Synthesis of NiMoO 4 @Co 3 O 4 hierarchical nanostructure arrays on reduced graphene oxide/Ni foam as binder-free electrode for asymmetric supercapacitor

Currently, substantial attention has been concentrated on the preparation and practical application of complex hierarchical nanostructure composite, which exhibits excellent electrochemical properties compared to the single-structured materials. Hence, a novel electrode of NiMoO4@Co3O4–5H composite nanoarrays supported on reduced graphene oxide/Ni Foam (rGO/NF) was synthesized through the facile hydrothermal method. The composite combines the advantages of the large specific capacitance of NiMoO4 and the great rate capability of Co3O4, exhibiting the distinguished specific capacitance and rate performance. The prepared NiMoO4@Co3O4–5H composite shows an enhanced pseudocapacitive performance of about 1722.3 F g−1 at a current density of 1 A g−1, and eminent rate capability of 80.8% at 10 A g−1. Moreover, the composite delivers good long-term cycling stability with capacitance retention of 91% after 6000 cycles. An asymmetric supercapacitor (ASC) was fabricated using NiMoO4@Co3O4–5H and AC as the positive electrode and negative electrode, achieving the high energy density of 37.1 Wh kg−1 at a power density of 798.0 W kg−1, and exceptional cycling stability (100% retention after 4000 cycles). These consequences suggest that NiMoO4@Co3O4–5H could be considered as a potential electrode material for energy storage devices.