Fabrication of hierarchical MnMoO4•H2O@MnO2 core-shell nanosheet arrays on nickel foam as an advanced electrode for asymmetric supercapacitors

The hierarchical MnMoO4 center dot H2O@MnO2 core-shell nanosheet arrays on nickel foam have been successfully fabricated by a mild two-step hydrothermal method. MnMoO4 center dot H2O@MnO2 nanosheet arrays is synthesized by adding sodium molybdates solution into the manganese chloride solution containing a nickel foam, and followed by the first step hydrothermal treatment. The MnMoO4 center dot H2O@MnO2 is fabricated by the second step hydrothermal treatment of above-step product in potassium permanganate solution. The core-shell nanosheet structure significantly increases the amount of active sites for redox reactions, shortens the diffusion pathway for ions, and facilitates the effective penetration of the electrolytes for energy storage application. The MnMoO4 center dot H2O@MnO2 as electrode material reaches to a high specific capacitance of 3560.2 F g(-1) at a current density 1 A g(-1), as well as advantageous cycling stability (84.1% capacitance retention after 10,000 cycles). Furthermore, an asymmetric supercapacitor is also assembled, exhibiting an energy density of 45.6 Wh kg(-1) at a power density of 507.3 W kg(-1). The MnMoO4 center dot H2O@MnO2 is a promising electrode material for supercapacitors.