Spreading GO nanosheets-coated nickel foam decorated by NiCo2O4/NiCo2S4 nanoarrays for high-performance supercapacitor electrodes

Abstract

Porous nickel foam (NF) is often wrapped by reduced graphene oxide (rGO) for loading active nanomaterials. To clarify the influence of the dispersion of graphene nanosheets in NF framework on the electrochemical performance, herein, spreading GO nanosheets-coated NF (NF@sGO) is developed via negative pressure immersion method, in which, GO sheets spreading on the macropores adjust the pore structure and enlarge the supporting surface of NF framework. Compared to the NF@rGO prepared by hydrothermal method, NF@sGO scaffold exhibits a high capacitance for the pseudocapacitance contributed by GO. Acting as a porous scaffold for growing NiCo2O4 nanoneedles, the NF@sGO/NiCo2O4 composite delivers a specific capacitance of 2522 F g−1 (1135 C g−1) at 1 A g−1, much higher than that of the control sample NF@rGO/NiCo2O4. To further improve the electrochemical performance of NF@sGO/NiCo2O4, thin NiCo2S4 nanosheets are decorated on NiCo2O4 nanoneedles. Optimized NF@sGO/NiCo2O4/NiCo2S4-0.02 sample delivers a maximum specific capacitance of 2980 F g−1 (1341 C g−1) at 1 A g−1 and a superior long-term cycling stability. The performances of NF@sGO/NiCo2O4 and NF@sGO/NiCo2O4/NiCo2S4-0.02 are both higher than existing composites. The superior electrochemical performance is attributed to the combination of novel NF@sGO scaffold and NiCo2O4 nanoneedles or optimized NiCo2O4/NiCo2S4 hybrid nanostructures. In view of the easy preparation and superior performance, NF@sGO scaffold has a promising prospect for preparing high-performance integrated electrodes.