From double-helix structured seaweed to S-doped carbon aerogel with ultra-high surface area for energy storage

:A sustainable biomass conversion and green strategy, using red algae derived carrageenan-Fe hydrogel as precursor, is developed to fabricate the 3D hierarchical macro-meso-microporous sulfur-doped carbon aerogel (HPSCA) with tunable nanopores and ultra-high surface area up to 4037.0 m2 g−1. The molecular-level dispersions of Fe3+ ions in carrageenan contribute to the ultra-high surface area of HPSCA after carbonization, acid washing and activation process. The attracting structure features make it an applicable candidate material in lithium-sulfur (Li-S) batteries and double-layer supercapacitors (SCs). The highly developed porous structure of HPSCA can accommodate more sulfur (up to 80 wt%) to produce high-energy composite cathode with high specific capacity, cycle stability and long cycle life (400 cycles) in Li-S batteries. Meanwhile, HPSCA can present high specific capacitance of 335 and 217 F g−1 (1 A g−1) in the aqueous and organic electrolyte. Superior rate performance also can be obtained, and high capacitance of 204 F g−1 at 100 A g−1 and 173 F g−1 at 50 A g−1 in aqueous and organic electrolytes, respectively, is retained.