Three-dimensional ordered macroporous NiFe2O4 coated carbon yarn for knittable fibriform supercapacitor

Carbon quantum dots modified and Y3+ doped Ni3(NO3)2(OH)4 nanospheres with excellent battery-like supercapacitor performance

Supercapacitor is an important energy storage device widely used in the automobile industry, military production, and communication equipment because of its fast charge-discharge rate, and high power density. Herein, carbon quantum dots modified and Y3+ doped Ni3(NO3)2(OH)4 (NiY@CQDs) nanospheres are prepared by a solvothermal method and used as an electrode material. The electrochemical properties of NiY@CQDs were measured in a three-electrode system. An asymmetric supercapacitor (ASC) cell was assembled with activated carbon (AC) as the anode and NiY@CQDs as the cathode. The electrochemical properties of the ASC device were measured in a two-electrode system. Experimental results show the shape of NiY@CQDs is petal-shaped and the introducing carbon quantum dots and doping Y3+ significantly increases the specific surface area, conductivity, and specific capacitance of Ni3(NO3)2(OH)4. The mass-specific capacitance of NiY@CQDs reaches up to 2944 F g-1 at a current density of 1 A g-1. The asymmetric supercapacitor of NiY@CQDs//AC has a high energy density of 138.65 Wh kg-1 at a power density of 1500 W kg-1, displaying a wide range of application prospects in the energy storage area.

Exploring the redox characteristics of porous ZnCoS@rGO grown on nickel foam as a high-performance electrode for energy storage applications

A supercapattery is a device that combines the properties of batteries and supercapacitors, such as power density and energy density. A binary composite (zinc cobalt sulfide) and rGO are synthesized using a simple hydrothermal method and modified Hummers' method. A notable specific capacity (C_s) of 1254 C g^-1 is obtained in the ZnCoS@rGO case, which is higher than individual C_s of ZnS (975 C g^-1) and CoS (400 C g^-1). For the asymmetric (ASC) device (ZnCoS@rGO//PANI@AC), the PANI-doped activated carbon and ZnCoS@rGO are used as the cathode and anode respectively. A high C_m of 141 C g^-1 is achieved at 1.4 A g^-1. The ASC is exhibited an extraordinary energy density of 45 W h kg^-1 with a power density 5000 W kg^-1 at 1.4 A g^-1. To check the stability of the device, the ASC device is measured for 2000 charging/discharging cycles. The device showed improved coulombic efficiency of 94%. These findings confirmed that the two-dimensional materials provide the opportunities to design battery and supercapacitor hybrid devices.

Conductive Metal-Organic Frameworks for Supercapacitors

As a class of porous materials with crystal lattices, metal-organic frameworks (MOFs), featuring outstanding specific surface area, tunable functionality, and versatile structures, have attracted huge attention in the past two decades. Since the first conductive MOF is successfully synthesized in 2009, considerable progress has been achieved for the development of conductive MOFs, allowing their use in diverse applications for electrochemical energy storage. Among those applications, supercapacitors have received great interest because of their high power density, fast charging ability, and excellent cycling stability. Here, the efforts hitherto devoted to the synthesis and design of conductive MOFs and their auspicious capacitive performance are summarized. Using conductive MOFs as a unique platform medium, the electronic and molecular aspects of the energy storage mechanism in supercapacitors with MOF electrodes are discussed, highlighting the advantages and limitations to inspire new ideas for the development of conductive MOFs for supercapacitors.

Formation of graphene-wrapped multi-shelled NiGa2O4 hollow spheres and graphene-wrapped yolk-shell NiFe2O4 hollow spheres derived from metal-organic frameworks for high-performance hybrid supercapacitors

To construct a supercapacitor (SC) with considerable performance, synthesis of an electrode material with a highly porous structure is necessary. Herein, an efficient metal-organic framework (MOF)-derived procedure is offered to construct a graphene wrapped multi-shelled NiGa2O4 hollow sphere (GW-MSNGOHS) positive electrode material and a graphene-wrapped yolk-shell NiFe2O4 hollow sphere (GW-YS-NFOHS) negative electrode material with a highly porous nature in SCs. The GW-MSNGOHS and GW-YS-NFOHS electrodes exhibit excellent capacities (∼411.25 mA h g-1 and 254.25 mA h g-1, respectively, at 1 A g-1), reasonable rate performances (75.85%, and 62.7%, respectively), and outstanding cyclability (98.9% and 90.9%, respectively). Benefiting from the reasonably engineered negative and positive electrodes, the fabricated asymmetric device (GW-MSNGOHS//GW-YS-NFOHS) can show an excellent energy density (ED) of 118.97 W h kg-1 at a power density (PD) of 1702 W kg-1, an exceptional robustness of 92.1%, and an excellent capacity (Cs) of 140.2 mA g-1.

NiFe2O4@ nitrogen-doped carbon hollow spheres with highly efficient and recyclable adsorption of tetracycline

Antibiotics can affect ecosystems and threaten human health; therefore, methods for removing antibiotics have become a popular subject in environmental management and for the protection of human health. Adsorption is considered an effective approach for the removal of antibiotics from water. In this study, NiFe₂O₄@nitrogen-doped carbon hollow spheres (NiFe₂O₄/NCHS) were synthesized via a facile hydrothermal method followed by calcination using NCHS as a hard template. The nanocomposite exhibited high adsorption activity and good recyclability. The nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen adsorption–desorption to study its micromorphology, structure, and chemical composition/states. In addition, the factors affecting the adsorption process were systematically investigated, including tetracycline (TC) concentration, solution pH, ionic strength, and temperature. The maximum adsorption capacity for TC was calculated to be 271.739 mg g⁻¹ based on the Langmuir adsorption model, which was higher than various other materials. This study provides an effective method for constructing the NiFe₂O₄/NHCS core–shell structure, which can be applied for the removal of TC from water.

Antibiotics can affect ecosystems and threaten human health; therefore, methods for removing antibiotics have become a popular subject in environmental management and for the protection of human health.