NiS Nanoparticles Research Articles

Controllable Synthesis of NiS/rGO Hybrid Composite: An Excellent Counter Electrode for Dye Sensitized Solar Cell

We have synthesized an efficient NiS anchored reduced graphene oxide (rGO) nanosheet composites were by a facile hydrothermal route and served as the efficient counter electrodes (CE) for dye-sensitized solar cells (DSSCs). XRD and FESEM results suggest that the electrodes were well crystalline with formation of individual spherical like with homogeneous nanoparticles sizes in the range of 40–30 nm, which is distributed throughout the rGO sheet. The UV–Vis DRS suggest that the absorption edge of all the electrodes were in the visible light region, further it was shifted in the longer wavelength side with the increase of rGO content. The separation, transfer and recombination behavior of the photogenerated charge carriers were analyzed by PL spectra. The NiS/rGO CE produces a power conversion efficiency of 9.25%, which is higher than that (5.21%) for the DSSC with the bare CE. The enhanced efficiency of NiS/rGO hybrid composite is due to reduction of the triiodide caused by the synergistic effects between the extremely catalytic NiS nanoparticles and high electrical conductive nature of rGO sheet.

0D/2D NiS2/V-MXene composite for electrocatalytic H2 evolution

As a member of the family of so-called MXenes, two-dimensional vanadium carbide (V2CTx, denoted as V-MXene) used in electrocatalytic hydrogen evolution reaction (HER) is still in the stage of theoretical study without significant experimental exploration. Here, we present the theoretical and experimental studies on the intrinsic structural and electrochemical properties of V-MXene-based hybrid (NiS2/V-MXene) to verify the possibility of using it as a potential electrocatalyst for HER. For the purpose of comparison, the most popular titanium carbide (Ti3C2Tx, denoted as Ti-MXene) is studied too. As a proof of concept, NiS2/V-MXene and NiS2/Ti-MXene, are designed, prepared and experimentally explored. As expected, NiS2/V-MXene is proved to be a better electrocatalyst for HER than NiS2/Ti-MXene due to its faster electronic transfer and favorable interactions. The tight cover of NiS2 nanoparticles not only prevents V-MXene from restacking but also favors the exposure of extra active sites to accelerate the electrolysis process. Such a unique sandwich-like architecture is highly preferable to provide larger contact interface and more pathways for electron migration and mass diffusion during the electrolysis. Meanwhile, the predicted electron transfer from V-MXene to NiS2 is confirmed experimentally using X-ray photoelectron spectroscopy. This research may provide a guide for the design and development of V-MXene-based electrocatalysts for HER, and expand their potential applications.

Solvothermally Doping NiS2 Nanoparticles on Carbon with Ferric Ions for Efficient Oxygen Evolution Catalysis

Exploring efficient non-precious metal based electrocatalysts for the oxygen evolution reaction (OER) is a prerequisite to implement the widespread application of a water electrolyzer and metal-air batteries. Herein, Fe-doped NiS2 nanoparticles on a carbon matrix (Fe-NiS2/C) are facilely prepared via a two-step solvothermal process, where Ni-containing metal organic frameworks (Ni-MOFs) are vulcanized in situ and carbonized by a solvothermal method to form abundant NiS2 nanoparticles homogeneously distributed on a carbon matrix (NiS2/C), followed by doping with ferric ions via a similar solvothermal treatment. The resulting Fe-NiS2/C nanoparticle composites show a rougher surface than the NiS2/C parent, likely due to the formation of more structural defects after ferric ion doping, which maximizes the exposure of active sites. Moreover, ferric ion doping can also regulate the surface electronic state to reduce the activation energy barrier for OER on NiS2/C sample. With these merits, the best sample Fe-NiS2/C-30 only requires a potential of +1.486 V (vs. RHE) to reach an OER current density of 10 mA cm−2 and can retain 96.85% of its initial current after continuous working for about 10 h in 1.0 M KOH aqueous solution, along with a small Tafel slope of 45.66 mV/dec, outperforming a commercial RuO2 catalyst. The results in this work enrich the method to tailor the catalytic activity of transition metal sulfides for electrochemical energy technologies.

