Construction of molybdenum dioxide nanosheets coated on the surface of nickel ferrite nanocrystals with ultrahigh specific capacity for hybrid supercapacitor

Recently, nickel ferrite with high theoretical capacity over the other metal oxide has been applied as electrode material for batteries and supercapacitors. However, owing to the serious aggregation and low specific surface area, the electrochemical performance of nickel ferrite (NiFe2O4) should be in urgent need of improvement. Here, we report the synthesis of unique molybdenum dioxide (MoO2) and nickel ferrite composite (MoO2/NiFe2O4) material via a facile strategy for the first time. The composite material presents a nanosheets-nanocrystals heterostructure. When evaluated as an electrode for hybrid supercapacitor in an alkaline solution, the MoO2/NiFe2O4 composite material presents a greatly enhanced specific capacity (2105 mA h/g at 4 A/g), which is better than those of individual component and exceeds some of the reported MoO2 and NiFe2O4 based electrodes. The capacity retention of MoO2/NiFe2O4 composite is about 81.1% after 1900 cycles. Such composite material also has great potential in other energy storage and conversion system.