One-pot hydrothermal synthesis of reduced graphene oxide/carbon nanotube/α-Ni(OH)_2 composites for high performance electrochemical supercapacitor

摘要

Reduced graphene oxide/carbon nanotube/α-Ni(OH)_2 (RG0/CNT/α-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 α-Ni(OH)_2 nanopartides 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/ α-Ni(OH)_2 composite (GC2Ni2) 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 GC2Ni2 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 electroactive materials during charge-discharge process.