Single-pot hydrothermal synthesis of copper molybdate nanosheet arrays as electrode materials for high areal-capacitance supercapacitor

Supercapacitors have attracted significant attention due to the fast charge-discharge ability, excellent rate capability, and long-time stability. In the following study, for the first time, copper molybdate nanosheets (CuMoO4 NSs) grown on nickel foam (NF) have been successfully constructed by a single-pot hydrothermal method. The as-obtained nickel-foam based copper molybdate nanosheets can be directly used as the electrode for the supercapacitors. The electrochemical properties of the CuMoO4 NSs as binder-free electrode for supercapacitor was examined by cyclic voltammetry (CV), galvanostatic charge, and discharge analysis (GCD), electrochemical impedance spectroscopy (EIS), and cycle life measurements in 2 M KOH electrolyte. The GCD analysis exhibited a high specific capacitance of 2259.55 F g(-1) at 1 A g(-1), and good rate capability (1260.14 F g(-1) at 45 A g(-1)) in a 2 M KOH electrolyte. The cyclic stability analysis showed excellent cycling stability of 90.08% capacitance retention after 5000 GCD cycles at 16 A g(-1), together with similar to 100% coulomb efficiency. Moreover, an asymmetric supercapacitor was fabricated using CuMoO4 NSs on Ni foam (CuMoO4 NSs/NF) as the positive electrode, and activated carbon on Ni foam (AC/NF) as the negative electrode. The device displayed an operation voltage of 1.2 V, and high specific energy of 52.51 Wh kg(-1) at a specific power of 600 W kg(-1). Moreover, the device exhibited good cycling stability of 78.6% capacitance retention after 5000 cycles at 4 A g(-1). Also, the asymmetric device displays improved low self-discharge behavior by charging it at an optimal current density and time, and the self-discharge is greatly suppressed due to the presence of 3D network of CuMoO4 NSs grown on nickel foam. This work demonstrates that CuMoO4 NSs could be a promising electrode for high-performance energy storage devices.