Self-Assembled Hierarchical Silkworm-Type Bimetallic Sulfide (NiMo₃S₄) Nanostructures Developed on S-g-C₃N₄ Sheets: Promising Electrode Material for Supercapacitors

An electrode material composed of bimetallic sulfides on g-C 3 N 4 typically enhances the energy storage capacity of devices due to the merits of each component, but it still suffers from low energy density over long cycles. Although Ni-based bimetallic sulfides have become good electrode materials for supercapacitors, practical applications of these materials are hindered due to unsatisfactory cycling stability. Here, we demonstrate a simple two-step in situ approach to prepare bimetallic sulfide nanobulbs on a sulfur-doped graphitic carbon nitrate matrix for a NiMo 3 S 4 @S-g-C 3 N 4 composite, which is further used for supercapacitor devices. A small amount of sulfur doping to g-C 3 N 4 enhances the conducting channels for electron transportation. An NMS@S-gC nanocomposite clearly shows the formation of small nanobulbs that are formed as silk warm-type hierarchical morphology structures and these were wrapped on the surface of S-gC porous nanosheets. The device made up of these composites exhibited a maximum specific capacitance of 142.4 F g –1, a high energy density of 41.4 Wh kg –1, and a power density of 723.5 W kg –1 at a current density of 1 A g –1 . Meanwhile, in a three-electrode device configuration, the working electrode demonstrates a specific capacitance of 934.2 F g –1 at 1 A g –1, which is 1.6 times greater than that of bare NiMo 3 S 4 . Moreover, the capacitance retention of the device is about 91% even after 5000 cycles at 8 A g –1 . The results obtained in this investigation surpassed most reported metallic sulfides on g-C 3 N 4 . Hence, this work could give a different pathway for the synthesis of electrode materials for energy storage devices.