One pot and large-scale synthesis of nanostructured metal sulfides: Synergistic effect on supercapacitor performance

Metal sulfides received key interest as an electrode material for storage and conversion of energy. Here, the novel nanostructured N17S18 and (CoNi)(3)S-4 materials were synthesized via one-step hydrothermal method, and the synergistic effect of metal ions and electrochemical properties was investigated. A new and simple solution growth technique was employed in this work. The prepared nanopowders were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy techniques. The X-ray diffraction analysis of the prepared nanopowder revealed the formation of cubic phase cobalt nickel sulfides (CoNi)(3)S-4 and hexagonal phase nickel sulfides (Ni17S18). Scanning electron microscopy analysis display fibrous, flakes and sheet-like morphology for CoxSx, N17S18 and (CoNi)(3)S-4, respectively. Fibrous and sheet-like morphology exhibits higher electrochemical performance in supercapacitors. The electrochemical behavior of the amorphous CoxSx, crystallite Ni17S18 and (CoNi)(3)S-4 modified electrodes was investigated using electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge-discharge techniques. The specific capacitance of 57 F/g and 31 F/g were obtained for the amorphous CoxSx and crystalline (CoNi)(3)S-4 powder, respectively. Amorphous CoxSx modified electrode retains 76% of initial capacitance after 1000 repeated cycling process. These results of this study suggest that the CoxSx and crystalline (CoNi)(3)S-4 are appropriate materials for supercapacitor applications.