Template synthesis and characterization of nanostructured hierarchical mesoporous ribbon-like NiO as high performance electrode material for supercapacitor

Insight into the photocatalytic properties of diatomite@Ni/NiO composite for effective photo-degradation of malachite green dye and photo-reduction of Cr (VI) under visible light

Diatomite frustules decorated by nano Ni/NiO nanoparticles (Diatomite@Ni/NiO) were synthesized as a novel photocatalyst for effective degradation of malachite green cationic dye (M.G) and photocatalytic-reduction of Cr (VI) ions. The composite was characterized by different analytical techniques and revealed enhancing in the surface area (400 m²/g), 5.8 nm as average pore diameter and showed lower band gap energy (1.71 eV) than NiO as single phase. The photocatalytic activity of the composite in the removal of M.G and reduction of Cr (VI) was evaluated under visible light considering the pH, illumination time, catalyst mass, and the pollutants concentrations. The results revealed complete removal of 25 mg/L M.G can be achieved using 20 mg, 30 mg, 40 mg and 50 mg of the after 150 min, 90 min, 60 min, and 30 min, respectively. The complete degradation of 50 mg/L can be obtained after 240 min, 90 min, and 60 min using 20 mg, 40 mg, and 50 mg of the catalyst, respectively. This also was reported for the photocatlytic-reduction of 25 mg/L of Cr(VI) ions as the complete reduction was estimated after 180 min, 60 min and 30 min using 20 mg, 40 mg, and 50 mg, respectively. Also, 50 mg/L of Cr (VI) can be completely reduced after 240 min, 90 min, and 60 min using 20 mg, 40 mg, and 50 mg as catalyst dosage, respectively. The photocatalytic degradation of M.G controlled mainly by the generated electron-hole pairs and the superoxide species while the photocatalytic-reduction of Cr (VI) controlled mainly by the directly excited electrons of Ni/NiO and partially by the formed superoxide radicals. Hence, the synthetic diatomite@Ni/NiO composite can be considered as potential photocatalyst in the degradation of M.G dye and photoreduction of Cr (VI) ions.

Novel mesoporous electrode materials for symmetric, asymmetric and hybrid supercapacitors

Electrochemical capacitors or supercapacitors have achieved great interest in the recent past due to their potential applications ranging from microelectronic devices to hybrid electric vehicles. Supercapacitors can provide high power densities but their inherently low energy density remains a great challenge. The high-performance supercapacitors utilize large electrode surface area for electrochemical double-layer capacitance and/or pseudocapacitance. To enhance the performance of supercapacitors, various strategies have been adopted such as electrode nanostructuring, hybrid electrode designs using nanocomposite electrodes and hybrid supercapacitor (HSC) configurations. Nanoarchitecturing of electrode-active materials is an effective way of enhancing the performance of supercapacitors as it increases the effective electrode surface area for enhanced electrode/electrolyte interaction. In this review, we focus on the recent developments in the novel electrode materials and various hybrid designs used in supercapacitors for obtaining high specific capacitance and energy density. A family of electrode-active materials including carbon nanomaterials, transition metal-oxides, transition metal-nitrides, transition metal-hydroxides, electronically conducting polymers, and their nanocomposites are discussed in detail. The HSC configurations for attaining enhanced supercapacitor performance as well as strategies to integrate with other microelectronic devices/wearable fabrics are also included.

A 3D walking palm-like core-shell CoMoO4@NiCo2S4@nickel foam composite for high-performance supercapacitors

Supercapacitors are one of the most promising renewable-energy storage systems. In this study, a three-dimensional walking palm-like core-shell CoMoO4@NiCo2S4@nickel foam (NF) nanostructure was synthesized using a two-step hydrothermal method for high electrochemical performance. The as-prepared composite exhibited a high areal capacitance of 17.0 F cm-2 (2433 F g-1) at a current density of 5 mA cm-2 in a three-electrode system. The results revealed outstanding cycling stability of 114% after 10 000 charge-discharge cycles. An aqueous asymmetric supercapacitor device assembled with CoMoO4@NiCo2S4@NF and activated carbon (AC)@NF as the positive and negative electrodes, respectively, showed a high capacitance of 4.19 F cm-2 (182 F g-1) and delivered a high energy density of 60.2 W h kg-1 at a power density of 188 W kg-1 and a high power density of 1.5 kW kg-1 at an energy density 29.2 W h kg-1, lighting 22 parallel-connected red light emitting diodes for over 60 s. The synergistic effects of the core-shell CoMoO4@NiCo2S4@NF electrode material highlight the potential of this composite as an effective active material for supercapacitor applications.

Enhanced electrochemical performance of nanoplate nickel cobaltite (NiCo2O4) supercapacitor applications

Well-ordered, unique interconnected nanostructured binary metal oxides with lightweight, free-standing, and highly flexible nickel foam substrate electrodes have attracted tremendous research attention for high performance supercapacitor applications owing to the combination of the improved electrical conductivity and highly efficient electron and ion transport channels. In this study, a unique interconnected nanoplate-like nickel cobaltite (NiCo2O4) nanostructure was synthesized on highly conductive nickel foam and its use as a binder-free material in energy storage applications was assessed. The nanoplate-like NiCo2O4 nanostructure electrode was prepared by a simple chemical bath deposition method under optimized conditions. The NiCo2O4 electrode delivered an outstanding specific capacitance of 2791 F g-1 at a current density of 5 A g-1 in a KOH electrolyte in a three-electrode system as well as outstanding cycling stability with 99.1% retention after 3000 cycles at a current density of 7 A g-1. The as-synthesized NiCo2O4 electrode had a maximum energy density of 63.8 W h kg-1 and exhibited an outstanding high power density of approximately 654 W h kg-1. This paper reports a simple and cost-effective process for the synthesis of flexible high performance devices that may inspire new ideas for energy storage applications.

