Direct Dissolution of Cellulose in NaOH/Urea/alpha-Lipoic Acid Aqueous Solution to Fabricate All Biomass-Based Nitrogen, Sulfur Dual-Doped Hierarchical Porous Carbon Aerogels for Supercapacitors.

Using the disulfide bond and carboxyl group in the molecular structure, alpha-lipoic acid was easily dissolved in the NaOH/urea solution, and could be used as a ternary solvent for dissolving cellulose. Through this platform, N,S dual-doped hierarchical porous carbon aerogels (NSHPA) were successfully obtained via directly dissolving cellulose in this ternary solvent, followed by gelling, and carbonization. Because the fabricated carbon materials had the proper structure and uniform heteroatom doping, their capacitance could reach 329 F g-1 at 0.5 A g-1, 1647.5 mF cm-2 at 2.5 mA cm-2, and the fine rate property was 215 F g-1 at 10 A g-1, and 1075 mF cm-2 at 50 mA cm-2, respectively. Additionally, the electric double-layer capacitor (EDLC) contribution and pseudocapacitance contribution from the N, S dual doping were also analyzed. Meanwhile, they showed outstanding capacitance retention in 2 M H2SO4 electrolyte. Additionally, a symmetric supercapacitor (SSC) was assembled by NSHPA, and yielded a high specific capacitance of 63.6 F g-1 at 1 A g-1. At the power density of 130 W kg-1, the SSC showed high energy density of 10.3 Wh kg-1, and a long cycle life with 10% capacitance decay over 5000 cycles at 1 A g-1. These electrochemical performances suggest that this adopted synthesis route may open a novel avenue for the fabrication of heteroatom-doped carbon electrode materials, especially based on renewable and low-cost cellulose.