5 research outputs found

    Highly Efficient Removal of Organic Dyes from Waste Water Using Hierarchical NiO Spheres with High Surface Area

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    A facile solvothermal method has been developed for large-scale preparation of uniform spheres of a nickel–ethylene glycol complex (Ni-EG complex) with a hierarchical nanostructure. The dispersibility and hierarchical structure of the Ni-EG particles can be tuned by varying the concentration of additives added. On the basis of experimental observations, a plausible mechanism has been proposed to understand the formation process of the Ni-EG complex spheres. Calcining these as-prepared Ni-EG complex spheres at 300 °C in air results in uniform porous NiO spheres with a high specific surface area of 222 m<sup>2</sup> g<sup>–1</sup>. When served as the adsorbent for Congo red in water, the colloidal suspension of the as-prepared NiO hierarchical spheres exhibits a high adsorption capacity for the dye removal, suggesting their potential use in water treatment

    Rational Design of Self-Supported Ni<sub>3</sub>S<sub>2</sub> Nanosheets Array for Advanced Asymmetric Supercapacitor with a Superior Energy Density

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    We report a rationally designed two-step method to fabricate self-supported Ni<sub>3</sub>S<sub>2</sub> nanosheet arrays. We first used 2-methylimidazole (2-MI), an organic molecule commonly served as organic linkers in metal–organic frameworks (MOFs), to synthesize an α-Ni­(OH)<sub>2</sub> nanosheet array as a precursor, followed by its hydrothermal sulfidization into Ni<sub>3</sub>S<sub>2</sub>. The resulting Ni<sub>3</sub>S<sub>2</sub> nanosheet array demonstrated superior supercapacitance properties, with a very high capacitance of about 1,000 F g<sup>–1</sup> being delivered at a high current density of 50 A g<sup>–1</sup> for 20,000 charge–discharge cycles. This performance is unparalleled by other reported nickel sulfide-based supercapacitors and is also advantageous compared to other nickel-based materials such as NiO and Ni­(OH)<sub>2</sub>. An asymmetric supercapacitor was then established, exhibiting a very stable capacitance of about 200 F g<sup>–1</sup> at a high current density of 10 A g<sup>–1</sup> for 10,000 cycles and a surprisingly high energy density of 202 W h kg<sup>–1</sup>. This value is comparable to that of the lithium-ion batteries, i.e., 180 W h kg<sup>–1</sup>. The potential of the material for practical applications was evaluated by building a quasi-solid-state asymmetric supercapacitor which showed good flexibility and power output, and two of these devices connected in series were able to power up 18 green light-emitting diodes

    Stainless Steel Mesh-Supported NiS Nanosheet Array as Highly Efficient Catalyst for Oxygen Evolution Reaction

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    Nickel­(II) sulfide (NiS) nanosheets with a thickness of 10 nm and a size of 200 nm were facilely grown on stainless steel (SLS) meshes via a one-pot hydrothermal method. This unique construction renders an excellent electrical contact between the porous film of active NiS sheets and the highly conductive substrate, which exhibits a superior catalytic activity toward oxygen evolution reaction (OER). The NiS@SLS electrocatalyst exhibits an unusually low overpotential of 297 mV (i.e., 1.524 V vs RHE) at a current density of 11 mA·cm<sup>–2</sup>, and an extra small Tafel slope of only 47 mV·dec<sup>–1</sup> proves an even more competitive performance at high to very high current densities. This performance compares very favorably to other Ni-based catalysts and even to the precious state-of-the-art IrO<sub>2</sub> or RuO<sub>2</sub> catalyst

    H<sub>2</sub>O–EG-Assisted Synthesis of Uniform Urchinlike Rutile TiO<sub>2</sub> with Superior Lithium Storage Properties

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    A facile green method to synthesize uniform nanostructured urchinlike rutile TiO<sub>2</sub> is demonstrated. Titanium trichloride was selected as the TiO<sub>2</sub> precursor, and a mixed solvent containing H<sub>2</sub>O and ethylene glycol was used. By using this binary medium, the nucleation and crystal growth of rutile TiO<sub>2</sub> can be regulated, giving rise to very uniform urchinlike structures with tailorable sizes. As confirmed by the SEM and TEM analysis, large particles with dense aggregation of needle-like building blocks or small ones with loosely packed subunits could be obtained at different reaction conditions. The as-prepared samples were applied as the anode material for lithium-ion batteries, and they were shown to have superior properties with a high reversible capacity of 140 mA h g<sup>–1</sup> at a high current rate of 10 C for up to 300 cycles, which is almost unmatched by other rutile TiO<sub>2</sub>-based electrodes. A stable capacity of 88 mA h g<sup>–1</sup> can also be delivered at an extremely high rate of 50 C, suggesting the great potential of the as-prepared product for high-rate lithium-ion batteries
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