Abstract
Hierarchical copper oxide @ ternary nickel cobalt sulfide (CuO/Cu2O@NiCo2S4) core-shell nanowire arrays on Cu foam have been successfully constructed by a facile two-step strategy. Vertically aligned CuO/Cu2O nanowire arrays are firstly grown on Cu foam by one-step thermal oxidation of Cu foam, followed by electrodeposition of NiCo2S4 nanosheets on the surface of CuO/Cu2O nanowires to form the CuO/Cu2O@NiCo2S4 core-shell nanostructures. Structural and morphological characterizations indicate that the average thickness of the NiCo2S4 nanosheets is ~20 nm and the diameter of CuO/Cu2O core is ~50 nm. Electrochemical properties of the hierarchical composites as integrated binder-free electrodes for supercapacitor were evaluated by various electrochemical methods. The hierarchical composite electrodes could achieve ultrahigh specific capacitance of 3.186 F cm−2 at 10 mA cm−2, good rate capability (82.06% capacitance retention at the current density from 2 to 50 mA cm−2) and excellent cycling stability, with capacitance retention of 96.73% after 2000 cycles at 10 mA cm−2. These results demonstrate the significance of optimized design and fabrication of electrode materials with more sufficient electrolyte-electrode interface, robust structural integrity and fast ion/electron transfer.
Highlights
Over the past few years, considerable effort has been made to search for clean, efficient and renewable energy sources due to the limited available fossil fuels and serious pollution problems caused by conventional energy technologies [1,2,3,4]
Considerable progress has been achieved so far in SC applications, they are still restricted by their lower energy density in comparison with secondary batteries
X-ray diffraction (XRD) patterns were recorded on a Rigaku D/MAX 2550 diffractometer (Rigaku Corporation, Tokyo, Japan) equipped with a Cu Kα radiation generator
Summary
Over the past few years, considerable effort has been made to search for clean, efficient and renewable energy sources due to the limited available fossil fuels and serious pollution problems caused by conventional energy technologies [1,2,3,4]. Carbon-based materials, conducting polymers and transition metal oxides/hydroxides, are among the most extensively investigated electrode materials for SCs [9,10,11,12] They have some obvious drawbacks, including low specific capacitance, poor cycling stability and low electronic conductivity, which inevitably deteriorate their electrochemical performance and restrict their applications in SCs. it is imperative to develop advanced composites combining synergistic contributions from single components to maximize the performance of electrodes. A significant advance has been made in the fabrication of ternary metal sulfides based 3D core-shell composites, they still suffer from significant degradation during the fast and long-term cycling process due to structural or morphological failure, which greatly limits their electrochemical performance. The relationship between structural and electrochemical properties of the composites is studied systematically
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