Construction of Hierarchical CuO/Cu₂O@NiCo₂S₄ Nanowire Arrays on Copper Foam for High Performance Supercapacitor Electrodes.

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 at 10 mA cm, good rate capability (82.06% capacitance retention at the current density from 2 to 50 mA cm) and excellent cycling stability, with capacitance retention of 96.73% after 2000 cycles at 10 mA cm. 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.