One-step synthesis of hierarchical structured nickel copper sulfide nanorods with improved electrochemical supercapacitor properties

Nanorods-like structured ternary metal sulfides of Ni1-xCuxS with various compositions (x = 0.1, 0.2 and 0.3), and binary sulfides of NiS and Cu9S5 were synthesised via a single-step hydrothermal process. The structural properties and the functional groups of the synthesized materials were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) studies. Surface structure and chemical composition of the samples were inspected using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDAX). The electrochemical properties of the as-synthesised metal sulfide based electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) analyses and the maximum specific capacitance (SC) of similar to 1092 F/g was achieved for the Ni-0.8Cu0.2S at a current density of 15 mA/g, while pure NiS and Cu9S5 electrodes showed the minimum SC of similar to 575 and similar to 70 F/g, respectively. Further, the electrochemical impedance studies (EIS) revealed low R-ct value (3.4 omega) for the Ni-0.8Cu0.2S electrode and improved electrochemical supercapacitor properties of Ni-0.8Cu0.2S electrode because of to the synergistic effect and its well crystalline nanorods structure which offers more electrochemical active sites for faradaic reactions and fast electrolyte ions diffusion in to electrode. Additionally, the stability performance of the Ni-0.8Cu0.2S electrode was performed at a fixed current density of 20 mA/g, and the Ni-0.8Cu0.2S sample possesses the good cycling stability with the retention of 80% capacitance after 3000 GCD cycles. These results demonstrate that the as-synthesised binary and ternary metal sulfides are suitable cost effective and pollution free electrode materials for supercapacitors.