Hydrothermal Synthesis of CoMoO4/Co9S8 Nanorod Arrays on Nickel Foam for High-Performance Asymmetric Supercapacitors with High Energy Density

Abstract

CoMoO4/Co9S8 nanorod arrays supported on nickel foam are successfully assembled via a facile two-step hydrothermal route. Due to the unique nanorod array structure, the CoMoO4/Co9S8, as the electrode, possesses a high capacity 1.54mA h·cm−2 (343.21mA h·g−1) and a large capacitance 9.17Fcm−2 (2059.26Fg−1) at a current density of 20 mA·cm−2 (4.44 A·g−1), and an excellent cycling stability (8.6% degradation after 3000 cycles). The asymmetric supercapacitor based on the CoMoO4/Co9S8 nanorod arrays as a positive electrode and porous active carbon as a negative electrode in an alkaline KOH aqueous electrolyte is fabricated. Owing to the synergetic effect between CoMoO4/Co9S8 and active carbon, CoMoO4/Co9S8//active carbon asymmetric supercapacitor exhibits an outstanding energy density of 42 Wh·kg−1 and an excellent cycling stability with 89.5% specific capacitance retained after 5000 cycles in an operating voltage of 1.6V. The facile synthesis route and remarkable supercapacitive performance of the CoMoO4/Co9S8 nanorod arrays is promising as a positive electrode materials for high-performance asymmetric supercapacitors.