Fabrication of Isomorphous Co3 O4 @Co3 O4 Hierarchical Core-Shell Nanoneedles for High-Performance Supercapacitors

Isomorphous Co3O4@Co3O4 core-shell hierarchical nanoneedles are fabricated through a simple two-step hydrothermal process associated with an annealing treatment. The unique nanoarchitecture consists of a layer of isomorphous Co3O4 nanosheets well coated on the surface of Co3O4 nanoneedles. The isomorphous Co3O4@Co3O4 core-shell hierarchical nanostructures exhibit a remarkable capacitance of 973.6 F g−1 at a current density of 1 A g−1 owing to the isomorphous core-shell hierarchical architecture and porous feature. Moreover, an asymmetric supercapacitor device based on the hierarchical Co3O4@Co3O4 core-shell nanostructure and porous carbon is fabricated and exhibits a desirable high energy densities with a value of 137.96 Wh kg−1 at a power density of 0.32 kW kg−1. These results indicate that the as-prepared nanomaterials are outstanding candidates for electrochemical supercapacitors.