Porous nanorods of nickel-cobalt double hydroxide prepared by electrochemical co-deposition for high-performance supercapacitors.

Nickel-cobalt double hydroxides (Ni-Co DHs) combined with cost-effectively commercial expanded graphite (EG) was prepared via a facile in-situ electrodeposition in mixed solvents of N,N-dimethylformamide and water. By simply adjust molar ratios of Ni2+/Co2+, a Ni-Co DHs/EG electrode in which Ni-Co DHs showing a porous-nanorod microstructure was fabricated. Thanks to synergistic effects between Ni(OH)2 and Co(OH)2 as well as the unique morphology of porous nanorods, an optimal Ni-Co DHs/EG electrode with a total mass loading of 4.0 mg cm-2 can deliver a specific capacitance of 1246 F g-1 at 1 A g-1, a rate capability of 91.8% as the discharging current density increasing from 1 to 10 A g-1, and a capacitance retention of 80.1% after 1000 cycles charged/discharged at 10 A g-1. Thus we can draw a conclusion that the Ni-Co DHs/EG electrode possesses a satisfactory specific capacitance, extremely superior rate performance, and good cycle stability, therefore it can be very competitive for practical applications in supercapacitors.