Perforated mesoporous NiO nanostructures for an enhanced pseudocapacitive performance with ultra-high rate capability and high energy density

The morphology of NiO (1D nanobelts and 2D nanosheets) has a significant effect on the pseudocapacitive performance. The perforated and interlinked mesoporous structure of NiO nanobelts delivered higher power and energy density than nanosheets.

Sonochemical synthesis of Co2SnO4 nanocubes for supercapacitor applications

In this work, a simple sonochemical route was followed to synthesize cobalt stannate (Co₂SnO₄) nanocubes using stannous and cobalt chlorides as the precursors in alkaline medium at room temperature. The structure, composition and surface morphology of synthesized Co₂SnO₄ nanocubes have been characterized by using X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) indicates that the Co₂SnO₄ nanocubes are crystalline, single-phase without any impurity phase; the sizes of nanocubes are ∼100 nm. The cyclic voltammetry, galvanostatic charge-discharge cycling test, and electrochemical impedance spectroscopy (EIS) measurements are carried out for the Co₂SnO₄ nanocubes shows a specific capacitance 237 F g^-1 at 0.5 mA cm^-2 current density and in 1 M Na₂SO₄ electrolyte. Co₂SnO₄ nanocubes exhibit long cycling life with 80% retention of initial capacitance after 2000 cycles and the excellent rate capability at 15 mA cm^-2 as much as 70% of that at 0.5 mA cm^-2 suggest its potential use for supercapacitor applications.

A high-performance supercapacitor electrode based on tremella-like NiC2O4@NiO core/shell hierarchical nanostructures on nickel foam

Tremella-like nickel oxalate@nickel oxide (NiC₂O₄@NiO) core/shell hierarchical nanostructures have been successfully synthesized on nickel foam, using Ni foam as a current collector, a Ni source and a three-dimensional (3D) substrate, through a facile hydrothermal method followed by an electrochemical activation process. The prepared samples can be directly used as binder-free electrodes for supercapacitors. The tremella-like morphology, together with the NiC₂O₄ nanoblocks on 3D Ni foam, significantly increases the amount of active sites for redox reactions and the conductivity of the electrode material, shortens the diffusion pathway for ions, facilitates the effective penetration of the electrolyte, and lowers the intrinsic equivalent series resistance, demonstrating good potential for energy storage application. This material has a high specific capacitance of 2287.09 F g^-1 at 1 A g^-1, a good cycling stability (remaining 95% after 10 000 cycles) and a good rate capability (83.2% retention upon increasing the current density by 10 times).

Role of fluorine surface modification in improving electrochemical cyclability of concentration gradient Li[Ni0.73Co0.12Mn0.15]O2 cathode material for Li-ion batteries

The fluorine-modified Li[Ni_0.73Co_0.12Mn_0.15]O_2−xF_x materials exhibit superior cycling stability, which is attributed to the synergistic protection of the surface NiO-like phase and fluoride layer.

Electrochemical Imprinted Polycrystalline Nickel-Nickel Oxide Half-Nanotube-Modified Boron-Doped Diamond Electrode for the Detection of L-Serine

This paper presents a novel and versatile method for the fabrication of half nanotubes (HNTs) using a flexible template-based nanofabrication method denoted as electrochemical imprinting. With use of this method, polycrystalline nickel and nickel(II) oxide (Ni-NiO) HNTs were synthesized using pulsed electrodeposition to transfer Ni, deposited by radio frequency magnetron sputtering on a porous polytetrafluoroethylene template, onto a boron-doped diamond (BDD) film. The Ni-NiO HNTs exhibited semicircular profiles along their entire lengths, with outer diameters of 50-120 nm and inner diameters of 20-50 nm. The HNT walls were formed of Ni and NiO nanoparticles. A biosensor for the detection of L-serine was fabricated using a BDD electrode modified with Ni-NiO HNTs, and the device demonstrated satisfactory analytical performance with high sensitivity (0.33 μA μM(-1)) and a low limit of detection (0.1 μM). The biosensor also exhibited very good reproducibility and stability, as well as a high anti-interference ability against amino acids such as L-leucine, L-tryptophan, L-cysteine, L-phenylalanine, L-arginine, and L-lysine.

Design and synthesis of hierarchical NiCo2S4@NiMoO4core/shell nanospheres for high-performance supercapacitors

A novel electrode material of three-dimensional hierarchical NiCo₂S₄@NiMoO₄core/shell nanospheres was synthesized by a facile two-step hydrothermal method. These hierarchical NiCo₂S₄@NiMoO₄core/shell nanospheres exhibit a high specific capacitance of 1714 F g⁻¹at a current density of 1 A g⁻¹, which indicated the excellent electrochemistry performance.