One-step preparation of N,O co-doped 3D hierarchically porous carbon derived from soybean dregs for high-performance supercapacitors

Hierarchically porous carbon (HPC) material based on environmental friendliness biomass has spurred much attention, due to its high surface area and porous structure. Herein, three-dimensional (3D) N,O co-doped HPC (N-O-HPC) was prepared by using a one-step fabrication process of simultaneously carbonizing and activating soybean dregs and used as an electrode for supercapacitors (SCs). The obtained N-O-HPC with 4.8 at% N and 6.1 at% O exhibits a pretty small charge transfer resistance (0.05 Ω) and a large specific capacitance (408 F g^-1 at 1 A g^-1), due to its 3D hierarchically porous framework structure with extremely large specific surface area (1688 m² g^-1). Moreover, a symmetrical SC assembled with the HPC electrode exhibits an amazingly high energy density (22 W h kg^-1 at 450 W kg^-1) and a stable long cycling life with only 6% capacitance loss after 5000 cycles in 1 M Na₂SO₄ solution. This work provides a facile, green, and low-cost way to prepare electrode materials for SCs.