Thermally oxidized synthesis of hierarchical Co3O4@MnO2 nanosheet arrays on nickel foam with enhanced supercapacitor performance

Pseudocapacitive materials, e.g. , MnO 2 and Co 3 O 4 , can significantly enhance the energy density of supercapacitors because of Faradaic reactions that can take place with these materials. Single-component electrodes have shown insufficient performance due to limited variations in electrode structures. Herein, we report a hierarchical electrode through growing networked Co 3 O 4 @MnO 2 hierarchical nanosheets (HNS) arrays directly on Ni foam. We adopt a one-step hydrothermal reaction followed by a simple staged post-annealing treatment which simplifies the synthesis procedure. When used as electrodes for supercapacitors, the Co 3 O 4 @MnO 2 HNS electrode shows good electrochemical performance, such as high areal/specific capacitances of 2.85 F cm −2 /2374 F g −1 at a current density of 1 mA cm −2 and long-term cycling stability of 4500 cycles. These encouraging results demonstrate this electrode design strategy is promising for developing high capacitance electrode materials for high energy density supercapacitors.