Nitrogen-doped carbon shell-confined Ni3S2 composite nanosheets derived from Ni-MOF for high performance sodium-ion battery anodes

Nickel sulfides are suitable anode materials for sodium-ion batteries (SIBs) because of their moderate cost and high theoretical capacity. Nevertheless, low cycling stability and rate performance caused by volume expansion and inferior electronic conductivity during the charge/discharge process still hamper their development. Herein, Ni3S2 nanoparticles uniformly embedded in N-doped carbon nanosheets (Ni3S2@C) are synthesized by sulfuration of a Ni-based metal-organic framework (Ni-MOF), followed by coating with polypyrrole (PPy). The PPy protects Ni3S2 particles from aggregation, and is converted to N-doped carbon shell during the annealing process. The nano-sized structure accelerates reaction kinetics and minimizes stress/strain caused by volume changes. The N-doped carbon nanosheets connect the transmission pathway of the electrons, and buffer the volume change during the electrochemical reaction. As expected, NiSx@C-600 delivers superior sodium storage performance with a high discharge capacity of 432.8 mA h g−1 at 0.2 A g−1 over 100 cycles and remarkable rate capacity of 371.6 mA h g−1 at a high rate of 6.4 A g−1. To the best of our knowledge, the obtained nanosheets exhibit the best rate performance among current Ni3S2 composites. The proposed method for enhancing conductivity and doping heteroatom by using PPy provides a novel insight to design SIB anodes with superior performance.

In situ observation of NiS nanoparticles depositing on single TiO2 mesocrystal for enhanced photocatalytic hydrogen evolution activity

For photocatalysis, clarifications of charge carrier migration route and kinetics on individual particles by photoluminescence (PL) are of great importance because they play significant roles on unveiling the precise information of structure-activity relationships and closely relate to the photocatalytic activities of those semiconductors on targeted functions. Here, photodeposition process of NiS nanoparticles on single TiO2 mesocrystal (TMC) as co-catalyst is in situ monitored by PL images and spectra using a confocal single-particle PL microscopy, which provides straightforward results on understanding the photoexcited electrons transfer in both individual TMC and TMC/NiS nanoparticles. Through the changes in PL intensity and decay lifetime, preferential trapping site for NiS nanoparticles on TMC is identified and efficient electron interfacial migration from TMC to NiS nanoparticles is demonstrated, which lead to an almost 71 folds enhancement on the photocatalytic H2 evolution under 365-nm photoirradiation compared to pure TMC particles.

N-doped reduced graphene oxide decorated NiSe2 nanoparticles for high-performance asymmetric supercapacitors

This work reports the preparation of N-doped reduced graphene oxide decorated NiSe2 nanoparticles (N-rGO/NiSe2) in the presence of different amount of graphene oxide reactant by a simple two-step process, which contains hydrothermal preparation of Ni(OH)2 precursor and then solvothermal synthesis of N-rGO/NiSe2 composites with different content of N-rGO. The as-prepared N-rGO/NiSe2 composites is characterized by power X-ray diffraction, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and N2 adsorption–desorption isotherm. The results show that N-rGO acts as supporter of NiSe2 nanoparticles to prevent them from aggregation, leading to the increase in specific surface area and electrical conductivity of material. The optimized N-rGO/NiSe2 composite can deliver high specific capacitance of 2451.4 F g−1 at a current density of 1 A g−1. Using activated carbon (AC) as negative electrode and the optimized N-rGO/NiSe2 composite as positive electrode, an asymmetric supercapacitor is constructed. This fabricated asymmetric supercapacitor can work stably under the potential window of 0–1.6 V, and presents the maximum energy density of 40.5 Wh kg−1 at a power density of 841.5 W kg−1. Moreover, the N-rGO/NiSe2//AC asymmetric supercapacitor exhibits good cyclic stability.

