Hierarchical heterostructures of MnO2 nanosheets or nanorods grown on Au-coated Co3O4 porous nanowalls for high-performance pseudocapacitance

Abstract

The rational design and fabrication of more multi-component (material-combination) 3D hierarchical heterostructures for high-performance pseudocapacitor applications still remains a challenge. Herein, we have designed and synthesized a 3D hierarchical heterostructure of MnO₂ nanosheets or nanorods grown on an Au-coated Co₃O₄ porous nanowall array, resembling a sandwich configuration of Co₃O₄@Au@MnO₂, by a facial and controllable electrochemical deposition process. Due to their unique self-assembling architecture and characteristics including porous Co₃O₄ nanowalls, ultrathin MnO₂ nanosheets, and a high conductivity Au layer sandwiched between them, each component provides a much-needed critical function for the efficient use of metal oxides for energy storage. The synthesized 3D hierarchical heterostructures exhibited favorable electrochemical performances, such as a high specific capacitances of 851.4 F g⁻¹ at 10 mV s⁻¹ and 1532.4 F g⁻¹ at 1 A g⁻¹, good rate performance and an excellent long-term cycling stability (almost no degradation after 5000 cycles), which are better than those of the reported Co₃O₄ or MnO₂ based electrode materials, and thus could be considered as perspective materials for high-performance electrochemical capacitors.