Carbon coated nickel sulfide/reduced graphene oxide nanocomposites: facile synthesis and excellent supercapacitor performance

Overview of recent developments in carbon-based nanocomposites for supercapacitor applications

Energy storage devices are recognized as environmentally friendly technologies. Supercapacitors, known for their high cycle stability, have been proposed as potential alternatives to fossil fuels. Recent studies have focused on selecting suitable electrode materials to achieve energy storage systems with high stability, high specific capacity, and biocompatibility. In particular, carbon-based electrode materials, such as graphene oxide, activated carbon, carbon nanotubes, and carbon-based quantum dots, have attracted considerable attention due to their intrinsic properties, such as high conductivity and stability. However, carbon materials alone exhibit limitations, such as low energy density and low specific capacitance. To address this limitation, the synergistic effect of carbon materials has been combined with other electroactive materials to develop electrode materials with enhanced supercapacitor properties. The present study also investigates the supercapacitor performance of carbon-based nanocomposites. It examines the effect of each carbon material (AC, CNT, GO, rGO) on improving the performance of other electroactive materials, including metal oxides, metal sulfides, MXenes, MOFs, and conductive polymers. This study provides valuable insights for further studies on carbon-based electrode materials for supercapacitor applications.

Advanced Carbon-Nickel Sulfide Hybrid Nanostructures: Extending the Limits of Battery-Type Electrodes for Redox-Based Supercapacitor Applications

Transition-metal sulfides combined with conductive carbon nanostructures are considered promising electrode materials for redox-based supercapacitors due to their high specific capacity. However, the low rate capability of these electrodes, still considered "battery-type" electrodes, presents an obstacle for general use. In this work, we demonstrate a successful and fast fabrication process of metal sulfide-carbon nanostructures ideal for charge-storage electrodes with ultra-high capacity and outstanding rate capability. The novel hybrid binder-free electrode material consists of a vertically aligned carbon nanotube (VCN), terminated by a nanosized single-crystal metallic Ni grain; Ni is covered by a nickel nitride (Ni₃N) interlayer and topped by trinickel disulfide (Ni₃S₂, heazlewoodite). Thus, the electrode is formed by a Ni₃S₂/Ni₃N/Ni@NVCN architecture with a unique broccoli-like morphology. Electrochemical measurements show that these hybrid binder-free electrodes exhibit one of the best electrochemical performances compared to the other reported Ni₃S₂-based electrodes, evidencing an ultra-high specific capacity (856.3 C g^-1 at 3 A g^-1), outstanding rate capability (77.2% retention at 13 A g^-1), and excellent cycling stability (83% retention after 4000 cycles at 13 A g^-1). The remarkable electrochemical performance of the binder-free Ni₃S₂/Ni₃N/Ni@NVCN electrodes is a significant step forward, improving rate capability and capacity for redox-based supercapacitor applications.

The high energy supercapacitor from rGO/Ni(OH)2/PANI nanocomposite with methane sulfonic acid as dopant

The low energy densities of supercapacitors limit their utilization as energy storage and energy conversion devices. To overcome this limitation, here we present a ternary nanocomposite of reduced graphene oxide (rGO)/nickel hydroxide (Ni(OH)₂/polyaniline (PANI), with methane sulfonic acid as dopant, having weight percentages of 14%:14%:72% (G14NP), respectively, as an electrode material for supercapacitor. With 1 M sulfuric acid (H₂SO₄) as the electrolyte, the supercapacitor yields a high energy density of 120.48 W h kg^-1, comparable with those of Li-ion batteries. The G14NP also exhibits good electrochemical performance with a specific capacitance of 602.40 F g^-1 and a power density of 2584.83 W kg^-1, at a current density of 1 A g^-1. The G14NP also exhibits a promising stability of its electrochemical performances even after 16,500 cycles at a potential scan of 400 mV s^-1. Remarkably, the composite performs exceptionally well at a potential window available in an aqueous electrolyte. The sustainability to high current loading while charging and its power backup application is satisfactorily demonstrated, by charging with a commercial 9 V battery.

Facile One-Step Synthesis and Enhanced Optical Nonlinearity of Graphene-γMnS

Graphene-γMnS were prepared by facile one-step hydrothermal method. Structures and properties of samples were explored by characterization, and nonlinear optical (NLO) enhancement of nanocomposites (NCs) was fully studied. Nanoparticles and NCs were tested at 532 nm by a Z-scan technique. With γMnS attached in G layers, NLO susceptibility of graphene-γMnS was greatly improved under single-pulse laser irradiation compared with G and γMnS. The nonlinearity enhanced was attributed to local field effect and charge transfer between γMnS and graphene layers. And NLO property enhancement was restricted by non-radiative defects in graphene-γMnS. Exploring the mechanism of nonlinearity enhancement was significant for fabrication of NLO devices. However, the optical nonlinearity decreased first and then increased with further increased addition of GO, because the dispersion of γMnS attached on graphene surface might make density of sp² fragment and defects changed. Graphene-γMnS exhibited excellent and tunable NLO performance, illustrating that NCs materials have potential applications in NLO devices.

