Nitrogen and oxygen Co-doped porous carbon derived from yam waste for high-performance supercapacitors

It is a considerable challenge to produce a supercapacitor with inexpensive raw materials and employ a simple process to obtain carbon materials with a high specific surface area, rich pore structure, and appropriate doping of heterogeneous elements. In the current study, yam waste-derived porous carbon was synthesized for the first time by a two-step carbonization and KOH chemical activation process. An ultra-high specific surface area of 2382 m² g^-1 with a pore volume of 1.11 cm³ g^-1 and simultaneous co-doping of O-N was achieved for the optimized sample. Because of these distinct features, the optimized material exhibits a high gravimetric capacitance of 423.23 F g^-1 at 0.5 A g^-1 with an impressive rate capability at 10 A g^-1, and prominent cycling durability with a capacity retention of 96.4% at a high current density of 10 A g^-1 after 10 000 cycles in 6 M KOH in a three-electrode system. Moreover, in 6 M KOH electrolyte, the assembled symmetrical supercapacitor provides a large C of 387.3 F g^-1 at 0.5 A g^-1. It also presents high specific energy of 34.6 W h kg^-1 when the specific power is 200.1 W kg^-1 and a praiseworthy specific energy of 8.3 W h kg^-1 when the specific power is 4000.0 W kg^-1 in 1 M Na₂SO₄ electrolyte. Thus, this study provides reference and guidance for developing high-performance electrode materials for supercapacitors.