Meso-macroporous Co3O4 electrode prepared by polystyrene spheres and carbowax templates for supercapacitors

Recent progress in metal oxide-based electrode materials for safe and sustainable variants of supercapacitors

A significant amount of energy can be produced using renewable energy sources; however, storing massive amounts of energy poses a substantial obstacle to energy production. Economic crisis has led to rapid developments in electrochemical (EC) energy storage devices (EESDs), especially rechargeable batteries, fuel cells, and supercapacitors (SCs), which are effective for energy storage systems. Researchers have lately suggested that among the various EESDs, the SC is an effective alternate for energy storage due to the presence of the following characteristics: SCs offer high-power density (PD), improvable energy density (ED), fast charging/discharging, and good cyclic stability. This review highlighted and analyzed the concepts of supercapacitors and types of supercapacitors on the basis of electrode materials, highlighted the several feasible synthesis processes for preparation of metal oxide (MO) nanoparticles, and discussed the morphological effects of MOs on the electrochemical performance of the devices. In this review, we primarily focus on pseudo-capacitors for SCs, which mainly contain MOs and their composite materials, and also highlight their future possibilities as a useful application of MO-based materials in supercapacitors. The novelty of MO's electrode materials is primarily due to the presence of synergistic effects in the hybrid materials, rich redox activity, excellent conductivity, and chemical stability, making them excellent for SC applications.

Fabrication of High-Performance Asymmetric Supercapacitor Consists of Nickel Oxide and Activated Carbon (NiO//AC)

Exploring faster, safer, and more efficient energy storage devices will motivate scientists to develop novel energy storage products with high performance. Herein, we report porous NiO nanoparticles have been prepared by a simple hydrothermal method with CTAB and laboratory tissue paper as a template followed by calcination at three different temperatures (300, 500, and 700 °C). The electrochemical characteristics of the prepared materials were examined in a three-electrode cell configuration using aqueous potassium hydroxide (2.0 M KOH) electrolyte. The NiO-300 electrode displayed the supreme capacitance of 568.7 F g−1 at 0.5 A g−1. The fascinating NiO morphology demonstrates a crucial part in offering simple ion transport, shortening electron, and ion passage channels and rich energetic spots for electrochemical reactions. Finally, the asymmetric supercapacitor (ASC), NiO//AC was constructed using positive and negative electrode materials of NiO-300 and activated carbon (AC), respectively. The assembled ASC displayed excellent supercapacitive performance with a high specific energy (52.4 Wh kg−1), specific power (800 W kg−1), and remarkable cycle life. After quick charging (25 s), such supercapacitors in the series will illuminate the light emitting diode for an extended time, suggesting improvements in energy storage, scalable integrated applications, and ensuring business efficacy. This work will lead to a new generation of high-performance ASCs to portable electronic displays and electric automobiles.

Removal of Phenol from Steel Plant Wastewater in Three Dimensional Electrochemical (TDE) Process using CoFe2O4@AC/H2O2

This study investigated the removal of phenol from steel industry wastewater by three dimensional electrochemical (TDE) process using CoFe2O4 nanobiocomposite based activated carbon in the presence of H2O2 (EC-CoFe2O4@AC-H2O2). In this study, CoFe2O4 nanobiocomposite-foundation activated carbon (CoFe2O4@AC) was used as microelectrode, adsorbent, and activator for peroxide hydrogen. The removal efficiency of phenol and COD was investigated through the parameters of pH, contact time, CoFe2O4@AC dosage, current density, and H2O2 concentration. The highest removal rates of phenol and COD were >99% and 98%, respectively. Also, steel plant wastewater under the optimal conditions of pH = 6.5, current density = 15 mA cm−2, contact time = 25 min, H2O2 concentration of 1.0 mM, and CoFe2O4@AC dose = 0.3 g L−1. Kinetic analysis revealed that the adsorption experimental data was best fitted by the pseudo-first-order model.

Highly active 3-dimensional cobalt oxide nanostructures on the flexible carbon substrates for enzymeless glucose sensing

3-Dimensional cobalt oxide nanostructures on the flexible carbon substrates for enzymeless glucose sensing.

