In situ synthesis of Fe2O3 nanosphere/Co3O4 nanowire-connected reduced graphene oxide hybrid networks for high-performance supercapacitors.

Abstract

Three-dimensional (3D) hybrid networks consisting of reduced graphene oxide (rGO) sheets interconnected by Co3O4 nanowires (rGO/Co3O4), followed by the decoration of Fe2O3 nanospheres (NSs) (rGO/Co3O4@Fe2O3), were demonstrated by a facile hydrothermal method, with which the rGO/Co3O4 networks acted as nucleation sites for the in situ synthesis of Fe2O3 NSs. The intimate contacts between rGO, Co3O4 NWs and Fe2O3 NSs, which result in an excellent conductive behavior, provide a unique structure with huge potential for electrochemical property promoted electrochemical supercapacitors. The rGO/Co3O4@Fe2O3 hybrid networks as electrodes exhibit a high capacitance of 784 F g-1 at 1 A g-1 with 83% retention of the initial capacitance as the current density increases from 1 to 10 A g-1, which is explained by the graphene-based interconnected structure owing to the advantages of accommodating the volume expansion between Co3O4 NWs and Fe2O3 NSs. The supercapacitor was assembled by applying a nickel aluminum layered double hydroxide (NiAl-LDH) structure and rGO/Co3O4@Fe2O3 as the electrode materials and yields an energy density of 70.78 W h kg-1 at a power density of 0.29 kW kg-1. The energy density can maintain 24.24 W h kg-1 with 9.94 kW kg-1.