NiCo2S4 Nanoparticles Research Articles

Incorporation of electroactive NiCo2S4 and Fe2O3 into graphene aerogel for high-energy asymmetric supercapacitor

Incorporation of electroactive Fe2O3 and NiCo2S4 (NCS) into graphene aeorgel (GA) is presented in this work. The efficient adsorption of precursor ions on the graphene oxides sheets and subsequent hydrothermal gelation yield the GA-Fe2O3 and GA-NCS composites that can be used as negative and positive electrode, respectively, for constructing a high-energy asymmetric supercapacitor (ASC). Influences of mass contents of Fe2O3 and NCS on capacitive performances of GA-Fe2O3 and GA-NCS electrodes are systematically investigated in KOH aqueous electrolyte. The uniform distribution of Fe2O3 on the graphene sheets (GS) and the NCS nanoparticles wrapped by GS provide sufficient electroactive sites for Faradaic redox reactions, while the GA interconnected with macropores offers favorable channels for electrolyte transport. Thereby, the specific capacitance of 200 F g−1 (178 C g−1) and 386 F g−1 (170 C g−1) are achieved for GA-Fe2O3 (20 wt% Fe2O3) and GA-NCS (77 wt% NCS), respectively. A coin-type capacitor built with GA-Fe2O3 as negative electrode and GA-NCS as positive electrode delivers a specific capacitance of 93 F g−1 (128 C g−1) at 0.1 A g−1, corresponding to a maximum energy density of 25 Wh kg−1 at a power density of 54 W kg−1. Meanwhile, the ASC also exhibits a good rate capability and a satisfying cycling stability with 72.3 % capacitance retention after cycling at 2 A g−1 for 5000 cycles. These results show great potentials of GA-Fe2O3 and GA-NCS electrodes in electrochemical energy storage.

Insights into the phase transformation of NiCo2S4@rGO for sodium-ion battery electrode

A promising hybrid anode material for sodium ion batteries (SIBs) is designed and synthesized by coating reduced graphene oxide onto NiCo2S4 nanoparticles (denoted as NCS@rGO). An intrinsic 3D micro-mesoporous network is obtained, which can shorten and fasten the access of Na+ diffusion and electron transport, provide sufficient reaction active sites, and enhance structural stability to suppress volume expansion. As a result, as an anode for SIBs, the NCS@rGO electrode delivers reversible capacity of 621 and 532 mAh g−1 at 0.1 and 0.5 A g−1, respectively. A high capacity retention of 95% is obtained at 0.1 A g−1 after 100 cycles. The reaction mechanism of NCS@rGO during charge and discharge has been investigated. The results reveal that the conversion products of NiS2 and CoS2 from the phase transformation of NiCo2S4 are successfully confined with the rGO coating. Furthermore, the NCS@rGO hybrid exhibits a pseudo-capacitive dominated behaviour, which contributes to the measured superior rate capability. This work provides valuable insight into how the phase transformation of NCS@rGO during the charge/discharge process affecting the performance of sodium ion batteries, and this hybrid can be applied as a promising anode for SIBs.

NiCo2S4 nanoparticles grown on reduced graphene oxides for high-performance asymmetric supercapacitors

The nanostructures of reduced graphene oxide (rGO)/NiCo2S4 are prepared using the simple hydrothermal method and the thermal treatment process, which could provide good conductivity and ideal specific surface area. The rGO/NiCo2S4 electrode shows a maximum specific capacitance of 1059 F g−1, excellent rate capability, and good cycle life. Furthermore, the three dimensional structures of rGO/MnO (3D rGO/MnO) are also synthesized by the hydrothermal method and the thermal treatment process, which have the high specific surface area and good conductivity. The rGO/MnO electrode exhibits a maximum specific capacitance of 469 F g−1. A rGO/MnO//rGO/NiCo2S4 asymmetric supercapacitors (ASC) is assembled using 2 M KOH solution as electrolyte, rGO/NiCo2S4 as positive electrode and rGO/MnO as negative electrode. The rGO/MnO//rGO/NiCo2S4 ASC shows an energy density of 38.8 Wh kg−1 at a power density of 0.4 kW kg−1 and a good cycle life, which provides a possibility toward actual application in energy-storage systems.

