The influence of crystal structures on the performance of CoMoO4 battery-type supercapacitor electrodes

CoMoO4 is a promising battery-type supercapacitor electrode material that can offer relatively high storage capacity and cycle stability. In this work, we investigate the role of the crystalline phase of CoMoO4 in determining these performance parameters. The hydrate phase of CoMoO4 was synthesized on a nickel foam substrate via hydrothermal reaction with subsequent annealing under an inert atmosphere leading to the formation of the β-phase CoMoO4. Similar nanoplate morphologies were observed in all of the samples. The hydrate-phase CoMoO4 demonstrates larger specific capacity than the annealed β-phase CoMoO4. Besides, the samples synthesized at lower temperatures have better rate capability than the sample annealed at higher temperatures. However, the hydrate phase had worse long-term stability compared to the β-phase samples.

Gamma-induced interconnected networks in microporous activated carbons from palm petiole under NaNO3 oxidizing environment towards high-performance electric double layer capacitors (EDLCs)

Activated carbons (ACs) were developed from palm petiole via a new eco-friendly method composed of highly diluted H2SO4 hydrothermal carbonization and low-concentration KOH-activating pyrolysis followed by gamma-induced surface modification under NaNO3 oxidizing environment. The prepared graphitic carbons were subsequently used as an active material for supercapacitor electrodes. The physiochemical properties of the ACs were characterized using field emission scanning electron microscope-energy dispersive X-ray spectroscopy, N2 adsorption/desorption isotherms with Brunauer-Emmett-Teller surface area analysis, Fourier transform infrared spectroscopy, X-ray diffraction and Raman spectroscopy. The electrochemical performance of the fabricated electrodes was investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Even treated with extremely low H2SO4 concentration and small KOH:hydrochar ratio, the maximum SBET of 1365 m2 g-1 for an AC was obtained after gamma irradiation. This was attributed to radiation-induced interconnected network formation generating micropores within the material structure. The supercapacitor electrodes exhibited electric double-layer capacitance giving the highest specific capacitance of 309 F g-1 as well as excellent cycle stability within 10,000 cycles. The promising results strongly ensure high possibility of the eco-friendly method application in supercapacitor material production.

High-performance freestanding supercapacitor electrode based on polypyrrole coated nickel cobalt sulfide nanostructures

In the present work, we report the successful fabrication of dandelion-like Nickel-Cobalt Sulfide@Polypyrrole microspheres through the hydrothermal method and its possible application as a binder-free electrode in supercapacitors. This electrode exhibited low charge transfer resistance with a remarkable specific capacitance of 2554.9 F g^-1 at 2.54 A g^-1, in addition to considerable cycle life stability. Also, an asymmetric device was prepared using NiCo₂S₄@PPy/NF as positive and rGO/NF as negative electrodes. This asymmetric supercapacitor exhibited a specific capacitance of 98.9 F g^-1 at 1.84 A g^-1 and delivered an energy density of 35.17 Wh kg^-1 at a power density of 1472 W kg^-1. Such a remarkable performance can be originated from the synergy effect of NiCo₂S₄ and PPy and the direct deposition of the composite on the current collector. Our findings suggest the dandelion-like NiCo₂S₄@PPy as a promising material for making high-performance supercapacitors.

Electrochemical Performance of 2D-Hierarchical Sheet-Like ZnCo2O4 Microstructures for Supercapacitor Applications

With the rapid improvement of the global economy, the role of energy has become even more vital in the 21st century. In this regard, energy storage/conversion devices have become a major, worldwide research focus. In response to this, we have prepared two-dimensional (2D)-hierarchical sheet-like ZnCo2O4 microstructures for supercapacitor applications using a simple hydrothermal method. The 2D-hierarchical sheet-like morphologies with large surface area and smaller thickness enhanced the contact area of active material with the electrolyte, which increased the utilization rate. We investigated the electrochemical performance of sheet-like ZnCo2O4 microstructures while using Cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), and Electrochemical impedance spectroscopy (EIS) analysis. The electrochemical results demonstrated that the ZnCo2O4 electrode possesses 16.13 mF cm−2 of areal capacitance at 10 µA cm−2 of current density and outstanding cycling performance (170% of capacitance is retained after 1000 cycles at 500 µA cm−2). The high areal capacitance and outstanding cycling performance due to the unique sheet-like morphology of the ZnCo2O4 electrode makes it an excellent candidate for supercapacitor applications.

Bubble-assisted fabrication of hollow CoMoO4 spheres for energy storage

Herein, gas bubbles generated in situ from precursors assist the rapid construction of hollow sycamore fruit-like CoMoO4 spheres (HSCSs). This bubble-assisted fabrication strategy is easy to operate, ultra-fast, low cost and post-treatment-free, showing great potential for the large-scale production of HSCSs. The growth mechanism of HSCSs is discussed to reveal the evolution process, which may be generalized to the construction of a series of hollow ternary Mo-based oxides. The obtained HSCSs exhibit a superior specific capacitance and outstanding cyclic stability when applied in supercapacitors.

Hydrothermal Synthesized of CoMoO4 Microspheres as Excellent Electrode Material for Supercapacitor

The single-phase CoMoO₄ was prepared via a facile hydrothermal method coupled with calcination treatment at 400 °C. The structures, morphologies, and electrochemical properties of samples with different hydrothermal reaction times were investigated. The microsphere structure, which consisted of nanoflakes, was observed in samples. The specific capacitances at 1 A g^-1 are 151, 182, 243, 384, and 186 F g^-1 for samples with the hydrothermal times of 1, 4, 8, 12, and 24 h, respectively. In addition, the sample with the hydrothermal time of 12 h shows a good rate capability, and there is 45% retention of initial capacitance when the current density increases from 1 to 8 A g^-1. The high retain capacitances of samples show the fine long-cycle stability after 1000 charge-discharge cycles at current density of 8 A g^-1. The results indicate that CoMoO₄ samples could be a choice of excellent electrode materials for supercapacitor.

Synthesis of Li2Ni2(MoO4)3 as a high-performance positive electrode for asymmetric supercapacitors

A NASICON-type compound, Li₂Ni₂(MoO₄)₃ was successfully synthesized via a combustion method to be used as positive electrode for asymmetric supercapacitors with good performance.

Facile synthesis of a MnFe2O4/rGO nanocomposite for an ultra-stable symmetric supercapacitor

A symmetric supercapacitor based on a MnFe₂O₄/rGO nanocomposite prepared from expanded graphite.

Mn0.5Co2.5O4 nanofibers sandwiched in graphene sheets for efficient supercapacitor electrode materials

With unique sandwich-like structures, rich active sites, and boosted electrical conductivity, the Mn_0.5Co_2.5O₄@G composite demonstrates superior electrochemical performances for supercapacitors.

Binder-free electrodes of NiMoO4/graphene oxide nanosheets: synthesis, characterization and supercapacitive behavior

In the present work we report a facile and efficient hydrothermal method to fabricate a nanocomposite of NiMoO₄ and graphene nanosheets (NiMoO₄/GNS) on a nickel foam (NF) substrate.