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.
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