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In this work, Ni3V2O8 (NVO) and Ni3V2O8-reduced graphene oxide (NVO-rGO) are synthesized hydrothermally, and their extensive structural, morphological, and electrochemical characterizations follow subsequently. The synthetic materials’ crystalline structure was confirmed by X-ray diffraction (XRD), and its unique marigold-like morphology was observed by field emission scanning electron microscopy (FESEM). The chemical states of the elements were investigated via X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS), Galvanostatic charge–discharge (GCD), and cyclic voltammetry (CV) were used to assess the electrochemical performance. A specific capacitance of 132 F/g, an energy density of 5.04 Wh/kg, and a power density of 187 W/kg were demonstrated by Ni3V2O8-rGO. Key electrochemical characteristics were b = 0.67; a transfer coefficient of 0.52; a standard rate constant of 6.07 × 10−5 cm/S; a diffusion coefficient of 5.27 × 10−8 cm2/S; and a series resistance of 1.65 Ω. By employing Ni3V2O8-rGO and activated carbon, an asymmetric supercapacitor with a specific capacitance of 7.85 F/g, an energy density of 3.52 Wh/kg, and a power density of 225 W/kg was achieved. The series resistance increased from 4.27 Ω to 6.63 Ω during cyclic stability tests, which showed 99% columbic efficiency and 87% energy retention. The potential of Ni3V2O8-rGO as a high-performance electrode material for supercapacitors is highlighted by these findings.

The hydrothermal method has been utilized to synthesize graphitic carbon nitride (g-C3N4) polymers and cobalt oxide composites effectively. The weight percentage of g-C3N4 nanoparticles influenced the electrochemical performance of the Co3O4-g-C3N4 composite. In an aqueous electrolyte, the Co3O4-g-C3N4 composite electrode, produced with 150 mg of g-C3N4 nanoparticles, revealed remarkable electrochemical performance. With an increase in the weight percentage of g-C3N4 nanoparticles, the capacitive contribution of the Co3O4-g-C3N4 composite electrode increased. The Co3O4-g-C3N4-150 mg composite electrode shows a specific capacitance of 198 F/g. The optimized electrode, activated carbon, and polyvinyl alcohol gel with potassium hydroxide were used to develop an asymmetric supercapacitor. At a current density of 5 mA/cm2, the asymmetric supercapacitor demonstrated exceptional energy storage capacity with remarkable energy density and power density. The device retained great capacity over 6k galvanostatic charge–discharge (GCD) cycles, with no rise in series resistance following cyclic stability. The columbic efficiency of the asymmetric supercapacitor was likewise high.

To maximize the use of ZnS low-dimensional nanoparticles as high-performance supercapacitor electrodes, this work describes a simple one-pot synthesis method for producing a cluster of these particles. The ZnS nanoparticles fabricated in this work exhibit a cluster with unique low-dimensional (0D, 1D, and 2D) characteristics. Structural, morphological, and electrochemical investigations are all part of the thorough characterization of the produced materials. An X-ray diffraction pattern of clustered ZnS nanoparticles reflects the phase formation with highly stable cubic blende sphalerite polymorph. The confirmation of nanoparticle cluster formation featuring multiple low-dimensional nanostructures was achieved through field emission scanning electron microscopy (FE-SEM), while the internal structure was assessed using transmission electron microscopy (TEM). Systematically assessing the ZnS nanoparticles’ electrochemical performance reveals their prospective qualities as supercapacitor electrode materials. The electrode assembled with this material on Ni foam demonstrates elevated specific capacitance (areal capacitance) values, reaching 716.8 F.g⁻1 (2150.4 mF.cm−2) at a current density of 3 mA.cm⁻2. Moreover, it reflects 69.1% capacitance retention with a four times increase in current density, i.e., 495.5 F.g−1 (1486.56 mF.cm−2) capacitance was archived at 12 mA.cm−2 with 100% Coulombic efficiency. Furthermore, the electrode exhibits prolonged cycling capability with 77.7% capacitance retention, as evidenced by its charge–discharge measurements sustained over 15,000 cycles at a current density of 25 mA cm⁻2.