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 °C and alkali-activation at 700 °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.