Metallic Mo2C anchored pyrrolic-N induced N-CNTs/NiS2 for efficient overall water electrolysis

Transition metal disulfides have shown promising catalytic activity, while carbides possess high stability toward water electrocatalysis. It is an ideal way to develop high-performance electrocatalysts with enhanced activity and stability by combining the two compounds together. Herein, we present a new strategy to promote the sulfidation process of Ni nanoparticles by modifying with MoxC, which can increase the ratio of pyrrolic-N and pyridine-N. Interestingly, the increase of pyrrolic-N can further promote the metal Ni completely sulfurized into NiS2 nanoparticles. The as-synthesized material of NiS2 nanoparticles coated with self-grown carbon nanotubes modified by Mo2C can serve as bifunctional electrode, which achieves a current density of 10 mA cm−2 at a voltage of 1.52 V to generate H2 and O2 gases in alkaline media. Moreover, it can maintain 24 h stability at different current densities, which is more stable than N-CNTs/NiS2-Ni without Mo element. This finding provides a new method and idea for the development of new composite electrocatalysts toward more efficient water splitting.

Efficient photocatalytic H2 evolution using NiS/ZnIn2S4 heterostructures with enhanced charge separation and interfacial charge transfer

The effect of multidimensional heterostructures on charge transfer and charge separation is intriguing in photocatalytic applications. Herein, NiS/ZnIn2S4 heterostructures with tailorable composition, tunable light absorption, and controllable band gap were successfully prepared by a two-step method to show uniform NiS nanoparticles with an average size of 10 nm loaded homogeneously on porous ZnIn2S4 nanosheets. Consequently, NiS/ZnIn2S4 heterostructures have markedly enhanced light absorption and efficient photocatalytic efficiency, reaching the hydrogen evolution rate of 5.0 μmol h−1 under the light irradiation at 420 nm, to be approximately three times higher than that of pure ZnIn2S4. The enhanced photocatalytic efficiency results from faster charge transfer and more efficient photogenerated electron-hole separation under beneficial band alignment. The results shed light on how the photocatalytic reaction occurs at the interface between NiS and ZnIn2S4, and can open a new avenue for synthesizing efficient photocatalysts.

Large-scale synthesis of NiS@N and S co-doped carbon mesoporous tubule as high performance anode for lithium-ion battery

The simple and large-scale synthesis of metal sulfides@heteroatom-doped carbon tubules with high lithium storage performance is seldom reported. In this work, mesoporous NiS@N and S co-doped carbon (NiS@NSC) tubules were firstly prepared by nickel salt impregnation and subsequently calcination using absorbent cotton as template. The crystalline NiS nanoparticles with an average particle size of about 90 nm are uniformly embedded in the mesoporous tubular N and S co-doped carbon skeleton. The BET specific surface area is 200.8 m2 g−1 and the uniform narrow mesopore size distributes centered at 2.32 nm. As anode for lithium-ion batteries, it displays good cycling stability and rate capability, which retains a reversible capacity of 715.9 mA h g−1 after 200 cycles at 0.1 A g−1, and even at a high current density of 5 A g−1 the specific discharge capacity can retain 411.1 mA h g−1, which is higher than for most of the reported NiS@C composites. The good electrochemical performances are mainly attributed to the inherent characteristics of NiS@NSC hollow tubules, involving uniform mesopores, large specific surface area and highly conductive N and S co-doped carbon skeleton.

Improved charge separation of NiS nanoparticles modified defect-engineered black TiO2 hollow nanotubes for boosting solar-driven photocatalytic H2 evolution

NiS nanoparticles modified black TiO2 hollow nanotubes (NBTNs) are successfully synthesized via surface hydrogenation and the facile solvothermal method. The unique structure with intensified surface and interface characteristics endow NBTNs with more catalytic sites, and increase charge carrier separation efficiency with an extended charge lifetime, overwhelmingly promoting its photocatalytic performance. The resultant NBTNs possess a relatively high surface area and pore size of ∼89 m2 g−1 and ∼9.8 nm, respectively. The resultant NBTNs exhibit an excellent solar-driven photocatalytic hydrogen rate (3.17 mmol h−1 g−1), which is almost as high as that of Pt as cocatalyst, in which the apparent quantum yield of 5.4% (420 nm) is recorded for the NBTNs sample. Moreover, the turnover number can be up to 116 000 within 48 h and the turnover frequency is 2400 for NiS. This novel strategy could provide a better understanding of cocatalyst photocatalytic mechanisms, and a scheme simultaneously regulating the morphology and structure of photocatalysts for promoting H2 generation.

