Growth of zinc cobaltate nanoparticles and nanorods on reduced graphene oxide porous networks toward high-performance supercapacitor electrodes

A type of composite network constructed from zinc cobaltate (ZnCo2O4) nanoparticles and nanorods on reduced graphene oxide (rGO) nanosheets has been prepared by a facile hydrothermal method. Transmission electron microscope results reveal that the rGO nanosheets are covered by ZnCo2O4 nanoparticles evenly due to the abundant surface functional groups on surface of original GO, and supported by some cross-linked ZnCo2O4 nanorods in the entire structures. With a rational combination, the composite networks present a meso-/macroporous architecture with a larger specific surface area than those of pristine ZnCo2O4 nanorods. As expected, the prepared ZnCo2O4/rGO electrode exhibits improved electrochemical performances, which shows a high specific capacitance (626 F g−1 at 1 A g−1), excellent rate capability (81% retention of the initial capacitance at 30 A g−1), and long-term cycling stability (99.7% retention after 3000 cycles at 10 A g−1). Such remarkable electrochemical performances of ZnCo2O4/rGO electrode can be due to the effective pathways for both electronic and ionic transport in these porous networks.