Mesoporous Fe–Ni–Co ternary oxide nanoflake arrays on Ni foam for high-performance supercapacitor applications

Green synthesis of flower shape ZnO-GO nanocomposite through optimized discharge parameter and its efficiency in energy storage device

Numerous solution-based methods are used to prepare zinc oxide (ZnO) and graphene oxide (GO) nanocomposite (ZnO-GO NCs) such as sol-gel, hydrothermal, and precipitation. These methods require lots of reagents and involve many stages. In this study, a novel one-step solution-based discharge method is used to prepare ZnO-GO NCs through an electrochemical discharge process (ECDP) without the use of any catalyst or toxic chemical reagent. This study focused on analyzing the effects of input parameters on the production rate of ZnO-GO NCs. The experiment was performed by using Taguchi L9 orthogonal array. Materials removal rate (MRR) is considered as output response. The results reveal that voltage is the most significant factor, followed by temperature and duty cycle for obtaining higher MRR. The optimum parameters obtained from the Minitab software for higher MRR are 40 V, 30%, and 45 °C. Further, the morphology of the nanoparticles (NCs) produced at optimum parameters is analyzed which shows flower shape NCs with multilayer graphene oxide, confirmed by the FESEM and TEM images. The XRD peak at 11.27° and Raman spectroscopy peak of G and D bands reveal GO formation. The prepared ZnO-GO NCs tested as supercapacitor activity in the KOH solution. At the optimum parameter, the specific capacitance is observed to be 523.4 F/g at 2A/g current density. The NCs electrode shows good cyclic stability, with 86% retention of specific capacitance after 5000 cycles. This study shows a promising future of converting the e-waste product into valuable nanomaterials such as GO and ZnO from used dry cell batteries.

Plasma-Engineered N-CoOx Nanowire Array as a Bifunctional Electrode for Supercapacitor and Electrocatalysis

Surface engineering has achieved great success in enhancing the electrochemical activity of Co₃O₄. However, the previously reported methods always involve high-temperature calcination processes which are prone to induce agglomeration of the nanostructure, leading to the attenuation of performance. In this work, Co₃O₄ nanowires were successfully modified by a low-temperature NH₃/Ar plasma treatment, which simultaneously generated a porous structure and efficient nitrogen doping with no agglomeration. The modified N-CoO_x electrode exhibited remarkable performance due to the synergistic effect of the porous structure and nitrogen doping, which provided additional active sites for faradic transitions and improved charge transfer characteristics. The electrode achieved excellent supercapacitive performance with a maximum specific capacitance of 2862 mF/cm² and superior cycling retention. Furthermore, the assembled asymmetric supercapacitor (N-CoO_x//AC) device exhibited an extended potential window of 1.5 V, a maximum specific energy of 80.5 Wh/kg, and a maximum specific power of 25.4 kW/kg with 91% capacity retention after 5000 charge-discharge cycles. Moreover, boosted hydrogen evolution reaction performance was also confirmed by the low overpotential (126 mV) and long-term stability. This work enlightens prospective research on the plasma-enhanced surface engineering strategies.

Facile construction of core-shell Carbon@CoNiO2 derived from yeast for broadband and high-efficiency microwave absorption

Manufacturing dielectric/magnetic composites with hierarchical structure is regard as a promising strategy for the progress of high-performance microwave absorption (MA) materials. In this paper, the nano-grass structured CoNiO₂ magnetic shell was uniformly anchored on the yeast-derived carbon microspheres by in-situ one-pot synthesis method. Profiting from the unique nano-grass and core-shell structure, capable dielectric/magnetic loss, along with improved impedance matching, the prepared absorber realizes desirable MA performance. The minimum reflection loss (RL_min) reaches up to -44.06 dB at 6.56 GHz. Moreover, the effective absorption bandwidth (EAB, reflection loss (RL) < -10 dB) accomplishes 7.04 GHz under a low filler loading of 20 wt%. This work endeavors a valuable insight for designing innovative core-shell structured materials with high-efficiency MA and broad bandwidth.