NiCo2S4 decorated g-C3N4 nanosheets for enhanced photocatalytic hydrogen evolution

Efficient hole-electron pair separation plays a crucial role in enhancing photocatalytic activity of g-C3N4, which usually requires a noble metal cocatalyst. Here we report metallic NiCo2S4 nanoparticles as a cocatalyst and replacement of noble metals to improve the performance of g-C3N4 for photocatalytic hydrogen evolution. NiCo2S4 nanoparticle-modified g-C3N4 has been successfully synthesized. Experimental results indicate that the loading of NiCo2S4 boosts the photocatalytic hydrogen evolution reaction (HER) activity of g-C3N4. The photocatalytic HER of the NiCo2S4/g-C3N4 was investigated using triethanolamine as a sacrificial agent. The 5%-NiCo2S4/g-C3N4 nanocomposite displayed the optimal H2 production rate of 244.7 μmol h−1 g−1, which is about 153 times higher than that of pure g-C3N4. The intimate interface contact between NiCo2S4 and g-C3N4 favors charge separation and is likely responsible for the enhanced photocatalytic activity. This work provides the evidence that NiCo2S4 is a potential cocatalyst for boosting the HER activity of NiCo2S4/g-C3N4 nanocomposite.

Multifunctional reaction interfaces for capture and boost conversion of polysulfide in lithium-sulfur batteries

Lithium-sulfur batteries have gotten a growing number of investigations because of its overwhelming superiority in theoretical energy density and cost. Nevertheless, the application process of lithium-sulfur batteries is severely obstructed by disadvantageous shuttle effect, which arises from the dissolution and migration of intermediate polysulfides and its sluggish conversion kinetics. Herein, we design the conductivity-adsorption-catalysis reaction interface, which is constructed by growing NiCo2S4 nanoparticle on reduced graphene oxide (NiCo2S4@rGO), to afford chemical immobilization and conversion promotion of polysulfides. In this structure, rGO with excellent conductivity can ensure rapid electron transfer and well-distributed NiCo2S4 nanoparticles serve as high-efficiency active sites to anchor polysulfides and accelerate its conversion reaction. Thus, lithium-sulfur batteries with this multifunctional reaction interface deliver improved cycling stability with capacity retention rate of 76% after 500 cycles at 1 C. And a good initial capacity of 776 mAh g−1 is gained under high sulfur loading of 3.6 mg cm−2. This work supplies promising interface design strategies to enhance polysulfides redox kinetics and alleviate shuttle effect for high-performance lithium-sulfur batteries.

A NiCo2S4@N/S–CeO2 composite as an electrocatalytic signal amplification label for aptasensing

Herein, we designed a NiCo2S4@N/S–CeO2 composite with amplified electrocatalytic oxygen reduction (OR) capability by the in situ growth of NiCo2S4 nanoparticles on CeO2 nanospheres with simultaneous doping of nitrogen and sulfur.

Plasma-induced on-surface sulfur vacancies in NiCo2S4 enhance the energy storage performance of supercapatteries

Accurate tuning sulfur vacancy of NiCo2S4 nanoparticles enabled by plasma treatment provides a novel and efficient approach to enhance electrochemical performance of supercapattery.

Synthesis and characterisation of nickel cobalt sulfide nanoparticles by the solvothermal method for dye-sensitized solar cell applications

The aims of this study were to synthesize and characterize a nickel cobalt sulfide (NiCo2S4), namely a ternary transition metal sulfide, by the solvothermal method for DSSC applications. Four samples of NiCo2S4 nanoparticles (NCS1, NCS2, NCS3 and NCS4) were synthesized by varying the amount of thiourea used in the synthesis. The samples were found to have an average crystallite size of 3 nm. The FE-SEM images of the samples show the particles to have uniform spherical shape, with agglomeration into clusters in some places. The presence of Co, Ni and S was confirmed through EDS analysis. From the fingerprint region of the FTIR spectra, the presence of sulfur was confirmed. A peak at 672 cm−1 was observed in the Raman spectra which matches the reported value of 678 cm−1, confirming the formation of NiCo2S4 nanoparticles. The efficiencies of the DSSCs fabricated with NCS2, NCS3 and NCS4 were found to be 0.87, 1.54 and 1.87%. From the results it is concluded that NiCo2S4 can be a candidate for use as a counter electrode in DSSC applications.

