Self-Template Synthesis of Multiheteroatom Codoped Porous Carbon with Rational Mesoporosity from Traditional Chinese Medicine Dregs for High-Performance Supercapacitors

As a biomass waste of therapy and health care discarded with millions of tons per year in Chinese people's daily life, traditional Chinese medicine dregs (MDs) are potential "zerocost", species-rich, and green raw materials for preparation of porous carbon (PC). Herein, multiheteroatoms (O, N, P, and S) self-codoped PCs are successfully prepared from MDs with their intrinsic metals as the self-template. The porosity can be controlled by purposefully mixing different types of MDs as feedstock. Under the optimum KOH activation, the as-prepared MDPC-2 exhibits a high specific surface area up to 2871 m(2) g-(1,) rational mesopore proportion of 47.3%, and appropriate contents of heteroatoms, which endow it with a high specific capacitance up to 486.2 F g(-1) at a current density of 1 A g(-1) for a three-electrode system in a 6 M KOH aqueous electrolyte. Most attractively, the MDPC-2-based symmetric supercapacitors deliver an energy density as high as 37.2 Wh kg(-1) at a power density of 558 W kg(-1) in a 1 M Na2SO4 aqueous electrolyte and a stronger energy output of 112.5 Wh kg-(1 )at a power density of 722 W kg(-1) in an EMIMBF4 ionogel electrolyte, with satisfactory rate retentions (62.3% in 1 M Na2SO4 and 64.8% in EMIMBF4 ionogel at 20 A g(-1)), as well as prominent cycling durabilities (98.1% and 96.9% after 10,000 cycles). The state-of-the-art electrochemical performances of MDPC-2 to date are due to the comprehensive considerations for specific surface area, pore size distribution, heteroatom effect, and effective combination of different type of MDs, which provide a meaningful protocol on scalable preparation of advanced biomass-derived PC for supercapacitors.