Sustainable hierarchical porous biomass carbons enriched with pyridinic and pyrrolic nitrogen for asymmetric supercapacitor

Asymmetric supercapacitors usually possess higher energy density than symmetric supercapacitors. It's still a big challenge to synthesize low-cost and high-performance negative electrode active materials for the practical production of asymmetric supercapacitors. In this research, ginkgo leaf derived nitrogen-doped carbon was prepared and investigated as an electrode active material for the utilization in supercapacitors. Due to the hierarchical porous architecture, high N content, and ultrahigh ratio (86.5%) of pyridinic plus pyrrolic N species, the ginkgo leaf derived nitrogen-doped carbon material delivered a better specific capacitance (345 F g−1 at 0.2 A g−1) compared to pristine ginkgo leaf derived carbon and KOH-activated carbon without N-doping. Moreover, an asymmetric supercapacitor with this nitrogen-doped carbon as the negative electrode material also displayed an excellent energy density (42.2 Wh kg−1 at 700 W kg−1) and satisfactory electrochemical cycling reliability. In addition, these performances are also superior to those of some similar carbon materials, manifesting a good potential of this nitrogen-doped carbon to fabricate high-performance asymmetric supercapacitors.