjusts the electrodes' structure and then reduces the series resistance (Rs) and the Nernst diffusion resistance (Zw) of counter electrodes. The improvement of these areas greatly enhances the electrocatalytic performance of CEs and the short circuit current density (Jsc) and Fill factor (FF) of DSSCs. Impressively, the DSSC based on NiS2/CoS2-0.1 CE shows the best photovoltaic performance with photovoltaic conversion efficiency of 8.22%, which is 24.36% higher than that (6.61%) of the DSSC with Pt CE. And the NiS2/CoS2-0.1 CE also displays a good stability in the iodine based electrolyte. This work indicates that rational construction of composite electrocatalytic materials paves an avenue for high-performance counter electrodes of DSSCs.

3D structured Mo-doped Ni3S2 nanosheets as efficient dual-electrocatalyst for overall water splitting

Searching for a cost-effective, high efficient and stable bifunctional electrocatalyst for overall water-splitting is critical to renewable energy systems. In this study, three-dimensional (3D) curved nanosheets of Mo-doped Ni3S2 grown on nickel foam were successfully synthesized via a one-step hydrothermal process. The hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) in alkaline environment of this 3D catalyst are investigated in detail. The results show that it possesses lower overpotential, high current densities and small Tafel slopes both in OER and HER. For HER, the catalysts show excellent electrochemical performance, demonstrating a low over-potential of 212 mV at 10 mA cm−2 with a large decrease of 127 mV compared to the undoped Ni3S2. And it also shows a lower overpotential of 260 mV at 10 mA cm−2 which decreases 30 mV for OER. In addition, it is only need 1.67 V for the overall water splitting at 10 mA cm−2 which is 70 mV. It found that the Mo element would change the morphology of Ni3S2 and induce much more active sites for HER and OER. The as-prepared Mo-doped Ni3S2 bi-functional electrocatalyst could act as the promising electrode materials for water splitting.

Tailoring synthesis of Ni3S2 nanosheets with high electrochemical performance by electrodeposition

Nickel sulfide nanosheets with high electrochemical performance were successfully synthesized by an electrochemical deposition method. It is interesting to notice that the size, thickness and surface area were simply tailored by adjusting the initial potential during synthesis without changing other reaction conditions. The highest electrochemical performance was achieved on the nickel sulfide sample prepared at initial potential of −0.9 V. This sample not only presented high specific capacitance at low current density (1958.0F g−1 at 3.3 A g−1), but also exhibited excellent high rate performance (672.8F g−1 at 98.7 A g−1). To the best of our knowledge, these values are in the highest level as compared with other works. The high electrochemical performance of nickel sulfide sample originates from its thin thickness.

Ni3S2 Nanosheets in Situ Epitaxially Grown on Nanorods as High Active and Stable Homojunction Electrocatalyst for Hydrogen Evolution Reaction

Development of efficient noble metal-free electrocatalysts for accelerating the sluggish kinetics in the hydrogen evolution reaction (HER) has received a great deal of attention in electrolytic water splitting. Herein, we present a facile one-step solvothermal strategy for controllably constructing the homojunction structures of Ni3S2 nanosheets in situ epitaxially grown on nanorods by using Ni foam as self-support substrate and nickel resource (Ni3S2/NF). In the synthesis, cetyltrimethylammonium bromide and hydrazine hydrate are used to control the formation of nanorods and nanosheets, respectively. The special 3D Ni3S2 nanorods@nanosheets homojunction could provide plentiful catalytically active sites; meanwhile, the intimate contact between Ni3S2 and Ni foam could enhance the long-term stability. The inevitable sulfur vacancies in the Ni3S2 could tune electronic structure of the surface and enhance the catalytic activity. The synergistic effect leads to the as-prepared Ni3S2/NF exhibiting a superior HE...

Vapor-phase hydrothermal transformation of a nanosheet array structure Ni(OH)2 into ultrathin Ni3S2 nanosheets on nickel foam for high-efficiency overall water splitting

Ultrathin Ni3S2 nanosheets grown on nickel foam are thermodynamically favourable for hydrazine adsorption and oxidation, exhibiting superior H2 generation performance.