Solvent-mediated crystalline phases of NixSy anchored on rGO sheets as electrocatalysts for hydrogen evolution application

A facile, one-pot solvent-mediated hydrothermal process was adopted to prepare nickel sulfide nanoparticles decorated on reduced graphene oxide (NixSy/rGO) as electrocatalysts for hydrogen evolution reaction (HER). The designed solvent (ethylene glycol and deionized water) played a decisive role in controlling both crystalline phase and morphology of NixSy/rGO composites, leading to pure [Formula: see text]-NiS nanoparticles uniformly distributed on rGO sheets under suitable volume ratio of ethylene glycol and deionized water (2:1). The optimized [Formula: see text]-NiS/rGO showed prominent HER catalytic performance with a rather small Tafel slope of 93[Formula: see text]mV/decade and prominent current density of 10[Formula: see text]mA/cm2 at the overpotential of 177[Formula: see text]mV in alkaline environments when compared to pristine [Formula: see text]-NiS and NiS2/rGO catalysts. The excellent catalytic performance and long-term durability even after 8000 cycles confirmed the potential of [Formula: see text]-NiS/rGO composites as efficient electrocatalysts for HER in the alkaline media.

Synthesis and characterization of (Co, Fe, Ni)9 S8 nanocomposite supported on reduced graphene oxide as an efficient and stable electrocatalyst for methanol electrooxidation toward DMFC

In this study, Co4S3, Fe3S4, and NiS nanoparticles as a nanocomposite in the form of a new composite called (CoFeNi)9 S8 (CFNS) were synthesized by a facile hydrothermal method. Then, graphene oxide supported (CoFeNi)9 S8 nanoparticles (CFNS/rGO) were prepared and methanol oxidation reaction evaluated on CFNS/rGO electrocatalyst. X-ray diffraction and energy dispersive X-ray spectroscopy analysis were used to investigate the structure and phase identification of electrocatalyst. Homogenous dispersion of CFNS nanoparticles on rGO was confirmed by FESEM and HRTEM images. The electrocatalytic activity of CFNS/rGO hybrid was assessed by cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy techniques. The CFNS/rGO exhibited high electrocatalytic activity for methanol electrooxidation in alkaline media. The significant activity of CFNS/rGO assigned to synergistic effects between Co, Fe, and Ni, suitable dispersion of CFNS nanoparticles on rGO, high surface area, and porous structure of rGO that comforts the diffusion of methanol. Therefore, the CFNS/rGO catalyst has enough potential for application in the direct methanol fuel cell.

Porous Ni3S4/C aerogels derived from carrageenan-Ni hydrogels for high-performance sodium-ion batteries anode

Nickel sulfide (Ni3S4) has been recognized as one of the most advanced anode materials for sodium-ion batteries (SIBs) on account of its cost effectiveness, commendable redox reversibility and high theoretical capability. However, like other metal sulfide (MS) anodes, the Ni3S4 suffers from poor cycle life and inferior rate capability owing to large volume changes during the repeated Na+ de/insertion process and unsatisfied electronic conductivity. Herein, we fabricated porous Ni3S4/carbon aerogels (Ni3S4/CAs) using carrageenan-Ni hydrogels as the precursor via the pyrolysis route. The sulfate groups located uniformity and confinement for Ni2+ ions in carrageenan double-helix structures converted into uniform Ni3S4 nanoparticles (NPs) embedded in porous carbon through the decomposition. Remarkably, the as-prepared Ni3S4/CAs-1 sample as the anode material for SIBs exhibits a high reversible capacity of 297 mAh g−1 at a current density of 1 A g−1 after 100 cycles. This work develops a facile way to synthesize Ni3S4/CAs as a promising anode material for SIBs from marine biomass resources.

