Synchronously boosting gravimetric and volumetric performance: Biomass-derived ternary-doped microporous carbon nanosheet electrodes for supercapacitors

Porous carbon materials are the most widely used electrode materials in supercapacitors. Numerous works focus on increasing specific surface area and engineering hierarchical porosity as well as doping heteroatoms to improve the gravimetric performance for porous carbon electrodes. However, highly porous structures will cause low density for porous carbon electrodes, resulting in poor volumetric performance. The complex synthesis methods also restrict the wide applications of the resultant carbons. In this work, we demonstrate a sustainable and efficient strategy to synthesize ternary-doped microporous carbon nanosheets via treating fish skin with KOH. Notably, KOH firstly turns the fish skin into water-soluble gelatin, then KOH-derived potassium compounds simultaneously act as templates and activators to form micropore-dominant carbon nanosheets. The precursor (fish skin) and reagent (KOH) are low-cost, and potassium compound in the resultant carbons (K2CO3) is low-toxicity and easy-disposal. The relatively low pyrolysis temperature (600 °C) reserves numerous O, N and S heteroatoms derived from fish skin and leads to rational specific surface area, pore volume and compacting density of the porous carbon nanosheets. Beneficial from the unique nanostructure and rich surface heteroatoms, the resultant carbon shows integrated high gravimetric and volumetric performance as electrode for supercapacitor in aqueous electrolyte.