Construction of Hierarchical CNT/rGO-Supported MnMoO₄ Nanosheets on Ni Foam for High-Performance Aqueous Hybrid Supercapacitors

Rationally designed conductive hierarchical nanostructures are highly desirable for supporting pseudocapacitive materials to achieve high-performance electrodes for supercapacitors. Herein, manganese molybdate nanosheets were hydrothermally grown with graphene oxide (GO) on three-dimensional nickel foam-supported carbon nanotube structures. Under the optimal graphene oxide concentration, the obtained carbon nanotubes/reduced graphene oxide/MnMoO₄ composites (CNT/rGO/MnMoO₄) as binder-free supercapacitor cathodes perform with a high specific capacitance of 2374.9 F g^-1 at the scan rate of 2 mV s^-1 and good long-term stability (97.1% of the initial specific capacitance can be maintained after 3000 charge/discharge cycles). The asymmetric device with CNT/rGO/MnMoO₄ as the cathode electrode and the carbon nanotubes/activated carbon on nickel foam (CNT-AC) as the anode electrode can deliver an energy density of 59.4 Wh kg^-1 at the power density of 1367.9 W kg^-1. These superior performances can be attributed to the synergistic effects from each component of the composite electrodes: highly pseudocapacitive MnMoO₄ nanosheets and three-dimensional conductive Ni foam/CNTs/rGO networks. These results suggest that the fabricated asymmetric supercapacitor can be a promising candidate for energy storage devices.