NiCo2S4 spheres grown on N,S co-doped rGO with high sulfur vacancies as superior oxygen bifunctional electrocatalysts

Rational design of stable and active bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is desirable but it remains challenging. In this work, NiCo2S4 spheres grown on N,S co-doped reduced graphene oxide sheets with sulfur vacancies (Vs-NiCo2S4/N,S-rGO) have been successfully fabricated through a facile solution method with post heat-treatment. As ORR catalyst, it presents more positive half-wave potential (0.84 V), smaller Tafel slope (43.8 mV dec−1) than that of pure NiCo2S4 nanoparticles (0.59 V and 75.6 mV dec−1) and N,S-rGO (0.54 V and 113.7 mV dec−1) in 0.1 M KOH. As OER catalyst, the Vs-NiCo2S4/N,S-rGO only requires an overpotential of 340 mV to deliver a current density of 10 mA cm−2 in 0.1 M KOH. Significantly, as oxygen bifunctional electrocatalyst, the Vs-NiCo2S4/N,S-rGO provides a smaller potential difference (0.73 V) than that of pristine NiCo2S4 nanoparticles (1.11 V), N,S-rGO (1.36 V) and most non-precious electrocatalysts. The much improved electrochemical performance of the Vs-NiCo2S4/N,S-rGO for both OER and ORR in 0.1 M KOH could be ascribed to considerable high-valence Ni3+ and Co3+ in spinel-type material and sulfur vacancies, which can improve electrical conductivity and increase the exposure of metal active sites, respectively, and thereby facilitate catalytic process. This work provides a feasible strategy to develop high-efficient bifunctional electrocatalysts with promising applications in rechargeable metal-air batteries and fuel cells.

Decoration of Hollow Mesoporous Carbon Spheres by NiCo2S4 Nanoparticles as Electrode Materials for Asymmetric Supercapacitors

In this paper, seasame-ball-like core–shell hollow mesoporous carbon spheres decorated by NiCo2S4 nanoparticles (NiCo2S4/HMCSs) were prepared via a hydrothermal method. The obtained NiCo2S4/HMCSs c...

ZIF-67-derived Co, Ni and S co-doped N-enriched porous carbon polyhedron as an efficient electrocatalyst for oxygen evolution reaction (OER)

Rational fabrication of highly efficient and non-precious metal electrocatalysts for oxygen evolution reaction (OER) are of great importance for renewable energy exploitation to solving the energy crisis and environmental problems. In this paper, we report a novel hybrid nanostructure with Co, Ni and S co-doped N-enriched porous carbon polyhedron (CoNixSy/NCP) via a absorption-pyrolysis-sulfuration strategy derived from zeolitic imidazolate framework-67 (ZIF-67) and explored its electrocatalytic performance for OER. During the synthesis process, Ni2+ is abosrbed within the pores or surface of ZIF-67 and Ni/ZIF-67 can be transformed into the Co and Ni co-doped porous carbon frameworks when it is sulfurazed at 800 °C. NiS2 and NiCo2S4 nanoparticles formed at high temperature are homogeneously dispersed in porous carbon and can activate its electrocatalytic performance. The porous carbon can enhance the electrochemical surface area and charge transfer efficiency. Benefiting from the synergistic effects between highly active NiS2, NiCo2S4, and porous carbon, CoNixSy/NCP electrocatalyst exhibits excellent electrocatalytic performance. The results show that CoNixSy/NCP also exhibits a potential as low as 1.51 V to achieve 10 mA/cm2 current density and extremely stability towards OER. The good electrocatalytic activity of CoNixSy/NCP further suggest its great potential as an efficient eletctocatalyst for sustainable energy applications.

Highly dispersive NiCo2S4 nanoparticles anchored on nitrogen-doped carbon nanofibers for efficient hydrogen evolution reaction

To solve the energy crisis problem, many efforts have been devoted to develop clean and sustainable alternatives to fossil fuels. Among varieties of pathways to obtain clean energy, electrochemical water splitting is a promising approach. Herein, we had successfully synthesized the NiCo2S4@porous nitrogen-doped carbon nanofibers (NiCo2S4@NCNF) nanocomposite via three successive steps consisted of in-situ oxidative polymerization, calcination, and solvothermal sulfuration reaction processes. The effect of controlled molar ratios to electrocatalytic performance was studied in detail. The optimized NiCo2S4@NCNF nanocomposite exhibits superior electrocatalytic activity for hydrogen evolution reaction with a small overpotential of 117 mV to drive a current density of 10 mA cm−2. More importantly, it exhibits similar electrocatalytic activity to the initial state even after successive cyclic voltammetry scan for 3000 cycles, indicating its excellent long-term stability. The superior electrochemical performance is attributed to the developed three-dimensional (3D) network nanostructure derived from bacterial cellulose nanofibers, the highly conductive porous nitrogen-doped carbon nanofibers, and the synergistic effect between metal Ni and Co of NiCo2S4. This study permits a new pathway to design efficient electrocatalysts based on eco-friendly materials for the production of clean hydrogen energy.

