Sonochemical assisted fabrication of 3D hierarchical porous carbon for high-performance symmetric supercapacitor

A scalable fabrication of 3D hierarchical porous carbon structure (3D-HPC) has been achieved via a simple sonochemical route at different pyrolysis temperatures. It is worth noting that all the 3D-HPC samples possess oxygen-functional groups after activation by KOH and self-doped by nitrogen, which are beneficial to improving their surface wettability as well as increasing the electro-active surface area between the electrode and the surrounding electrolyte, consequently enhancing their electrochemical performance. Remarkably, the resulting carbon sample pyrolyzed at 850 °C (AC-850) possesses a maximum doping level of 2.75 at% and a high surface area of 1376.19 m² g^-1, which exhibits high electrochemical performance with high capacitance up to 269.19 F g^-1 at a current density of 2 A g^-1. Moreover remarkably, the AC-850-based symmetric supercapacitor delivers a high energy density of 21.4 Wh kg^-1 at a power density of 531.2 W kg^-1 with excellent rate performance and superior cycling stability (94.7% retention over 5000 cycles). The present approach is very suitable for large scale production of high-quality porous carbon materials at low cost, which can be used in different aspects, such as energy storage, gas storage, environmental remediation, and so on.