An ultrasonic-assisted synthesis of rice-straw-based porous carbon with high performance symmetric supercapacitors.

Biomass porous carbon materials are ideal supercapacitor electrode materials due to their low price, rich source of raw materials and environmental friendliness. In this study, an ultrasonic-assisted method was applied to synthesize the rice-straw-based porous carbon (UPC). The obtained UPC exhibited a two-dimensional structure and high specific surface area. In addition, the electrochemical test results showed that the UPC with a 1 hour ultrasonic treatment and lower activation temperature of 600 °C (UPC-600) demonstrated optimal performance: high specific capacitances of 420 F g-1 at 1.0 A g-1 and 314 F g-1 at a high current of 10 A g-1. Significantly, the symmetric supercapacitors showed a high energy density of 11.1 W h kg-1 and power density of 500 W kg-1. After 10 000 cycles, 99.8% of the specific capacitance was retained at 20 A g-1. These results indicate that UPC-600 is a promising candidate for supercapacitor electrode materials.