Facile synthesis of hierarchical Co3O4@MnO2 core–shell arrays on Ni foam for asymmetric supercapacitors

Abstract

Hierarchical Co3O4@MnO2 core–shell arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the electrode for high-performance supercapacitors. Owing to the high conductivity of the well-defined mesoporous Co3O4 nanowire arrays in combination with the large surface area provided by the ultrathin MnO2 nanosheets, the unique designed Co3O4@MnO2 core–shell arrays on Ni foam have exhibited a high specific capacitance (560 F g−1 at a current density of 0.2 A g−1), good rate capability, and excellent cycling stability (95% capacitance retention after 5000 cycles). An asymmetric supercapacitor with Co3O4@MnO2 core–shell nanostructure as the positive electrode and activated microwave exfoliated graphite oxide activated graphene (MEGO) as the negative electrode yielded an energy density of 17.7 Wh kg−1 and a maximum power density of 158 kW kg−1. The rational design of the unique core–shell array architectures demonstrated in this work provides a new and facile approach to fabricate high-performance electrode for supercapacitors.