Ni3S2@CoS core–shell nano-triangular pyramid arrays on Ni foam for high-performance supercapacitors

Abstract

In this study, we demonstrate a facile method to fabricate novel Ni₃S₂ nano-triangular pyramid (NTP) arrays on Ni foam through a hydrothermal process and build unique Ni₃S₂@CoS core–shell NTP arrays by electro-deposition. The obtained Ni₃S₂@CoS material displays twice the specific capacitance of the pure Ni₃S₂ material in both a three-electrode system (4.89 F cm⁻² at 4 mA cm⁻²) and asymmetric supercapacitor device (0.69 F cm⁻² at 1.43 mA cm⁻²). In addition, the asymmetric supercapacitor demonstrates the outstanding energy density of 28.24 W h kg⁻¹ at a power density of 134.46 W kg⁻¹, with a stable cycle life (98.83% retained after 2000 cycles). The unique structure of the Ni₃S₂@CoS core–shell NTP arrays, which provides an ultra-thin CoS shell to enlarge efficient areas, introduces good conductivity, and short transportation lengths for both ions and electrons, contributes most to its excellent performance. Moreover, the bare Ni₃S₂ NTP arrays can be used as a new template to build other potential electrode materials.