Abstract
The novel hierarchical Ni-Co sulfide nanosheet-nanotubes arrays were directly grown on Ni foam, as binder-free electrodes, have been successfully synthesized following a one-step facile hydrothermal method combined with a sulfide treatment. The initial value of the area capacitance achieved 2.28 F cm−2 at a current density of 1 mA cm−2. A high areal capacitance retention of 95.2% compared to activation-induced peak value is achieved after 3000 charge-discharge cycles, which is much better than counter Ni-Co oxide electrode (1.75 F cm−2 at 1 mA cm−2, 93.2% retention compared to activation induced peak value). The outstanding and excellent super capacitive performance is ascribed to ion-exchange reaction, which induces a flexible hollow nanotube feature and show higher conductivity, compared with Ni-Co oxide NWs. Cyclic voltammetry (CV) and Electrochemical impedance spectra (EIS) results confirmed that the synthesized electrode contains the lowest resistance at high, and at lower frequency, leading to easy penetration of electrolytes and fast transportation of electrons inside the electrode. In this proposed work, a one-step hydrothermal method has been followed, and provided for the sulfide-induced, with a noticeable electrochemical performance of nickel cobaltite compounds and supplying a promising route for high-performance supercapacitor electrodes.
Highlights
In recent years, sustainable energy and green energy systems get considerable attention to meet the increasing demand for energy throughout the world
1 measured as I (mA) cm−2 current density is achieved after 3000 charge-discharge cycles, which is much better than counter Ni-Co oxide electrode
Our results indicate that the Ni-Co sulfide nanosheet-nanotubes arrays can act as high-performance electrode materials in supercapacitors
Summary
Sustainable energy and green energy systems get considerable attention to meet the increasing demand for energy throughout the world. The metal oxides, as pseudo-capacitance materials, preserving much higher capacitance owing to the more charge storage at surface, get great interest and are widely investigated, due to their high theoretical capacitance for supercapacitors The fabrication of these compounds, and especially oxides materials with diverse structures and morphologies, have attracted significant interest in material science and at an industry level. The chemical and physical properties of transition metal sulfides are directly related to surface morphology, structure, and the size of the materials The fabrication of these compounds, and especially sulfides material similar to oxides materials with diverse structures and morphologies, have attracted significant interest for developing electrode materials for energy storage devices [22]. Our results indicate that the Ni-Co sulfide nanosheet-nanotubes arrays can act as high-performance electrode materials in supercapacitors
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