Highly dispersed ultrasmall NiS2 nanoparticles in porous carbon nanofiber anodes for sodium ion batteries.

Although sodium-ion batteries (SIBs) show attractive advantages over current dominant lithium ion batteries (LIBs), they still face great challenges in addressing the issues of low capacity and poor cycling stability. We herein report the synthesis of a nanohybrid of ultrasmall NiS2 nanoparticles embedded in porous carbon nanofibers (NiS2NP/p-CNF), which is implemented by an electrospinning process accompanied by further sulfide treatment. The highly dispersed NiS2 nanoparticles, coupled with the highly conductive porous nanofiber structure, endow the hybrids with favorable properties and structure for reducing the effects of volume expansion, providing a fast mass transport channel, and facilitating electron transfer. Systematic electrochemical studies verify that NiS2NP/p-CNF, when studied as an SIB anode, exhibits high performance with an excellent specific capacity (500 mA h g-1 at 0.1 A g-1) and a competitive rate capability, maintaining 200 mA h g-1 at 2.0 A g-1, besides a long-term stability for 1000 cycles. The NiS2NP/p-CNF nanofibers provide a huge potential for the development of massive sodium storage.

Enhanced Photoelectrochemical and Photocatalytic Properties of CdS Nanowires Decorated with Ni3S2 Nanoparticles under Visible Light Irradiation

Ni3S2/CdS nanocomposites based on zero-dimensional Ni3S2 nanoparticles (NPs) and one-dimensional CdS nanowires (NWs) were synthesized via a two-step solvothermal approach. These nanocomposites were characterized using a combination of experimental techniques, including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, and photoelectrochemistry method. The Ni3S2/CdS nanocomposites exhibit much higher photocatalytic hydrogen evolution activity than individual CdS NWs or Ni3S2 NPs under visible light irradiation (λ ≥ 400 nm) from water. Photoelectrochemical (PEC) and photocatalytic properties of the Ni3S2/CdS nanocomposites were investigated as a function of the molar ratio between Ni3S2 and CdS. In addition, ultrafast transient absorption (TA) spectroscopy was employed to probe the charge carrier dynamics, which is about four times shorter in 10%-Ni3S2/CdS than pure CdS NWs. These results suggest efficient charge transfer between CdS and Ni3S2 at the interface, which is desired for PEC and photocatalytic applications.

Metal chelate induced in situ wrapping of Ni3S2 nanoparticles into N, S-codoped carbon networks for highly efficient sodium storage

Metal-dithiooxamide chelate derived Ni3S2 nanoparticles wrapped in N, S codoped carbon networks exhibit excellent sodium storage performance.

Tuning the coupling interface of ultrathin Ni3S2@NiV-LDH heterogeneous nanosheet electrocatalysts for improved overall water splitting.

Tuning the coupling interface of a heterostructured catalyst is an effective approach to achieve abundant surface catalytic active sites and strong electronic interactions among active materials for improving electrocatalytic water splitting performance. Herein, we report a novel heterogeneous catalyst comprising Ni3S2 nanoparticles embedded in ultrathin NiV-layered double hydroxide nanosheet arrays supported on nickel foam, denoted as Ni3S2@NiV-LDH/NF. We demonstrate that the active edge-state length and the surface chemical state of such NiV-LDH-based heterostructures are well modulated by tailoring the coupling interfaces, resulting in the exposure of more catalytic reaction sites and enhancement of the electronic interactions between NiV-LDH and Ni3S2, thus greatly promoting the water dissociation kinetics. As expected, the optimized Ni3S2@NiV-LDH/NF heterostructures exhibit outstanding electrocatalytic activity for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with an extremely low overpotential of 126 mV and 190 mV to deliver 10 mA cm-2 for the HER and OER without iR compensation in alkaline media, respectively. More importantly, Ni3S2@NiV-LDH/NF simultaneously functioned as both the anode and cathode for water splitting to yield a current density of 10 mA cm-2 at a cell voltage of only 1.53 V with an outstanding durability for 160 h. This work provides a new insight into the regulation of the coupling interface for obtaining highly active heterostructured catalysts for overall water splitting.

