Sequential partial ion exchange synthesis of composite Ni3S2/Co9S8/NiSe nanoarrays with a lavender-like hierarchical morphology

Abstract

A series of hierarchical nanoarrays with a lavender-like structure was synthesized via a facile in situ hydrothermal method by sequential partial ion exchange. Hierarchical Ni@Ni₃S₂ nanoarrays that were partially surrounded with nanoflakes were first fabricated by simultaneously using Ni foam as a template and as a source. The hierarchical structure was composed of one-dimensional rods combined with two-dimensional nanoflakes. Furthermore, Co and Se ions, as the beneficial cation and anion, were successfully introduced into the hierarchical Ni@Ni₃S₂ material by sequential partial ion exchange. This reaction formed Ni@Ni₃S₂/Co₉S₈ and Ni@Ni₃S₂/Co₉S₈/NiSe composite multilevel electrodes with structures that were similar to those of the parent materials. All the as-prepared materials were assembled into asymmetric supercapacitor devices to explore their electrochemical performance. Compared with single-component Ni@Ni₃S₂, the Ni@Ni₃S₂/Co₉S₈/NiSe//active carbon device exhibited a better rate performance of 78.93 F g⁻¹ at a current density of 1 A g⁻¹ (retaining 75% from 1 A g⁻¹ to 10 A g⁻¹). This device still delivered an energy density of 17.75 Wh kg⁻¹ even at a high power density of 1945.2 W kg⁻¹. This finding demonstrated that Ni@Ni₃S₂/Co₉S₈/NiSe is a promising electrode material for supercapacitors.