Abstract:A novel two-step electrodeposition method is presented to fabricate a high-performance CoS/graphene hybrid network with a nanosheet structure on Ni foam.
“…Finally, Fig. 4f reveals the C 2p spectrum; clearly, it shows one distinct peak at binding energy of 284.7 eV illustrating the existence of Sp 2 hybridized carbon atoms forming honeycomb, implying existence of graphene in the composite 33, 34 .Figure 4CV and GCD plots using three electrodes test results ( a ) CV plots of GNF/NCS/CNS core/shell at different scan rates, ( b ) comparison of CV plots of GNF/NCS/CNS core/shell, NF/NCS/CNS core/shell and NF/NCS at scan rate of 3 mV/S, ( c ) GCD plots of GNF/NCS/CNS core/shell at different current densities and ( d ) comparative GCD plots of GNF/NCS/CNS core/shell, NF/NCS/CNS core/shell and NF/NCS at current density of 10 mA/cm 2 .
…”
Three-dimensional (3D) core/shell structure of nickel cobalt sulfide is nano-engineered by using series of hydrothermal steps on a CVD grown graphene for supercapacitor application. This core/shell is composited of NiCo2S4 nanotube (NCS) as core and CoxNi(3−x)S2 (CNS) nanosheets as a shell. The as-synthesized composite exhibits excellent electrochemical properties by using the advantage of NCS nanontube core as superhighway for electron and ion transport, and CNS nanosheets shell as high active area pseudocapacitive material. The 3D graphene layer serves as excellent surface area to support 3D NCS/CNS; moreover, it provides excellent electrical conductivity between nickel foam current collector and the 3D NCS/NCS composite. Using these hybrid advantages the as-synthesized graphene/NCS/CNS composite electrode exhibits high areal capacitance of 15.6 F/cm2 at current density of 10 mA/cm2; excellent cycling stability of 93% after 5000 of cycles and excellent rate capability of 74.36% as current increase from 10 to 100 mA/cm2. Moreover, a prototype of asymmetric device fabricated using graphene/NCS/CNS as positive electrode and RGO as negative electrode exhibits high energy density of 23.9 Wh/kg and power density of 2460.6 W/kg at high operating current of 100 mA. Such high performance electrode material may get great application in future energy storage device.
“…Finally, Fig. 4f reveals the C 2p spectrum; clearly, it shows one distinct peak at binding energy of 284.7 eV illustrating the existence of Sp 2 hybridized carbon atoms forming honeycomb, implying existence of graphene in the composite 33, 34 .Figure 4CV and GCD plots using three electrodes test results ( a ) CV plots of GNF/NCS/CNS core/shell at different scan rates, ( b ) comparison of CV plots of GNF/NCS/CNS core/shell, NF/NCS/CNS core/shell and NF/NCS at scan rate of 3 mV/S, ( c ) GCD plots of GNF/NCS/CNS core/shell at different current densities and ( d ) comparative GCD plots of GNF/NCS/CNS core/shell, NF/NCS/CNS core/shell and NF/NCS at current density of 10 mA/cm 2 .
…”
Three-dimensional (3D) core/shell structure of nickel cobalt sulfide is nano-engineered by using series of hydrothermal steps on a CVD grown graphene for supercapacitor application. This core/shell is composited of NiCo2S4 nanotube (NCS) as core and CoxNi(3−x)S2 (CNS) nanosheets as a shell. The as-synthesized composite exhibits excellent electrochemical properties by using the advantage of NCS nanontube core as superhighway for electron and ion transport, and CNS nanosheets shell as high active area pseudocapacitive material. The 3D graphene layer serves as excellent surface area to support 3D NCS/CNS; moreover, it provides excellent electrical conductivity between nickel foam current collector and the 3D NCS/NCS composite. Using these hybrid advantages the as-synthesized graphene/NCS/CNS composite electrode exhibits high areal capacitance of 15.6 F/cm2 at current density of 10 mA/cm2; excellent cycling stability of 93% after 5000 of cycles and excellent rate capability of 74.36% as current increase from 10 to 100 mA/cm2. Moreover, a prototype of asymmetric device fabricated using graphene/NCS/CNS as positive electrode and RGO as negative electrode exhibits high energy density of 23.9 Wh/kg and power density of 2460.6 W/kg at high operating current of 100 mA. Such high performance electrode material may get great application in future energy storage device.