One-Pot Electrodeposition of NiS Nanoparticles as an Efficient Electrode for Nonenzymatic H2O2 and Glucose Sensors

In this paper, a new and one-pot electrodeposition method was expanded for the preparation of NiS nanoparticles-based electrochemical biosensor using metal-ion complexes as a precursor. Thioacetamide was used to control the production rate of NiS nanoparticles for the first time. The proposed electrochemical sensor was characterized by energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscope (FESEM), cyclic voltammograms (CV), and electrochemical impedance spectra (EIS). Experiment parameters were optimized. Under the optimized condition, the prepared NiS-based biosensor exhibited excellent electrocatalytic oxidation of H2O2 and glucose due to their small size. It provided fast and sensitive strategy for detecting H2O2 and glucose in the range of 1–5000 and 1–1000[Formula: see text][Formula: see text]M. The detection limit of 0.257 and 0.3[Formula: see text][Formula: see text]M was obtained for H2O2 and glucose. The mechanisms were also analyzed. The proposed biosensor exhibited excellent anti-interference and repeatability. Furthermore, it was applied in the actual sample analysis, such as human blood serum.

Preparation of nickel selenide by pulsed-voltage electrodeposition and its application as a highly-efficient electrocatalyst at counter electrodes of quantum-dot sensitized solar cells

We fabricate the nickel selenide thin films on fluorine-doped tin oxide conducting glass subtract using pulsed-voltage electrodeposition method for counter electrodes in quantum-dot-sensitized solar cells. The novelty of this work is nickel selenides are prepared by PVE significantly differs from the traditional continuous-voltage electrodeposition in morphology, compositions, and electrocatalytic activities. In general, NiSe2-PVE films consist of clusters with crystalline NiSe2 nanoparticles which remain nanoporous because application of anodic bias during pulsed electrodeposition enables diffusion layer of H2SeO3 recover from the deposition. The subsequent short cathodic bias not only facilitates new nucleation of nickel selenide but also hinders grain growth. In contrast, Ni3Se2-CVE film consists dense larger Ni3Se2 grains with surface microcracks attributed to continuous grain growth and accumulated film stress. Hence, NiSe2-PVE enhances electrocatalytic activity in polysulfide electrolyte in an effective manner when compare to Ni3Se2-CVE, owing to significantly more electrocatalytic active sites and enhance charge and mass transports. As an outcome, QDSSC with NiSe2-PVE CE achieve significantly higher power conversion efficiency of 4.46% than those of cells with Pt (2.62%) and Ni3Se2-CVE (2.63%) CEs. Furthermore, electrochemical stability in polysulfide electrolyte medium is reasonably high.

Self-Supported NiSe/Ni Foam: An Efficient 3D Electrode for High-Performance Supercapacitors

Three-dimensional (3D) mixed phases NiSe nanoparticles growing on the nickel foam were synthesized via a simple one-step hydrothermal method. A series of experiments were carried out to control the morphology by adjusting the amount of selenium in the synthetic reaction. Meanwhile, the as-prepared novel column-acicular structure NiSe exist three advantages including ideal electrical conductivity, high specific capacity and high cycling stability. It delivered a high capacitance of 10.8[Formula: see text]F[Formula: see text]cm[Formula: see text] at a current density[Formula: see text] of 5[Formula: see text]mA[Formula: see text]cm[Formula: see text]. An electrochemical capacitor device operating at 1.6[Formula: see text]V was then constructed using NiSe/NF and activated carbon (AC) as positive and negative electrodes. Moreover, the device showed high energy density of 31[Formula: see text]W[Formula: see text]h[Formula: see text]kg[Formula: see text] at a power density of 0.81[Formula: see text]kW[Formula: see text]kg[Formula: see text], as well as good cycling stability (77% retention after 1500 cycles).