High performance hierarchical porous carbon derived from distinctive plant tissue for supercapacitor

It is generally acknowledged that the activation method and component of the precursor are of great importance for making porous carbon. In this study, four plant materials belong to one genus were selected as optimized plant material to produce hierarchical porous carbon for supercapacitors, the influence of initial structure was discussed. All the produced porous carbons have large specific surface area (higher than 2342 m² g^-1), high microporosity (more than 57%), and high pore volume (larger than 1.32 cm³ g^-1). All the samples show characteristic of electrical double layer capacitance, and the onion-based porous carbon obtain highest specific capacitance of 568 F g^-1 at the current density of 0.1 A g^-1. With the current density rising from 1 A g^-1 to 50 A g^-1, the specific capacitance only decreases for 20%. After 5000 cycles, all the samples show relatively high capacitance retention (up to 97%). Two-step acid pickling has washed most impurities and directly lead to small equivalent series resistance (lower than 0.2 Ω). The samples show high power density and energy density (71 W h kg^-1@180 W kg^-1, 210 kW kg^-1@33 W h kg^-1). This study open an avenue to create high-performance hierarchical porous carbon based on plant architecture.