Hierarchical NiCo 2 S 4 Nanotube@NiCo 2 S 4 Nanosheet Arrays on Ni Foam for High‐Performance Supercapacitors

Hierarchical NiCo 2 S 4 nanotube@NiCo 2 S 4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm −2 is attained at 5 mA cm −2 , which is much higher than the specific capacitance values of NiCo 2 O 4 nanosheet arrays, NiCo 2 S 4 nanosheet arrays and NiCo 2 S 4 nanotube arrays on Ni foam. The hierarchical NiCo 2 S 4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm −2 . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo 2 S 4 electroactive materials are gradually corroded; however, the NiCo 2 S 4 phase can still be well‐maintained. Our results show that hierarchical NiCo 2 S 4 nanostructures are suitable electroactive materials for high performance supercapacitors.