One-pot hydrothermal synthesis of reduced graphene oxide/carbon nanotube/α-Ni(OH)2 composites for high performance electrochemical supercapacitor

Reduced graphene oxide/carbon nanotube/a-Ni(OH)(2) (RGO/CNT/alpha-Ni(OH)(2)) composites are successfully synthesized by a one-pot hydrothermal route. The structural characterization of the composites by EDX, XRD, FT-IR, XPS, Raman, FESEM and TEM indicate that alpha-Ni(OH)(2) nanoparticles with the size around 5 nm are randomly decorated onto three-dimensional (3D) hierarchical structure RGO/CNT. The electrochemical performances of the composites are evaluated by cyclic voltammogram, galvanostatic charge -discharge and electrochemical impedance spectroscopy. Interestingly, it is found that the electrochemical capacitance of the composites depends on the amount of CNTs to a large extent and RGO/CNT/ alpha-Ni(OH)(2) composite (GC2Ni(2)) with optimized ratio exhibits the high specific capacitance of 1320 F g(-1), at 6 A g(-1). In addition, the cycling measurements show that GC(2)Ni(2) maintains a specific capacitance of 1008 F g(-1) at 15 A g(-1) after 1000 cycles corresponding to a reduction of capacitance of about 7.8%. The enhancement in specific capacitance and cycling stability is believed to be due to the 3D RGO/CNT conductive network which promotes not only efficient charge transport and facilitates the electrolyte diffusion, but also prevents effectively the volume expansion/contraction and aggregation of electro-active materials during charge-discharge process. (C) 2013 Published by Elsevier B.V.