A popcorn-derived porous carbon optimized by thermal treatment and its outstanding electrochemical performance

A honeycomb-like porous carbon derived from low-cost popcorn was fabricated with a facile self-template strategy including pre-carbonization and chemical activation, and its corresponding thermal treatment temperatures are carefully discussed. Special attention was paid to the effect of the pre-carbonization temperature on its morphology, structure and electrochemical performance of the carbon material. The results showed the selection of the pre-carbonization temperature was crucial to the optimization of the microstructure and properties of capacitor carbon. The optimized popcorn-derived porous carbon fabricated by pre-carbonization at 600 degrees C and alkali-activation at 700 degrees C (PC-R6A7) possesses the most prominent merits in energy storage, containing unique honeycomb-like morphology, ultrahigh surface area (2361.25 m2 g-1), and moderate nitrogen content (1.8 at.%). These unique characteristics have favorable multiple synergistic effects, making PC-R6A7 suitable as the electrode materials for supercapacitors. In three-electrode configuration of 6 M KOH, PC-R6A7 shows an excellent capacity of 425 F g-1 at 1 A g-1 and still retains 350.2 F g-1 even at 20 A g-1, with an attractive retention rate of 82.4 %. The two-electrode based on PC-R6A7 also delivers a high capacity of 302 F g-1 and an impressive energy density of 10.5 Wh kg- 1 at a power density of 256 W kg- 1 at 1 A g-1 in 6 M KOH, and still retains energy density of 8.6 Wh kg- 1 at 7.4 KW kg- 1 at 20 A g-1. Furthermore, the capacitance of the PC-R6A7 keeps 92.0 % capacity after 10,000 cycles at 5 A g-1, and its coulomb efficiency is close to 100 %. In 1 M Li2SO4, PC-R6A7 also possesses an outstanding energy density of 26.2 Wh kg- 1 at the power source of 464.5 W kg- 1 at 1 A g-1 and still retains 14 Wh kg- 1 at 17.4 KW kg- 1 at 20 A g-1. The popcorn-derived porous carbon with excellent electrochemical property has great potential in the areas of energy-storage application.