Temperature dependence of Ni3S2 nanostructures with high electrochemical performance

Different Ni3S2 nanostructures have been successfully synthesized at different temperatures by a facile and efficient solvothermal method. The Ni3S2 nanostructures with three-dimensional (3D) nanosheets array and silkworm eggs-like morphologies were obtained by adjusting the reaction temperature. A large number of 3D nanosheets are interconnected to form an open network structure with porous of Ni3S2 at 180 °C, and electrochemical tests showed that the special structure exhibited the outstanding specific capacitance (1357 F g −1 at 1 A g−1) and excellent cycling stability (maintained 91% after 3000 cycles). In comparison, the performance of Ni3S2 silkworm eggs-like structure is not very perfect. This may be due to the fact that the 3D nanosheets with porous structure can improve the electrochemical performance by shortening effectively the diffusion path of electrolyte ions and increasing the active sites during charging and discharging. Among them, the reaction temperature is the main factor to control the formation of the 3D nanosheets array. These results indicated the Ni3S2 nanosheets promising applications as high-performance supercapacitor electrode materials.

Electronic Structure Reconfiguration toward Pyrite NiS2 via Engineered Heteroatom Defect Boosting Overall Water Splitting.

Developing highly active and low-cost heterogeneous catalysts toward overall electrochemical water splitting is extremely desirable but still a challenge. Herein, we report pyrite NiS2 nanosheets doped with vanadium heteroatoms as bifunctional electrode materials for both hydrogen- and oxygen-evolution reaction (HER and OER). Notably, the electronic structure reconfiguration of pyrite NiS2 is observed from typical semiconductive characteristics to metallic characteristics by engineering vanadium (V) displacement defect, which is confirmed by both experimental temperature-dependent resistivity and theoretical density functional theory calculations. Furthermore, elaborate X-ray absorption spectroscopy measurements reveal that electronic structure reconfiguration of NiS2 is rooted in electron transfer from doped V to Ni sites, consequently enabling Ni sites to gain more electrons. The metallic V-doped NiS2 nanosheets exhibit extraordinary electrocatalytic performance with overpotentials of about 290 mV for OER and about 110 mV for HER at 10 mA cm-2 with long-term stability in 1 M KOH solutions, representing one of the best non-noble-metal bifunctional electrocatalysts to date. This work provides insights into electronic structure engineering from well-designed atomic defect metal sulfide.

Cobalt Doping To Boost the Electrochemical Properties of Ni@Ni3 S2 Nanowire Films for High-Performance Supercapacitors.

Metal sulfides have aroused great interest for energy storage. However, their low specific capacities and inferior rate capabilities hinder their practical applications. In this work, a facile cobalt-doping process is used to boost the electrochemical performance of Ni@Ni3 S2 core-sheath nanowire film electrodes for high-performance electrochemical energy storage. Co ions are doped successfully and uniformly into Ni3 S2 nanosheets through a facile ion-exchange process. The electrochemical properties of film electrodes are improved greatly, and an ultrahigh volumetric capacity (increased from 105 to 730 C cm-3 at 0.25 A cm-3 ) and excellent rate capability are obtained after Co is doped into Ni@Ni3 S2 core-sheath nanowires. A hybrid asymmetric supercapacitor with Co-doped Ni@Ni3 S2 as the positive electrode and graphene-carbon nanotubes as the negative electrode is assembled and exhibits an ultrahigh volumetric capacitance of 142 F cm-3 (based on the total volume of both electrodes) at 0.5 A cm-3 and excellent cycling stability (only 3 % capacitance decrease after 5000 cycles). Moreover, the volumetric energy density can reach 44.5 mWh cm-3 , which is much larger than those of thin-film lithium batteries (1-10 mWh cm-3 ). These results may provide useful insights for the fabrication of high-performance film electrodes for energy-storage applications.

Ni3S2 Nanosheet Flowers Decorated with CdS Quantum Dots as a Highly Active Electrocatalysis Electrode for Synergistic Water Splitting.