Assembly of NiO/Ni(OH)2/PEDOT Nanocomposites on Contra Wires for Fiber-Shaped Flexible Asymmetric Supercapacitors

Fiber-shaped solid-state supercapacitors have aroused much interest in the fields of portable devices because of their attractive features such as high flexibility and safety, tiny volume, and high power density. In this work, NiO/Ni(OH)2 nanoflowers encapsulated in three-dimensional interconnected poly(3,4-ethylenedioxythiophene) (PEDOT) have been fabricated on contra wires through a mild electrochemical route. The as-formed hybrid electrode made of NiO/Ni(OH)2/PEDOT delivered a high specific capacitance of 404.1 mF cm(-2) (or 80.8 F cm(-3)) at a current density of 4 mA cm(-2) and a long cycle life with 82.2% capacitance retention after 1000 cycles. Furthermore, a fiber-shaped flexible all-solid-state asymmetric supercapacitor based on the resulting hybrid electrode was assembled. The energy density of 0.011 mWh cm(-2) at a power density of 0.33 mW cm(-2) was achieved under an operating voltage window of 1.45 V. This work provides an effective strategy to fabricate high-performance electrodes for fiber-shaped flexible asymmetric supercapacitors through a facile and low-cost route.

Amorphous Ni-Co Binary Oxide with Hierarchical Porous Structure for Electrochemical Capacitors

A simple and outstanding approach is provided to fabricate amorphous structure Ni-Co binary oxide as supercapacitors electrode materials. We can easily obtain porous Ni-Co oxides composite materials via chemical bath deposition and subsequent calcination without any template or complicate operation procedures. The amorphous porous Ni-Co binary oxide exhibits brilliant electrochemical performance: first, the peculiar porous structure can effectively transport electrolytes and shorten the ion diffusion path; second, binary composition and amorphous character introduce more surface defects for redox reactions. It shows a high specific capacitance up to 1607 F g(-1) and can be cycled for 2000 cycles with 91% capacitance retention. In addition, the asymmetric supercapacitor delivers superior energy density of 28 W h kg(-1), and the maximum power density of 3064 W kg(-1) with a high energy density of 10 W h kg(-1).

Hollow Fluffy Co3O4 Cages as Efficient Electroactive Materials for Supercapacitors and Oxygen Evolution Reaction

Nano-/micrometer multiscale hierarchical structures not only provide large surface areas for surface redox reactions but also ensure efficient charge conductivity, which is of benefit for utilization in areas of electrochemical energy conversion and storage. Herein, hollow fluffy cages (HFC) of Co3O4, constructed of ultrathin nanosheets, were synthesized by the formation of Co(OH)2 hollow cages and subsequent calcination at 250 °C. The large surface area (245.5 m2 g(-1)) of HFC Co3O4 annealed at 250 °C ensures the efficient interaction between electrolytes and electroactive components and provides more active sites for the surface redox reactions. The hierarchical structures minimize amount of the grain boundaries and facilitate the charge transfer process. Thin thickness of nanosheets (2-3 nm) ensures the highly active sites for the surface redox reactions. As a consequence, HFC Co3O4 as the supercapacitor electrode exhibits a superior rate capability, shows an excellent cycliability of 10,000 cycles at 10 A g(-1), and delivers large specific capacitances of 948.9 and 536.8 F g(-1) at 1 and 40 A g(-1), respectively. Catalytic studies of HFC Co3O4 for oxygen evolution reaction display a much higher turnover frequency of 1.67×10(-2) s(-1) in pH 14.0 KOH electrolyte at 400 mV overpotential and a lower Tafel slope of 70 mV dec(-1). HFC Co3O4 with the efficient electrochemical activity and good stability can remain a promising candidate for the electrochemical energy conversion and storage.

Preparation and performance of Co3O4–NiO composite electrode material for supercapacitors

A Co₃O₄–NiO composite electrode material in water–ethanol solution was synthesized in large scaleviatwo steps: preparation of the precursor and a calcination process.