Ni nanoparticles@Ni–Mo nitride nanorod arrays: a novel 3D-network hierarchical structure for high areal capacitance hybrid supercapacitors

Abstract

Because of the advanced nature of their high power density, fast charge/discharge time, excellent cycling stability, and safety, supercapacitors have attracted intensive attention for large-scale applications. Nevertheless, one of the obstacles for their further development is their low energy density caused by sluggish redox reaction kinetics, low electroactive electrode materials, and/or high internal resistance. Here, we develop a facile and simple nitridation process to successfully synthesize hierarchical Ni nanoparticle decorated Ni_0.2Mo_0.8N nanorod arrays on a nickel foam (Ni–Mo–N NRA/NF) from its NiMoO₄ precursor, which delivers a high areal capacity of 2446 mC cm⁻² at a current density of 2 mA cm⁻² and shows outstanding cycling stability. The superior performance of the Ni–Mo–N NRA/NF can be ascribed to the metallic conductive nature of the Ni–Mo nitride, the fast surface redox reactions for the electrolyte ions and electrode materials, and the low contacted resistance between the active materials and the current collectors. Furthermore, a hybrid supercapacitor (HSC) is assembled using the Ni–Mo–N NRA/NF as the positive electrode and reduced graphene oxide (RGO) as the negative electrode. The optimized HSC exhibits excellent electrochemical performance with a high energy density of 40.9 W h kg⁻¹ at a power density of 773 W kg⁻¹ and a retention of 80.1% specific capacitance after 6000 cycles. These results indicate that the Ni–Mo–N NRA/NF have a promising potential for use in high-performance supercapacitors.