Porous Carbon with Willow-Leaf-Shaped Pores for High-Performance Supercapacitors.

A novel kind of biomass-derived, high-oxygen-containing carbon material doped with nitrogen that has willow-leaf-shaped pores was synthesized. The obtained carbon material has an exotic hierarchical pore structure composed of bowl-shaped macropores, willow-leaf-shaped pores, and an abundance of micropores. This unique hierarchical porous structure provides an effective combination of high current densities and high capacitance because of a pseudocapacitive component that is afforded by the introduction of nitrogen and oxygen dopants. Our synthetic optimization allows further improvements in the performance of this hierarchical porous carbon (HPC) material by providing a high degree of control over the graphitization degree, specific surface area, and pore volume. As a result, a large specific surface area (1093 m2 g-1) and pore volume (0.8379 cm3 g-1) are obtained for HPC-650, which affords fast ion transport because of its short ion-diffusion pathways. HPC-650 exhibits a high specific capacitance of 312 F g-1 at 1 A g-1, retaining 76.5% of its capacitance at 20 A g-1. Moreover, it delivers an energy density of 50.2 W h kg-1 at a power density of 1.19 kW kg-1, which is sufficient to power a yellow-light-emitting diode and operate a commercial scientific calculator.