Construction of zeolitic imidazolate frameworks-derived Ni_xCo_3−xO₄/reduced graphene oxides/Ni foam for enhanced energy storage performance

Direct assembling 2D zeolitic imidazolate frameworks-derived (ZIFs)-derived Ni-Co oxide on Ni foam (Ni_xCo_3−xO₄/Ni foam) is a very attractive way to obtain high performance for electrochemical energy storage device. In this work, the highly optimized Ni_xCo_3−xO₄/Ni foam was prepared via facile co-precipitation, ion-exchange method and subsequently composited with rGO, acting as binder-less electrode for high properties hybrid supercapacitors. As electrode materials, the pure Co₃O₄/Ni foam shows 94.40 C g⁻¹ (209.78 F g⁻¹) at 1 A g⁻¹, while the highly optimized Ni_xCo_3−xO₄/Ni foam exhibits a high capacity of 870.3 C g⁻¹ (1934F g⁻¹) at 1 A g⁻¹. Compared with Ni_xCo_3−xO₄/Ni foam, the reduced graphene oxides (rGO) modified Ni_xCo_3−xO₄/Ni foam electrodes possess a porous conductive structure, displaying more superior capacity of 1440.99 C g⁻¹ (3202.22F g⁻¹) at 1 A g⁻¹ and a higher cycling stability of 76.10% retention value after 1000 cycles. Subsequently, the Ni_xCo_3−xO₄/rGO/Ni foam electrodes were assembled as a hybrid supercapacitor, exhibiting a maximum energy density of 36.31 Wh kg⁻¹, a maximum power density of 8000 W kg⁻¹ and a good cycling stability of 76.29% retention value after 3000 cycles. The Ni_xCo_3−xO₄/rGO/Ni foam also could light the blue LED device. Thereby, it is proved that Ni_xCo_3−xO₄/rGO/Ni foam is a promising materials for hybrid supercapacitors.