Tunable growth of perpendicular cobalt ferrite nanosheets on reduced graphene oxide for energy storage

Ultrathin cobalt ferrite nanosheets have been successfully assembled on the surface of reduced graphene oxide (rGO) via only adjusting the volume ratio of ethanol and deionized (DI) water and a post calcination treatment. The perpendicular ultrathin cobalt ferrite nanosheets supported by rGO sheets (CoFe₂O₄ NSs@rGO) can be obtained when the volume ratio of ethanol and DI water is 10:30. Correspondingly, the hierarchical porous films covering the total rGO sheets will be formed nanosheets. When evaluated as the electrodes for lithium ion batteries (LIBs) and supercapacitors (SCs), the resultant CoFe₂O₄ NSs@rGO hybrids exhibit highly enhanced electrochemical performance. Even after 200 charge-discharge cycles at 400 mA g^-1, the electrodes as the anode material for LIBs still exhibit a reversible discharge capacity of 835.6 mAh g^-1. In addition, this electrode for SCs also exhibits specific capacitance of ca 1120 F g^-1 after 3000 cycles. These superior results imply that CoFe₂O₄ NSs with novel hybrid structure of rGO could potentially lead to an excellent electrochemical performance for energy storage.