Hydrothermal synthesis of NiCo ₂ O ₄ nanowires/nitrogen-doped graphene for high-performance supercapacitor

NiCo ₂ O ₄ nanowires/nitrogen-doped graphene (NCO/NG) composite materials were synthesized by hydrothermal treatment in a water-glycerol mixed solvent and subsequent thermal transformation. The obtained materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The electrochemical performance of the composites was evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrum techniques. NiCo ₂ O ₄ nanowires are densely coated by nitrogen-doped graphene and the composite displays good electrochemical performance. The maximum specific capacitance of NCO/NG is 1273.13 F g ^-1 at 0.5 A g ^-1 in 6 M KOH aqueous solution, and it exhibits good capacity retention without noticeable degradation after 3000 cycles at 4 A g ^-1 .