3D mesoporous hybrid NiCo2O4@graphene nanoarchitectures as electrode materials for supercapacitors with enhanced performances

Abstract

3D mesoporous hybrid NiCo₂O₄@graphene nanoarchitectures were successfully synthesized by a combination of freeze drying and hydrothermal reaction. Field-emission scanning electron microscopy (FESEM) and TEM analyses revealed that the NiCo₂O₄@graphene nanostructures consist of a hierarchical mesoporous sheet-on-sheet nanoarchitecture with a high specific surface area of 194 m² g⁻¹. Ultrathin NiCo₂O₄ nanosheets, with a thickness of a few nanometers and mesopores ranging from 2 to 5 nm, were wrapped in graphene nanosheets and hybrid nanoarchitectures were formed. When applied as electrode materials in supercapacitors, the hybrid NiCo₂O₄@graphene nanosheets exhibited a high capacitance of 778 F g⁻¹ at a current density of 1 A g⁻¹, and an excellent cycling performance extending to 10 000 cycles at a high current density of 10 A g⁻¹.