A facile and effective strategy for fabricating a three-dimensionally (3D) structured nanocomposite catalyst based on nonprecious metals for water splitting in alkaline electrolyzers is reported in this paper. This nanocomposite catalyst consists of the CdS quantum dots (QDs) decorated Ni3S2 nanosheet flowers deposited on the plasma-treated nickel foam (PNF). The NiO formed during the plasma treatment is shown to play an important role for pushing the hydrogen and oxygen evolution reactions (HER and OER) in alkaline media. The enhanced exposure of active sites on the nanopetalages results in superior catalytic performance for promoting HER and OER in alkaline electrolyzers. Specifically, a current density of 10 mA cm-2 can be achieved for the HER with a 121 mV overpotential when the working electrode based on the 1 mM CdS/Ni3S2/PNF catalyst is employed in 1 M KOH. The corresponding Tafel slope is 110 mV/decade. For the OER, the onset potential can be as low as 1.25 V vs reversible hydrogen electrode (RHE) reference electrode, which is substantially lower than the commercial IrO2 catalyst (∼1.47 V). This nanostructured catalyst has excellent long-term stability, and the linear scan voltammetry (LSV) curves of the HER and OER in 1 M KOH solution show negligible decay after undergoing 104 cycles of cyclic voltammogram. The nanocomposite material developed in this study is an ideal candidate as a catalyst for splitting water in alkaline media with relatively low overpotentials at reasonably high current densities (≥100 mA cm-2).

Two-dimensional metal chalcogenides analogous NiSe2 nanosheets and its efficient electrocatalytic performance towards glucose sensing

Recently, 2D layered transition-metal dichalcogenide materials have received great consideration because of their unique electronic properties, large surface area and high electrocatalytic activity. In this connection, for the first time the similar nanostructured material of NiSe2 nanosheets (NiSe2-NS) has been synthesized by a facile hydrothermal method for electrocatalytic applications. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-ray analysis (EDX), X-ray diffraction spectrum (XRD) results confirmed the formation of NiSe2-NS with required stoichiometry and morphology. Electrochemical Impedance Spectroscopy (EIS) data indicate that electron transfer is facile at the NiSe2-NS modified glassy carbon electrode (GCE). It has been as an electrode modifier for glucose sensing applications. The electrochemical studies were performed for NiSe2-NS modified GCE using Cyclic Voltammetry (CV) and amperometric i-t techniques. The results are suggesting the effective response of NiSe2-NS/GCE with a very low limit of detection (LOD) and sensitivity of 23nM and 5.6μAμM−1cm−2 respectively. Moreover, the selectivity data exhibited excellent anti-interference property of NiSe2-NS/GCE towards glucose in the presence of possible interfering agents viz. Ascorbic acid, dopamine, glucose.

Facile synthesis of Ni3S2/rGO nanosheets composite on nickel foam as efficient electrocatalyst for hydrogen evolution reaction in alkaline media

Abstract

Incorporating Nitrogen-Doped Graphene Quantum Dots and Ni3 S2 Nanosheets: A Synergistic Electrocatalyst with Highly Enhanced Activity for Overall Water Splitting.

A noble-metal-free electrocatalyst is fabricated via in situ formation of nanocomposite of nitrogen-doped graphene quantum dots (NGQDs) and Ni3 S2 nanosheets on the Ni foam (Ni3 S2 -NGQDs/NF). The resultant Ni3 S2 -NGQDs/NF can serve as an active, binder-free, and self-supported catalytic electrode for direct water splitting, which delivers a current density of 10 mA cm-2 at an overpotential of 216 mV for oxygen evolution reaction and 218 mV for hydrogen evolution reaction in alkaline media. This bifunctional electrocatalyst enables the construction of an alkali electrolyzer with a low cell voltage of 1.58 V versus reversible hydrogen electrode (RHE) at 10 mA cm-2 . The experimental results and theoretical calculations demonstrate that the synergistic effects of the constructed active interfaces are the key factor for excellent performance. The nanocomposite of NGQDs and Ni3 S2 nanosheets can be promising water splitting electrocatalyst for large-scale hydrogen generation or other energy storage and conversion applications.

Nanosheet-assembled NiS hollow structures with double shells and controlled shapes for high-performance supercapacitors

Hollow micro- and nanostructured materials with controllable shapes are appealing materials for electrochemical energy storage devices with high energy and power densities. Herein, double-shelled hollow nickel sulfides with controlled shape (cube-, ellipsoid- and capsule-shaped) were successfully synthesized by using different morphological α-Fe2O3 templates. The as-obtained nickel sulfides have uniform size and well-defined double shells that consist of crossed ultrathin NiS nanosheets. When evaluated as electrode materials for supercapacitors, the capsule-shaped structure exhibits the highest specific capacitance of 1159Fg−1 at a current density of 2Ag−1 due to its high specific surface area (100.2m2g−1), low equivalent series resistance (0.80Ω) and ion diffusive resistance. More importantly, the asymmetric capacitor NiS (capsule-shaped)||RGO@Fe3O4 shows a high energy density of 43.7Whkg−1 at a power density of 664Wkg−1 (21.8Whkg−1 at 8000Wkg−1), and after 5000 charge–discharge cycles, 83.3% of its capacitance is remained at the current density of 5Ag−1.

