Synthesis of Needle-like Nanostructure Composite Electrode of Co₃O₄/rGO/NF for High-Performance Symmetric Supercapacitor

In this work, a hierarchical electrode structure of cobaltosic oxide (Co₃O₄ ) growing on a reduced graphene oxide (rGO)-covered nickel foam (NF) substrate (named Co₃O₄/rGO/NF) is fabricated by a facile hydrothermal and subsequent annealing process. Thousands of nanoneedle units uniformly arranged on the surface of the rGO sheet stimulate the evident increase in the specific surface area and thus produce more active sites. Because of the special hierarchical structure, the Co₃O₄/rGO/NF electrode shows a high specific capacitance of 1400 F g⁻¹ at 1 A g⁻¹ and retains 58% capacitance even when the current density increases to 30 A g⁻¹ . In addition, a symmetric supercapacitor based on the Co₃O₄/rGO/NF electrode is assembled, exhibiting high specific capacitance of 311 F g⁻¹ at 1 A g⁻¹, as well as remarkable power density and energy density (40.67 Wh kg⁻¹ at 12 kW kg⁻¹ ). The device also demonstrates a great cycling performance after 10,000 cycles under the current density of 10 A g⁻¹, acquiring 89.69% capacitance retention of the initial state. The accessible synthetic method and superior electrochemical performance of the Co₃O₄/rGO/NF composite electrode implicate its extensive application prospects in terms of new energy storage.