Self-supporting graphene aerogel electrode intensified by NiCo2S4 nanoparticles for asymmetric supercapacitor

Transition bimetallic nickel cobalt sulfide has attracted extensive attention as a novel electrode for supercapacitors. In this study, facial solvothermal method is applied to prepare NiCo2S4 nanoparticles and nanosheets immobilized on graphene aerogel (NiCo2S4/GA). The microstructure of NiCo2S4 is significantly affected by altering the pH of the solution. Typically, the uniformly dispersed NiCo2S4 nanoparticles with diameter 25.94 nm are successfully grown on GA when the solution pH is 8.2. The NiCo2S4/GA electrode delivers an improved specific capacitance of 704.34 F g−1 at 1 A g−1, and maintains a favorable rate capability of 60.1% at 10 A g−1. Moreover, 80.3% of the initial specific capacitance is maintained after 1500 cycles at 2 A g−1. The impressive electrochemical performance results from the NiCo2S4 with high capacitance and GA with three-dimensional porous nanostructure, which can not only reduce the contact resistance but also efficiently shorten the electron and ion transport path. Furthermore, the solid-state asymmetric supercapacitor device based on NiCo2S4/GA electrode can present energy density of 20.9 Wh kg−1 at a power density of 800.2 W kg−1 and desirable cycling stability, showing the great application potential in the field of energy storage devices.

A NiCo2S4 /hierarchical porous carbon for high performance asymmetrical supercapacitor

A NiCo2S4 nanoparticles composite, in-situ grown on rice husk hierarchical porous carbon, is synthesized through a facile one-step hydrothermal method for energy storage. The NiCo2S4 nanoparticles with a size of 20 ± 10 nm are homogeneously distributed on the carbon matrix, leading to a high material utilization and high capacity, significantly outperformed the pure NiCo2S4. The chemical bonds of C-O-Co and C-O-Ni between the NiCo2S4 nanoparticles and the carbon matrix not only result in a superior power density, but also improve the cycling stability. An asymmetrical supercapacitor is assembled using the composite material and commercial YP-50 activated carbon and shows high energy density, high power density and excellent cycling stability. The hydrothermal method can be extended to synthesize other composite materials for energy storage devices.

NiCo2S4 nanoparticles anchoring on polypyrrole nanotubes for high-performance supercapacitor electrodes

To solve the inevitable aggregation and the low cycling stability of NiCo2S4 electrode materials, herein NiCo2S4 nanoparticles anchoring onto polypyrrole nanotubes were synthesized by a hydrothermal method. The obtained NiCo2S4/polypyrrole nanotubes composites exhibit a high specific capacitance of 1705Fg−1 at 1 A g−1, and remarkable rate performance of 747.6Fg−1 at 20 A g−1. Furthermore, the assembled asymmetric supercapacitor using NiCo2S4/polypyrrole nanotubes as a positive electrode and activated carbons as a negative electrode delivers a high energy density of 52.5Whkg−1 at a power density of 562.5Wkg−1, and excellent cycling stability with 83.3% retention after 5000cycles. The excellent electrochemical performance of NiCo2S4/polypyrrole nanotubes can be attributed to the high conductivity of polypyrrole nanotubes, and the key assistant effects of polypyrrole nanotubes which impede the aggregation of NiCo2S4 and improve the exposed active sites for redox reaction. The results demonstrate that NiCo2S4/polypyrrole nanotubes are a promising electrode material for supercapacitors.

Novel dealloying-fabricated NiCo2S4 nanoparticles with excellent cycling performance for supercapacitors

In this work, NiCo2S4 nanoparticles for supercapacitors are successfully synthesized with a top-down strategy, using a novel dealloying method with an ion exchange reaction. The surface morphology and x-ray diffraction investigations demonstrated that NiCo2S4 nanoparticles are interconnected by ligaments of the synthesized sample. The dealloyed NiCo2S4 shows an enhanced electrochemical performance of about 1132.5 F g−1 at 0.5 A g−1; kinetic analysis implies a surface-controlled contribution from NiCo2S4 (53.86% capacitive contributions). Notably, the NiCo2S4//AC (active carbon) device displays a comparatively high energy density (22.83 Wh kg−1), maximum power density (1327.1 W kg−1) and superior cycling performance (capacitance retention of 108% after 30 000 cycles).

