Tuning the electrochemical properties of NiS2 2D-nanoflakes by one-zone sulfurization for supercapacitor applications

Abstract

Nickel-based sulfides (particularly NiS _2 ) are regarded as promising materials for highly efficient electrochemical generation and storage devices. The conventional fabrication methods of nanostructured NiS _X electrodes involve several complex steps using multiple precursors and techniques. In this paper, the NiS _X electrodes are prepared by a plain one-step process of one-zone sulfurization of Ni foam. The evolution of highly electroactive 2D-nanoflakes reliant on sulfurization temperature is studied. Scanning electron microscopy, x-ray diffractometry, and energy-dispersive x-ray spectroscopy confirmed the presence of NiS _X (x = 1 and 2) in the prepared structures. A strong dependence of sample morphology and 2D-nanoflakes density on sulfurization temperature was demonstrated. The electrochemical properties of samples were characterized by cyclic voltammetry and electrochemical impedance spectroscopy measurements. Owing to the 2D-nanoflake structure, the NiS _2 showed attractive electrochemical performance, including a high specific capacitance of 648 mF cm ^−2 and a capacitance retention rate of 90,7% after 3000 cycles. Our study shows that the composition and crystal growth of NiS _X can be tuned by reaction temperature during the sulfurization and high perspective of sulfurization in the synthesis of highly electroactive large-scale electrodes for supercapacitors.

Keywords

• NiS2
• 2D-nanoflakes
• sulfurization
• morphology
• supercapacitor