Three-Dimensional Nickel-Borate Nanosheets Array for Efficient Oxygen Evolution at Near-Neutral pH.

Nickel-borate nanosheets array on titanium mesh (Ni-Bi NA/TM) was derived from NiSe2 nanosheets array on titanium mesh (NiSe2 NA/TM) by electrochemical transformation. As a three-dimensional electrode, Ni-Bi NA/TM exhibited high catalytic activity toward the oxygen evolution reaction and required a low overpotential of 430 mV at 10 mA cm-2 in 0.1 m potassium borate (pH 9.2), with outstanding long-term stability and high turnover frequency.

Constructing Multifunctional Metallic Ni Interface Layers in the g-C3N4 Nanosheets/Amorphous NiS Heterojunctions for Efficient Photocatalytic H2 Generation.

The construction of exceptionally robust and high-quality semiconductor-cocatalyst heterojunctions remains a grand challenge toward highly efficient and durable solar-to-fuel conversion. Herein, novel graphitic carbon nitride (g-C3N4) nanosheets decorated with multifunctional metallic Ni interface layers and amorphous NiS cocatalysts were fabricated via a facile three-step process: the loading of Ni(OH)2 nanosheets, high-temperature H2 reduction, and further deposition of amorphous NiS nanosheets. The results demonstrated that both robust metallic Ni interface layers and amorphous NiS can be utilized as electron cocatalysts to markedly boost the visible-light H2 evolution over g-C3N4 semiconductor. The optimized g-C3N4-based photocatalyst containing 0.5 wt % Ni and 1.0 wt % NiS presented the highest hydrogen evolution of 515 μmol g-1 h-1, which was about 2.8 and 4.6 times as much as those obtained on binary g-C3N4-1.0%NiS and g-C3N4-0.5%Ni, respectively. Apparently, the metallic Ni interface layers play multifunctional roles in enhancing the visible-light H2 evolution, which could first collect the photogenerated electrons from g-C3N4, and then accelerate the surface H2-evolution reaction kinetics over amorphous NiS cocatalysts. More interestingly, the synergetic effects of metallic Ni and amorphous NiS dual-layer electron cocatalysts could also improve the TEOA-oxidation capacity through upshifting the VB levels of g-C3N4. Comparatively speaking, the multifunctional metallic Ni layers are dominantly favorable for separating and transferring photoexcited charge carriers from g-C3N4 to amorphous NiS cocatalysts owing to the formation of Schottky junctions, whereas the amorphous NiS nanosheets are mainly advantageous for decreasing the thermodynamic overpotentials for surface H2-evolution reactions. It is hoped that the implantation of multifunctional metallic interface layers can provide a versatile approach to enhance the photocatalytic H2 generation over different semiconductor-cocatalyst heterojunctions.

Ultrafast Formation of Amorphous Bimetallic Hydroxide Films on 3D Conductive Sulfide Nanoarrays for Large‐Current‐Density Oxygen Evolution Electrocatalysis

Developing nonprecious oxygen evolution electrocatalysts that can work well at large current densities is of primary importance in a viable water-splitting technology. Herein, a facile ultrafast (5 s) synthetic approach is reported that produces a novel, efficient, non-noble metal oxygen-evolution nano-electrocatalyst that is composed of amorphous Ni-Fe bimetallic hydroxide film-coated, nickel foam (NF)-supported, Ni3 S2 nanosheet arrays. The composite nanomaterial (denoted as Ni-Fe-OH@Ni3 S2 /NF) shows highly efficient electrocatalytic activity toward oxygen evolution reaction (OER) at large current densities, even in the order of 1000 mA cm-2 . Ni-Fe-OH@Ni3 S2 /NF also gives an excellent catalytic stability toward OER both in 1 m KOH solution and in 30 wt% KOH solution. Further experimental results indicate that the effective integration of high catalytic reactivity, high structural stability, and high electronic conductivity into a single material system makes Ni-Fe-OH@Ni3 S2 /NF a remarkable catalytic ability for OER at large current densities.