NiCo2S4 nanocores in-situ encapsulated in graphene sheets as anode materials for lithium-ion batteries

Bimetallic sulfides were extensively studied as an advanced electrode material for lithium-ion batteries because of their high conductivity and superior capacity compared to metal oxides. We herein have successfully fabricated ultrafine NiCo2S4 nanocores in-situ encapsulated in graphene sheets (NiCo2S4@GS) with three-dimensional porous network structures through a cation adsorption process and subsequent hydrothermal-annealing reaction. In the NiCo2S4@graphene sheets nanohybrids, graphene sheets with abundant mesoporous network structure can be served as a conductive matrix and also be a protective buffer layer to suppress the volume expansion of NiCo2S4 nanoparticles. The NiCo2S4@GS-1 electrodes deliver a high reversible capacity of 813 mAh g−1 upon 200 cycles at 0.2 A g−1, ultralong cycling life of 535 mAh g−1 upon 1000 cycles at 2 A g−1, and excellent rate capability. Additionally, the advanced button-type full batteries were assembled via coupling NiCo2S4@GS-1 anodes with commercial LiFePO4 cathodes showing superior cycle stability and practicability. This work points out an innovative and scalable strategy for preparing composite electrode materials for lithium-ion batteries.

A novel H2O2 electrochemical sensor based on NiCo2S4 functionalized reduced graphene oxide

In this work, we successfully prepared NiCo2S4 nanoparticles decorated reduced graphene oxide through a facile method. The obtained NiCo2S4/rGO hybrids could be modified on a glassy carbon electrode to construct a highly sensitive non−enzymatic H2O2 sensor. The morphology and structure of the obtained NiCo2S4/rGO were characterized by transmission electron microscopy (TEM), X−ray powder diffraction (XRD) and X−ray photoelectron spectroscopy (XPS). The electrochemical performance of the NiCo2S4/rGO hybrids toward the reduction of H2O2 was reflected through the cyclic voltammetry and chronoamperometry data. The hybrids exhibit a fast response time within 5 s, wide linear range of 0.025–11.25 mM, high sensitivity of 118.5 μA mM−1 cm−2, as well as low detection limit of 0.19 μM. Such results demonstrate NiCo2S4/rGO hybrids is a promising candidate for the quantitative detection of H2O2.

Structural and chemical synergistic effect of NiCo2S4 nanoparticles and carbon cloth for high performance binder-free asymmetric supercapacitors

A facial solvothermal method is used to synthesize NiCo2S4 nanoparticles on carbon cloth (CC) to investigate the synergistic effect of transition metal sulfide and carbon substrates on the electrochemical performance in supercapacitors. The results demonstrate that the integrated binder-free NiCo2S4/CC electrode achieved a specific capacitance of 1379 F g−1 at 1 A g−1, and high rate capability of 82% when the current density increase to 50 A g−1, which is 13% and 35% higher than that of pristine NiCo2S4 counterpart. Detailed electrochemical kinetic analysis reveals that the proportion of surface capacitive effect of the hybrid electrode is higher than that of NiCo2S4 electrode at various scan rates due to the introduction of CC. CC substrate can provide a highway for electrolyte ions and electrons, facilitate the reaction kinetics, and shorten the diffusion distances for redox reaction, leading to improved performance of pseudocapacitive NiCo2S4. In addition, the as-fabricated asymmetric supercapacitors (ASC) based on NiCo2S4/CC//CNF electrodes demonstrate a high energy density of 41.28 W h kg−1 at a power density of 1564 W kg−1, along with long-term cycling performance and high rate stability.

Improving electrochemical activity of activated carbon derived from popcorn by NiCo2S4 nanoparticle coating

We report a popcorn-derived activated carbon (PCs) from maize grains. Dispersed NiCo2S4 nanoparticles of dozens of nanometers in diameter are anchored onto the PC surface to yield PCs/NiCo2S4 composites. The adhesion of NiCo2S4 nanoparticles to the porous carbon substrate provides the PCs/NiCo2S4 composite electrode with an improved electrochemical performance. The highly electroconductive PCs substrate with porous structure and combination with dispersive NiCo2S4 nanoparticles, yields PCs/NiCo2S4 composites with a high specific capacitance of 605.2 F g−1 at the current density of 0.5 A g−1 in a voltage range of −0.1 to 0.4 V in 6 M KOH electrolyte, and an outstanding capacitance conservation of 91.3% after 5000 galvanostatic charge/discharge cycling. Moreover, the asymmetric supercapacitor demonstrates high energy density of 23.3 W h kg−1 at the power density of 335.8 W kg−1, and an excellent cycling stability of 92.7% capacitance retention after 5000 cycles. This research supplies a novel method to exploit biomass-based electrode material candidates for promising application on high-performance supercapacitors.