Hierarchical NiO Microflowers for High Performance Supercapacitors

Hierarchical NiO-microstructures including microflowers are synthesized on the surface of copper foams via hydrothermal precipitation. The surface morphology and structure of the NiO-microstructures are investigated by scanning electron microscopy and x-ray diffraction spectroscopy. The electrochemical performance of a three-electrode system with the NiO-microstructures as the working electrode is characterized. The three-electrode system with the NiO-microflowers synthesized with 6 h exhibits a specific capacitance of 3435.5 F/g at the electric current density of 0.5 A/cm² and the capacitance retention of 53.3% after 100 cycles. Large retentions of ∼ 95.4% and ∼ 100% for the NiO-microstructures made with hydrothermal times of 3 h and 24 h are achieved, respectively.