Efficient electrocatalysis of overall water splitting by ultrasmall NixCo3−xS4 coupled Ni3S2 nanosheet arrays

The overall water splitting into hydrogen and oxygen is one of the most promising ways to store intermittent solar and wind energy in the form of chemical fuels. However, this process is quite thermodynamically uphill, and thus needs to be mediated simultaneously by efficient hydrogen evolving and oxygen evolving catalysts to get any feasible output from it. Herein, we report the synthesis of such a catalyst comprising ultrasmall NixCo3−xS4-decorated Ni3S2 nanosheet arrays supported on nickel foam (NF) via a partial cation exchange reaction between NF-supported Ni3S2 nanosheet arrays and cobalt(II) ions. We show that the as-prepared material, denoted as NixCo3−xS4/Ni3S2/NF, can serve as a self-standing, noble metal-free, highly active and stable, bifunctional electrocatalyst for the two half reactions involved in the overall water splitting: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Furthermore, we demonstrate that a high-performance electrolyzer for the overall water splitting reaction can be assembled by using NixCo3−xS4/Ni3S2/NF as the electrocatalyst at both the cathode and the anode sides of the electrolyzer. This electrolyzer delivers water-splitting current densities of 10 and 100mA/cm2 at applied potentials of 1.53 and 1.80V, respectively, with remarkable stability for >200h in both cases. The electrolyzer's performance is much better than the performances of electrolyzers assembled from many types of other bifunctional electrocatalysts as catalyst couple. Moreover, the overall performance of the electrolyzer is comparable with the performances of electrolyzers containing two different, benchmark, monofunctional HER and OER electrocatalyst couple (i.e., Pt/C-IrO2).

Insight into the hydrogen evolution reaction of nickel dichalcogenide nanosheets: activities related to non-metal ligands.

Transition metal dichalcogenides, MX2 (M = Fe, Co, Ni, X = S, Se, Te), have been proven to be promising substitutes for noble metals in hydrogen evolution reactions (HERs). However, forthright comparisons of metal sulfides, metal selenides, and metal tellurides are rarely conducted, let alone the mechanism of the important role of their non-metal ligands. In this paper, we report the pilot study of a controllable method for the preparation of a series of NiX2 (X = S, Se, Te) nanosheets via a facile anion-exchange reaction. Consequently, the HER activities and stabilities of NiS2, NiSe2, and NiTe2 nanosheets were tested in both acid and alkaline solutions. The required overpotentials to reach 10 mA cm-2 in 0.5 M H2SO4 for NiS2, NiSe2, and NiTe2 were 213, 156, and 276 mV, respectively. The best performance of NiSe2 was also confirmed in 1 M KOH. Besides NiS2 and NiTe2 nanosheets, the HER properties of NiSe2 nanosheets are superior to most of the available nickel catalysts. Interestingly, the results from electrochemical measurements were found to be fully consistent with the data based on density function theory calculation. Among various factors that might influence the HER activities of nickel dichalcogenides, the free energies of hydrogen adsorption and conductivities have played important roles.

A Zn-doped Ni3S2 nanosheet array as a high-performance electrochemical water oxidation catalyst in alkaline solution.

It is of high importance to design efficient electrocatalysts for the oxygen evolution reaction (OER) at alkaline pH. In this communication, we report the development of a Zn-doped Ni3S2 nanosheet array on Ni foam (Zn-Ni3S2/NF) as a high-performance and durable electrocatalyst for the OER. Such Zn-Ni3S2/NF drives a catalytic current density of 100 mA cm-2 with the requirement of an OER overpotential of 330 mV, 90 mV less than that for Ni3S2/NF. Furthermore, Zn-Ni3S2/NF demonstrates excellent long-term electrochemical durability maintaining its activity at an overpotential of 300 mV for 20 h.

Hierarchical NiS/N-doped carbon composite hollow spheres with excellent supercapacitor performance

The synthesized NiS nanosheets anchored on N-doped hollow carbon spheres (NHCSs) exhibit excellent electrochemical performance as electrode materials for supercapacitors.