Free-standing hierarchical Co@CoO/CNFs/Cu-foam composite based on electrochemical deposition as high-performance supercapacitor electrode

Three-dimensional structural materials with sufficient reactive contact surface to the electrolyte can significantly improve the capacitance performance of supercapacitors. Herein, we report a facile method to fabricate a hierarchical carbon nanofibers (CNFs) modified Cu-foam supported Co@CoO hybrid as a free-standing and binder-free electrode for supercapacitor application. The optimized Co@CoO/CNFs/Cu-foam shows a high specific capacitance of 19.2 F cm−3 at the current density of 50 mA cm−3 and a remarkable capacitance retention of 97.5% after 5000 cycles in a 3-electrode system. A button-type asymmetric supercapacitor was additionally constructed by using Co@CoO/CNFs/Cu foam as the positive electrode and activated carbon electrode as negative electrode to examine its practical application. The stored energy density reached to 180.5 mWh cm−2 with the corresponding power density of 6000 mW cm−2 at a discharging current density of 4 mA cm−2. An excellent cycling life of retention 100% was maintained after 5000 cycles. The high-surface area and conductivity of the CNFs played a positive role as support to highly-dispersed Co@CoO nanoparticles. The pulsed electrodeposition additionally favored the controllable fabrication of Co@CoO nanoparticles with homogeneously distribution and uniform sizes. The hierarchical hybrid electrode with porous architecture eventually allowed good access of electrolyte and efficient charge storage and transfer, which concomitantly improved its overall electrochemical performance.