Facile and green synthesis of biomass-derived N, O-doped hierarchical porous carbons for high-performance supercapacitor application

The development of superior electrode materials using biomass as sustainable carbon sources is of great significance in promoting the practical application of supercapacitors. Herein, we prepared a N, O co-doped hierarchical porous carbon (GPC-0.9 N) with an ultra-high specific surface area of 2808.65 m2 g-1 and abundant microporous, mesoporous and macroporous structures through the straightforward pre-carbonization method using garlic peels combined with KHCO3/melamine activation. Additionally, the relatively high nitrogen (3.81%) and oxygen content (4.79%) can enhance the wettability of the carbon materials and introduce additional pseudocapacitance. As a result, the electrode material achieved a high specific capacitance of 396.25 F g-1 at 1 A g-1 and outstanding rate capability of 283.13 F g-1 at 25 A g-1 in 6 M KOH electrolyte in a three-electrode system. Meanwhile, the symmetrical supercapacitor based on the GPC-0.9 N electrode material showed a high energy density of 9.07 Wh kg-1 at the power density of 309.2 W kg-1. Furthermore, it exhibited excellent cycling stability, with 92.5% of the capacitance retained after 10000 cycles at 10 A g-1. This research provides insights for the rational design of a green, renewable and eco-friendly biomass-derived porous carbon that can be widely used as supercapacitor electrode materials in the future.