“…30 value for high-performance supercapacitors. 13,22 To further analyze the electron transfer properties of the Ni-Co based electrode materials, electrochemical impedance spectroscopy (EIS) has been tested by using Nyquist plots (Figure 4b, inset).…”
Nickel-cobalt oxides/hydroxides have been considered as promising electrode materials for a high-performance supercapacitor. However, their energy density and cycle stability are still very poor at high current density. Moreover, there are few reports on the fabrication of mixed transition-metal oxides with multishelled hollow structures. Here, we demonstrate a new and flexible strategy for the preparation of hollow Ni-Co-O microspheres with optimized Ni/Co ratios, controlled shell porosity, shell numbers, and shell thickness. Owing to its high effective electrode area and electron transfer number (n(3/2) A), mesoporous shells, and fast electron/ion transfer, the triple-shelled Ni-Co1.5-O electrode exhibits an ultrahigh capacitance (1884 F/g at 3A/g) and rate capability (77.7%, 3-30A/g). Moreover, the assembled sandwiched Ni-Co1.5-O//RGO@Fe3O4 asymmetric supercapacitor (ACS) retains 79.4% of its initial capacitance after 10 000 cycles and shows a high energy density of 41.5 W h kg(-1) at 505 W kg(-1). Importantly, the ACS device delivers a high energy density of 22.8 W h kg(-1) even at 7600 W kg(-1), which is superior to most of the reported asymmetric capacitors. This study has provided a facile and general approach to fabricate Ni/Co mixed transition-metal oxides for energy storage.
“…All the diffraction peaks are well matched with literature. [30,31] Crystallinity of CuCo 3 S z synthesized on carbon cloth is determined with the help of Raman spectroscopy. The presence of a broad peak at 3444 cm À 1 is assigned due to OÀ H stretching of surface adsorbed H 2 O molecules.…”
Section: Structural Morphological and Electronic Characterization Omentioning
When designing a device for energy conversion, development of a highly active catalyst for OER (oxygen evolution reaction) reaction in alkaline medium is of utmost importance. For energy conversion, herein, we developed copper cobalt sulfide on carbon cloth (CC) using a simple and facile hydrothermal method. A vertically grown 2D sheet-like structure of coppercobalt sulfide is observed using L-cysteine as a sulfur source. An optimized ratio of copper(II) and cobalt(III) and the best sulfur source are found to boost the electrocatalytic activity of mixed metal thiospinel for OER. Several characterization techniques (XRD, Raman, FESEM, TEM, XPS, and ICP-AES) were used to confirm phase purity, morphology, and composition of copper cobalt sulfides. We have established that 2D nanosheets of CuCo 3 S z /CC exhibited superior electrocatalytic performance over bare RuO 2 in 1.0 M KOH solution. It is observed that CuCo 3 S z /CC need only 105 mV overpotential to generate 5 mA/ cm 2 current density. CuCo 3 S z /CC is very stable and able to produce unaltered current density under an applied potential of 1.615 V vs. RHE for 48 h. Electrochemically active surface area calculation is performed for all catalysts to confirm higher electrocatalytic activity. The catalyst, CuCo 3 S z /CC is used in a broad pH region using 0.5 M KOH, saline water, and 0.5 M Na 2 SO 4 electrolyte solution to widen the applicability of water splitting. This work shows an avenue to develop active and durable electrocatalyst for OER without using any noble metal electrocatalyst.[a] C.
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