Binder-free electrodes of NiMoO4/graphene oxide nanosheets: synthesis, characterization and supercapacitive behavior

Abstract

In the present work we report a facile and efficient hydrothermal method to fabricate a nanocomposite of NiMoO₄ and graphene nanosheets (NiMoO₄/GNS) on a nickel foam (NF) substrate. The nanocomposite displayed good mechanical strength. Interestingly, NiMoO₄/GNS/NF was employed as a binder-free electrode for supercapacitor application. The NiMoO₄/GNS/NF electrode with high electrical conductivity showed a remarkable electrochemical performance compared to a pure NiMoO₄ electrode. Herein, the role of the GNS was investigated in the electrochemical behavior of the electrode. A maximum specific capacitance of 3868 F g⁻¹ at 2 A g⁻¹ discharge current was obtained for the NiMoO₄/GNS/NF electrode. Notably, the NiMoO₄/GNS/NF electrode preserved almost 76% of its maximum capacitance at a high current density of 30 A g⁻¹, which indicates the high-rate capability of the electrode material. Also, the NiMoO₄/GNS/NF electrode maintained at least 98% of its initial capacitance after 4000 operational cycles. Moreover, an asymmetric supercapacitor was assembled using NiMoO₄/GNS/NF in combination with a reduced graphene oxide (rGO)/NF electrode. The fabricated device showed excellent performance with high energy/power density and long cycling stability. It was concluded that such an excellent supercapacitive performance originates from the three-dimensional structure of the nanosheets and the intimate contact between NiMoO₄ and the GNS. This work suggests that the NiMoO₄/GNS/NF electrode is an exciting electrode material for energy storage purposes.