Incorporation of Carbon Quantum Dots for Improvement of Supercapacitor Performance of Nickel Sulfide

A facile hydrothermal method is adopted for the synthesis of hierarchical flowerlike nickel sulfide nanostructure materials and their composite with carbon quantum dot (NiS/C-dot) composite. The composite material exhibited good performance for electrochemical energy-storage devices as supercapacitor with a specific capacity of 880 F g-1 at a current density of 2 A g-1. The material remained stable up to the tested 2000 charge-discharge cycles. Carbon quantum dots of size 1.3 nm were synthesized from natural sources and the favorable electronic and surface property of C-dots were utilized for improvement of the supercapacitor performance of NiS. The results from Tafel analysis, double-layer capacitance, and the impedance measurement reveal that the incorporation of C-dots inside the NiS matrix has improved the charge-transfer process, which is mainly responsible for the enhancement of the supercapacitive property of the composite materials.

Hydrothermal synthesis and pseudocapacitive properties of morphology-tuned nickel sulfide (NiS) nanostructures

Metal sulfides have attracted considerable scrutiny compared to metal oxides owing to their distinguished electrochemical properties and various applications, such as solar cells and supercapacitors.

Free-standing Ni3(VO4)2 nanosheet arrays on aminated r-GO sheets for supercapacitor applications

Ni₃(VO₄)₂ nanosheet arrays have been grown on r-GO sheets to tackle the π–π stacking of r-GO sheets in order to improve the electrochemical supercapacitor properties.

Novel Quaternary Chalcogenide/Reduced Graphene Oxide-Based Asymmetric Supercapacitor with High Energy Density

In this work we have synthesized quaternary chalcogenide Cu₂NiSnS₄ (QC) nanoparticles grown in situ on 2D reduced graphene oxide (rGO) for application as anode material of solid-state asymmetric supercapacitors (ASCs). Thorough characterization of the synthesized composite validates the proper phase, stoichiometry, and morphology. Detailed electrochemical study of the electrode materials and ASCs has been performed. The as-fabricated device delivers an exceptionally high areal capacitance (655.1 mF cm^-2), which is much superior to that of commercial micro-supercapacitors. Furthermore, a remarkable volumetric capacitance of 16.38 F cm^-3 is obtained at a current density of 5 mA cm^-2 combined with a very high energy density of 5.68 mW h cm^-3, which is comparable to that of commercially available lithium thin film batteries. The device retains 89.2% of the initial capacitance after running for 2000 cycles, suggesting its long-term capability. Consequently, the enhanced areal and volumetric capacitances combined with decent cycle stability and impressive energy density endow the uniquely decorated QC/rGO composite material as a promising candidate in the arena of energy storage devices. Moreover, Cu₂NiSnS₄ being a narrow band gap photovoltaic material, this work offers a novel protocol for the development of self-charging supercapacitors in the days to come.

NiCo2 S4 Materials for Supercapacitor Applications

Cobalt-nickel sulfide (NiCo₂ S₄ ) shows extensive potential for innovative photoelectronic and energetic materials owing to distinctive physical and chemical properties. In this review, representative strategies for the fabrication and application of NiCo₂ S₄ and composite nanostructures are outlined for supercapacitors, with the aim of promoting the development of NiCo₂ S₄ and their composites in the supercapacitor field through an analysis and comparison of diverse nanostructures. A brief introduction into the structures, properties, and morphologies are presented. Further prospects and promising developments of the materials in the supercapacitor field are also proposed.

A facile one-step route to synthesize the three-layer nanostructure of CuS/RGO/Ni3S2 and its high electrochemical performance

A three-layer nanostructure of CuS/RGO/Ni₃S₂ composite was in situ grown on nickel foam through a one-step hydrothermal-assisted process. This special architecture exhibited good supercapacitor electrochemical performance.

One-step hydrothermal synthesis of 3D petal-like Co9S8/RGO/Ni3S2 composite on nickel foam for high-performance supercapacitors

Co9S8, Ni3S2, and reduced graphene oxide (RGO) were combined to construct a graphene composite with two mixed metal sulfide components. Co9S8/RGO/Ni3S2 composite films were hydrothermal-assisted synthesized on nickel foam (NF) by using a modified "active metal substrate" route in which nickel foam acted as both a substrate and Ni source for composite films. It is found that the Co9S8/RGO/Ni3S2/NF electrode exhibits superior capacitive performance with high capability (13.53 F cm(-2) at 20 mA cm(-2), i.e., 2611.9 F g(-1) at 3.9 A g(-1)), excellent rate capability, and enhanced electrochemical stability, with 91.7% retention after 1000 continuous charge-discharge cycles even at a high current density of 80 mA cm(-2).

Facile synthesis of nickel–cobalt sulfide/reduced graphene oxide hybrid with enhanced capacitive performance

A facile one-pot refluxing method was developed to prepare nickel–cobalt sulfide/reduced graphene oxide (RGO) hybrids. The as-synthesized NiCo₂S₄/RGO hybrids as electrode materials for supercapacitors exhibit excellent electrochemical performance.

An assembled-nanosheets discus-like Ni(OH)2 hierarchical structure as a high performance electrode material for supercapacitors

An assembled-nanosheets discus-like Ni(OH)₂ hierarchical architecture with excellent capacitive performance was prepared using a surfactant-free solvothermal method.

Preparation of chestnut-like porous NiO nanospheres as electrodes for supercapacitors

Nanospheres with chestnut-like structure have been prepared and show good electrochemical capacitance and cycling performance.

Vertically oriented Ni3S2/RGO/Ni3S2 nanosheets on Ni foam for superior supercapacitors

A unique sandwich structure of Ni₃S₂/RGO/Ni₃S₂ was designed on nickel foam by a one-step hydrothermal process.