Direct Dissolution of Cellulose in NaOH/Urea/α-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, α-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 (NSHPAs) were successfully obtained via directly dissolving cellulose in this ternary solvent, followed by gelling and carbonization. Because the fabricated carbon materials had a proper structure and a 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 contribution and pseudocapacitance contribution from the N,S dual doping were also analyzed. Meanwhile, they showed outstanding capacitance retention in a 2 M H2SO4 electrolyte. Additionally, a symmetric supercapacitor (SSC) was assembled by NSHPAs, and yielded a high specific capacitance of 63.6 F g-1 at 1 A g-1. At a power density of 130 W kg-1, the SSC showed a high energy density of 10.3 W h 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.