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

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.