Development of Binder Free Interconnected 3D Flower of NiZn2O4 as an Advanced Electrode Materials for Supercapacitor Applications

The design and development of electrode materials for energy-storage applications is an area of prime focus around the globe because of the shortage of natural resources. In this study, we developed a method for preparing a novel three-dimensional binder-free pseudocapacitive NiZn2O4 active material, which was grown directly over nickel foam (NiZn2O4@3D-NF), using a simple one-step hydrothermal process. The material was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques were employed to evaluate the pseudocapacitive performance of the NiZn2O4 active material in a three-electrode assembly cell. The prepared NiZn2O4@3D-NF electrode exhibited an excellent specific capacitance, of 1706.25 F/g, compared to that of the NiO@3D-NF (1050 F/g) electrode because it has the bimetallic characteristics of both zinc and nickel. The NiZn2O4@3D-NF electrode showed better cyclic stability (87.5% retention) compared to the NiO@3D-NF electrode (80% retention) after 5000 cycles at a fixed current density, which also supports the durability of the NiZn2O4@3D-NF electrode. The characteristics of NiZn2O4@3D-NF include corrosion resistance, high conductivity, an abundance of active sites for electrochemical reaction, a high surface area, and synergism between the bimetallic oxides, which make it a suitable candidate for potential application in the field of energy storage.

3D Hierarchically Mesoporous Zinc-Nickel-Cobalt Ternary Oxide (Zn0.6Ni0.8Co1.6O4) Nanowires for High-Performance Asymmetric Supercapacitors

Increased efforts have been devoted recently to develop high-energy-density supercapacitors (SC) without renouncing their power efficiency. Herein, a hierarchically mesoporous nanostructure of zinc-nickel-cobalt oxide (ZNCO) nanowires (NWs) is constructed by hierarchical aggregation of ZNCO nanoparticles. It is worth noting that cobalt and nickel rich lattice imparts higher charge storage capability by enhanced reversible Faradaic reaction while zinc provides structural stability and higher conductivity. Moreover, particulate nature of ZNCO NWs allows deep diffusion of electrolyte thus enabling reversible charge storage under higher current densities. The as-prepared ZNCO NWs exhibited excellent specific capacitance of 2082.21 F g⁻¹ at the current density of 1 A g⁻¹ with high stability up to 5,000 charge-discharge cycles. Further, the asymmetric SC device was assembled using ZNCO NWs (ZNCO NWs//MWCNTs) which exhibited high energy density of 37.89 Wh kg⁻¹ and excellent capacitance retention up to 88.5% over 1,000 cycles. This work presents ways to construct multi-component high-energy-density materials for next-generation energy storage devices.

Transition metal sulfide-laminated copper wire for flexible hybrid supercapacitor

The CV profiles of transition metal sulphide electrodes on a Cu-wire (a), and (b) capacitive (light to dark: blue and red) and diffusion-controlled (dark: blue and red) contributions of the hybrid Cu@CoS/NiCo₂S₄ and Cu@ZnCo₂S₄ electrodes.

Ni-Co Selenide Nanosheet/3D Graphene/Nickel Foam Binder-Free Electrode for High-Performance Supercapacitor

Transition-metal selenide electrodes have recently attracted increasing interest in supercapacitors resulting from their superior electrochemical performance, lower-cost, and environmental friendliness. Herein, we report a novel bimetallic Ni-Co selenide nanosheet/three-dimensional (3D) graphene/nickel foam binder-free electrode (NiCo_2.1Se_3.3 NSs/3D G/NF) prepared via chemical vapor deposition followed by a simple two-step hydrothermal process in this paper. The NiCo_2.1Se_3.3 NSs array vertically on 3D G/NF with a uniform and stable structure without using any chemical binders. This novel electrode is flexible, highly conductive, and exhibits an excellent specific capacitance of ∼742.4 F g^-1 at 1 mA cm^-2. Furthermore, with a 10-fold increase to 10 mA cm^-2, it still retains 471.78 F g^-1 and a high cycling stability of ∼83.8% of the initial retention after 1000 cycles at 10 mA cm^-2, demonstrating that NiCo_2.1Se_3.3 NSs/3D G/NF binder-free electrode has potential for energy storage application in high-performance supercapacitor fields.