A Mesoporous High-Performance Supercapacitor Electrode Based on Polypyrrole Wrapped Iron Oxide Decorated Nanostructured Cobalt Vanadium Oxide Hydrate with Enhanced Electrochemical Capacitance

AM, Beknalkar SA, Dhas SD, Shin DK. Ni3V2O8 Marigold Structures with rGO Coating for Enhanced Supercapacitor Performance

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.

Synthesis of a Co3V2O8/CNx hybrid nanocomposite as an efficient electrode material for supercapacitors

Cobalt vanadium oxide/carbon nitride composite (Co₃V₂O₈/CN_x) was synthesized by solvothermal method. This Co₃V₂O₈/CN_x composite was applied for asymmetric supercapacitor application.

A polypyrrole-adorned, self-supported, pseudocapacitive zinc vanadium oxide nanoflower and nitrogen-doped reduced graphene oxide-based asymmetric supercapacitor device for power density applications

Herein, a distinctive approach has been implemented for exploiting a typical battery material zinc vanadium oxide (ZV) as a supercapacitor electrode material.

Synthesis, characterization and biocompatibility of polypyrrole/Cu(II) metal-organic framework nanocomposites

The main objective of composite science is to fabricate new materials with desired properties such as high chemical, mechanical, and/or biological performances. In this research, new conductive nanocomposites of copper metal-organic frameworks (Cu-MOF) and polypyrrole (PPy) were fabricated with the aim of exploiting the electrical conductivity of polypyrrole and the porosity of MOFs in the final products. The prepared compounds (PPy/x%Cu-MOF, x = 20, 50, and 80) were investigated by FTIR, PXRD, SEM, TEM, DLS, BET, EDS mapping, cyclic voltammetry (CV), and zeta potential (ξ) measurements. Spherical morphology was confirmed by SEM and TEM analysis. The PPy/80%Cu-MOF nanocomposite showed the highest ξ potential (-40 mV), demonstrating the stability of dispersed particles. The CV results revealed that the nanocomposites have higher capacitance in comparison to the pure materials. In vitro degradation of the as-prepared compounds in simulated body fluid (SBF) was studied by EIS (electrochemical impedance spectroscopy) and Tafel polarization tests. Furthermore, in vitro biocompatibility of the PPy/x%Cu-MOF composite was evaluated on a group of cells including 3T3 fibroblasts, MCF-7 breast cancer cells, J774.A1 macrophages and red blood cells (RBCs). Viability of 3T3 fibroblasts, MCF-7, and J774.A1 cells, by Methylthiazolyldiphenyl-tetrazolium bromide (MTT) method, was dependent on Cu-MOF percent and amount of composites. Hemolytic assay for RBCs exposed to different amounts of the PPy/x%Cu-MOF composites showed hematological toxicity less than 5% in most concentrations. In addition, to investigate pro-inflammatory activity, J774.A1 macrophages were exposed to non-toxic concentrations of the PPy/x%Cu-MOF and no significant change in the expression of two inflammatory genes COX-2 and iNOS was observed. Injection of the PPy/x%Cu-MOF (5 mg kg^-1) into bloodstream of mice did not increase liver damage marker enzymes alanine transaminase (ALT) and aspartate transaminase (AST) level in serum 1 week post injection. Moreover, we observed slight but not significant increase in serum copper level in mice 1 week after injection. According to the results, the PPy/x%Cu-MOF nanocomposites exhibited a good in vitro and in vivo biocompatibility without inducing pro-inflammatory responses in macrophages and show promising potential for different biomedical applications such as biosensors and drug delivery. The release of curcumin from curcumin-loaded PPy/x%Cu-MOF nanocomposites was detectable in plasma of mice 4 days after administration.

Fe2P4O12–carbon composite as a highly stable electrode material for electrochemical capacitors

A carbon–iron cyclotetraphosphate composite derived from the pyrolysis of a ferric phytate gel is demonstrated as a high-performance and highly durable capacitive material.

Lithium ferrite (α-LiFe5O8) nanorod based battery-type asymmetric supercapacitor with NiO nanoflakes as the counter electrode

The fabricated battery-type NiO//α-LiFe₅O₈ cell could deliver a specific energy of 30 W h Kg⁻¹ at a specific power of 621 W kg⁻¹ with 90.5% capacity retention at the end of 5000 GCD cycles.

FeO x -Based Materials for Electrochemical Energy Storage

Iron oxides (FeO x ), such as Fe2O3 and Fe3O4 materials, have attracted much attention because of their rich abundance, low cost, and environmental friendliness. However, FeO x , which is similar to most transition metal oxides, possesses a poor rate capability and cycling life. Thus, FeO x -based materials consisting of FeO x , carbon, and metal-based materials have been widely explored. This article mainly discusses FeO x -based materials (Fe2O3 and Fe3O4) for electrochemical energy storage applications, including supercapacitors and rechargeable batteries (e.g., lithium-ion batteries and sodium-ion batteries). Furthermore, future perspectives and challenges of FeO x -based materials for electrochemical energy storage are briefly discussed.