Synergy of PVP and ethanol to synthesize Ni3S4 quantum dots for high-performance asymmetric supercapacitors

Abstract

Ni₃S₄ quantum dots (QDs) have great potential for supercapacitors due to their unique quantum effects, high specific surface area, high water solubility and good stability, but the current preparation process is cumbersome and toxic. Here, we highlight a facile and environmentally-friendly synthesis of Ni₃S₄ QDs for the first time by virtue of the synergy of polyvinylpyrrolidone (PVP) and ethanol. The synergistic mechanism was revealed by using XRD to investigate the effect of the synthesis solvent. When QDs were used as a supercapacitor electrode material they exhibited excellent electrochemical properties, and the specific capacitance at 1 A g⁻¹ was 1440 F g⁻¹. In addition, Ni₃S₄ QDs and activated carbon (AC) are assembled into a Ni₃S₄ QD//AC asymmetric supercapacitor (ASC), which delivered a maximum energy density of 60.4 W h kg⁻¹. This work provides new ideas for the preparation of QDs and opens up new concepts for the synthesis of nickel sulfide.