The fabrication of heteroatom-doped porous carbon materials with high electrical conductivity and large specific surface area via an environmentally friendly route is critical and challenging. Herein, nitrogen and oxygen co-doped agar porous carbon (APC) was developed for supercapacitors via a one-step carbonization method with agar as the raw material and ammonia as the activator and nitrogen source. APC outperformed pectin porous carbon, tamarind porous carbon, and the previously reported carbon-based supercapacitors with a high capacitance retention of 72% even from 0.5 A g-1 to 20 A g-1 and excellent cycling stability in 6 M KOH solution (retained after 10 000 cycles) with a rate of over 98.5%. Furthermore, the APC electrode-based symmetric device exhibited an impressive energy density of 20.4 W h kg-1 and an ultra-high power density of 449 W kg-1 in 1 M Na2SO4 electrolyte together with excellent cycling stability (103.2% primary capacitance retentivity after 10 000 cycles). This study offers a novel method for the synthesis of nitrogen heteroatom-doped hierarchical porous carbon materials for performance-enhanced energy storage devices.
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