Hierarchical Ni3S2 nanorod@nanosheet arrays on Ni foam for high-performance supercapacitor.

We successfully designed and prepared hierarchical Ni3S2 nanosheet@nanorod arrays on three-dimensional Ni foam via facile hydrothermal sulfuration. We conducted a series of time- and temperature-dependent experiments to determine the Ostwald ripening process of hierarchical Ni3S2 nanosheet@nanorod arrays. The rationally hierarchical architecture creates an excellent supercapacitor electrode for Ni3S2 nanosheet@nanorod arrays. The areal capacitance of this array reaches 5.5 F cm-2 at 2 mA cm-2, which is much higher than that of Ni3S2 nanosheet arrays (1.5 F cm-2). The corresponding asymmetric supercapacitor exhibits a wide potential window of 1.6 V and energy density up to 1.0 Wh cm-2 when the proposed array is utilized as the positive electrode with activated carbon as the negative electrode. This electrochemical performance enhancement is attributable to the hierarchical structure and synergistic cooperation of macroporous Ni foam and well-aligned Ni3S2 nanosheet@nanorod arrays. Our results represent a promising approach to the preparation of hierarchical nanosheet@nanorod arrays as high-performing electrochemical capacitors.