Advanced asymmetric supercapacitor based on molybdenum trioxide decorated nickel cobalt oxide nanosheets and three-dimensional α-FeOOH/rGO

Highlights: • MoO₃/NiCo₂O₄-NSs and α-FeOOH/rGO were prepared via a simple wet-chemical strategy. • MoO₃/NiCo₂O₄-NSs show high surface area, fast ion transfer, and good structural stability. • MoO₃/NiCo₂O₄-NSs presented enhanced specific capacity, rate, and cycling performance. • An ASC device exhibited a high capacity with a wide potential window. • MoO₃/NiCo₂O₄-NSs//α-FeOOH/rGO delivered an ultrahigh energy density of 50.2 Wh kg⁻¹. -- Abstract: Unique molybdenum trioxide decorated nickel-cobalt oxide nanostructures (MoO₃/NiCo₂O₄-NSs) and three-dimensional hierarchical structure α-FeOOH/rGO film were prepared via facile hydrothermal and annealing strategies. Owing to the merits of the large surface area, superior ionic conductivity, increased availability of active sites/interfaces, rich mixed valences of polymetallic oxide and the favorable structural stability, the as-prepared optimized battery-type MoO₃/NiCo₂O₄-NSs electrode material presents an extraordinary specific capacity (1042 F g⁻¹ at 1 A g⁻¹), largely improved rate capability (93%, from 1 to 6 A g⁻¹), and superior cycling performance, compared with the NiCo₂O₄–NCs, MoO₃, and also exceeds some of the reported Ni-, Co-based electrodes. Underlying such great improvement, a MoO₃/NiCo₂O₄-NSs//α-FeOOH/rGO asymmetric supercapacitor device with a large potential window was assembled, which delivered a high capacitance of 141 F g⁻¹ at 1 A g⁻¹, an excellent energy density of 50.2 Wh kg⁻¹, and an amazing power density of 4.8 kW kg⁻¹. The serially connected asymmetric supercapacitor can power commercial light-emitting diodes suggesting their potential application for electronic gadgets. The superior energy storage characteristics of the asymmetric supercapacitor are strongly attributed to the interconnected 3D nanoporous network architectures of the MoO₃/NiCo₂O₄-NSs and the good compatibility with the α-FeOOH/rGO negative electrode.