Fabrication of Isomorphous Co 3 O 4 @Co 3 O 4 Hierarchical Core‐Shell Nanoneedles for High‐Performance Supercapacitors

Abstract Isomorphous Co 3 O 4 @Co 3 O 4 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 Co 3 O 4 nanosheets well coated on the surface of Co 3 O 4 nanoneedles. The isomorphous Co 3 O 4 @Co 3 O 4 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 Co 3 O 4 @Co 3 O 4 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.