Three-dimensional NiMoO4@CoWO4 core–shell nanorod arrays for electrochemical energy storage applications

Abstract

In this paper, NiMoO₄@CoWO₄ core–shell nanostructures have been synthesized by a hydrothermal process and annealing. Structural characterization and compositional analysis of the as-prepared NiMoO₄@CoWO₄ nanocomposites were performed using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, galvanostatic charge–discharge cycling, and electrochemical impedance spectroscopy. Here, NiMoO₄@CoWO₄ nanostructures were designed and synthesized on Ni foam. NiMoO₄ nanorods would provide electron “superhighways” for charge storage and delivery, which could provide an effective electrical connection to the CoWO₄ electrode material. In addition, the open space between these nanosheets can increase the active sites and the contribution of capacitive effects. Finally, NiMoO₄@CoWO₄ directly grown on Ni foam could avoid the “dead” volume caused by the tedious process of mixing active materials with polymer binders/conductive additives. As expected, NiMoO₄@CoWO₄ exhibited high specific capacity, good rate performance and excellent electrochemical stability. The results show that NiMoO₄@CoWO₄ exhibited a high specific capacity at a current density of 5 mA cm⁻² and splendid electrochemical stability (88.5% retention after 4000 cycles). The great electrochemical performance could be ascribed to the unique core–shell architecture and the synergistic effect from the NiMoO₄ nanorods and CoWO₄.