Porous and Hierarchically Structured Ammonium Nickel Molybdate/Nickel Sulfide/Reduced Graphene Oxide Ternary Composite as High Performance Electrode for Supercapacitors

Abstract

AbstractA novel ternary composite composed of ammonium nickel molybdate, nickel sulfide and reduced graphene oxide (ANM‐NiS‐rGO) has been synthesized by using a two‐step hydrothermal method for the first time. The morphological analysis reveals that the rGO nanosheets in the ternary composite are decorated with the electrochemically active NiS nanoparticles and ANM microflowers. Because the ternary composite exhibits a porous and 3D flower‐like structures, it possesses the large surface area of 135 m2 g−1 and high pore volume of 0.258 cm3 g−1. On the other hand, ANM‐NiS‐rGO was investigated as positive electrode for battery‐type hybrid supercapacitor that shows a specific capacity of 150 mAh g−1 at a current density of 1 A g−1. For comparison, the corresponding components such as ANM‐rGO and NiS‐rGO were also investigated. It was found that the ternary composite shows a higher specific capacity, better rate capability and cyclic stability compared with the binary composites as the former possesses higher surface area and electrical conductivity. To demonstrate the practical applications, a hybrid supercapacitor was fabricated by using ANM‐NiS‐rGO and rGO as the positive and negative electrodes, respectively. This device can be operated in the voltage range of 0–1.75 V and shows a high specific capacity of 28 mAh g−1 at a current density of 2 Ag−1. Furthermore, the device delivers a maximum energy density of 24.2 Wh kg−1 at a power density of 1.75 kW kg−1. These results suggest that the porous and hierarchically structured ANM‐NiS‐rGO has high potential in practical energy storage applications.