Fabrication of Hierarchical NiMoO 4 /NiMoO 4 Nanoflowers on Highly Conductive Flexible Nickel Foam Substrate as a Capacitive Electrode Material for Supercapacitors with Enhanced Electrochemical Performance

Hierarchical NiMoO 4 /NiMoO 4 nanoflowers were fabricated on highly conductive flexible nickel foam (NF) substrates using a facile hydrothermal method to achieve rapid charge-discharge ability, high energy density, long cycling lifespan, and higher flexibility for high-performance supercapacitor electrode materials. The synthesized composite electrode material, NF/NiMoO 4 /NiMoO 4 with a nanoball-like NF/NiMoO 4 structure on a NiMoO 4 surface over a NF substrate, formed a three-dimensional interconnected porous network for high-performance electrodes. The novel NF/NiMoO 4 /NiMoO 4 nanoflowers not only enhanced the large surface area and increased the electrochemical activity, but also provided an enhanced rapid ion diffusion path and reduced the charge transfer resistance of the entire electrode effectively. The NF/NiMoO 4 /NiMoO 4 composite exhibited significantly improved supercapacitor performance in terms of a sustained cycling life, high specific capacitance, rapid charge-discharge capability, high energy density, and good rate capability. Electrochemical analysis of the NF/NiMoO 4 /NiMoO 4 nanoflowers fabricated on the NF substrate revealed ultra-high electrochemical performance with a high specific capacitance of 2121 F g −1 at 12 mA g −1 in a 3 M KOH electrolyte and 98.7% capacitance retention after 3000 cycles at 14 mA g −1 . This performance was superior to the NF/NiMoO 4 nanoball electrode (1672 F g −1 at 12 mA g −1 and capacitance retention 93.4% cycles). Most importantly, the SC (NF/NiMoO 4 /NiMoO 4 ) device displayed a maximum energy density of 47.13 W h kg −1 , which was significantly higher than that of NF/NiMoO 4 (37.1 W h kg −1 ). Overall, the NF/NiMoO 4 /NiMoO 4 composite is a suitable material for supercapacitor applications.