Nanoforest of hierarchical core/shell CuO@NiCo₂O₄ nanowire heterostructure arrays on nickel foam for high-performance supercapacitors

Nickel foam-supported CuO@NiCo₂O₄ nanoforests with a mesoporous hierarchical core/shell structure are prepared by combining a facile, scalable, and cost-effective thermal oxidation method with a simple hydrothermal method followed by a calcination procedure. The smart hybridization of CuO nanowires and NiCo₂O₄ nanosheets into a hierarchical core/shell array configuration results in remarkably enhanced electrochemical performances with high specific capacitance, excellent rate capability and good cycle performance compared with pure nickel foam-supported NiCo₂O₄ nanosheets. A high specific capacitance of 1298.8 F g⁻¹ at a current density of 1 A g⁻¹ has been exhibited and excellent rate capability of about 96.3% capacitance retention at 5 A g⁻¹ can be obtained. The CuO@NiCo₂O₄-based supercapacitor exhibits a very long cycle life with only 2.1% capacitance loss after 2000 cycles and the coulombic efficiency remains about 100% during the cycling. In addition, the assembled CuO@NiCo₂O₄//AC ASC device delivers an energy density of 27.9 W h kg⁻¹ at a power density of 749.6 W kg⁻¹, and the energy density is as much as 17.7 W h kg⁻¹ even at a high power density of 7496.5 W kg⁻¹. These excellent electrochemical performances demonstrate that the nickel foam-supported hierarchical core/shell CuO@NiCo₂O₄ nanowire heterostructure array electrodes are highly desirable for application as advanced supercapacitor electrodes.