Cyanometallic framework-derived hierarchical Co3O4-NiO/graphene foam as high-performance binder-free electrodes for supercapacitors

The cyanometallic framework (CMF)-derived bimetallic oxide/graphene foam (GF) composites were synthesized by a solution immersion and subsequent annealing treatment. As a binder-free electrode for supercapacitors, the Co3O4-NiO/GF electrode exhibited remarkable electrochemical properties in terms of high specific capacity (766 F g(-1) at 1 A g(-1)), superior rate capability with 67% capacitance retention (0.5-10 A g(-1)), as well as excellent cycling stability (86% retention after 5000 cycles). The improved capacitance performances were ascribed to the strong synergistic interaction between hierarchical Co3O4-NiO and GF substrate, where metal oxides contributed to high pseudocapacitance and GF provided outstanding conductivity and structural stability of electrodes.