Novel strategy for efficient conversion of biomass into N-doped graphitized carbon nanosheets as high-performance electrode material for supercapacitor

The transformation of low-cost, renewable and eco-friendly biomass into energy conversion or storage materials with high energy density is one of the effective means to alleviate the energy crisis. In this study, a scalable route was proposed to synthesize porous, hetero-atom doped graphitized carbon nanosheets from the biomass-fish scales, and the as-prepared material was further used to construct a high-performance electrode for supercapacitor application. The synthesized N-doped graphitized carbon nanosheets (GNC-900) exhibit an average scale of 1–2 μm in size and hierarchical porous structure with a specific surface area of 1261.5 m2 g−1. The results of cyclic voltammetry (CV) and galvanostatic charge-discharge show that GNC-900 owns the quasi-electric double layer capacitance behavior in 6.0 M KOH electrolyte due to the presence of heteroatoms, and it exhibits a distinguished specific capacitance value of 448 F g−1 at a current density of 1 A g−1 in three-electrode cell. The CV curves at different scan rates reveal that this electrode has superior reversible stability and rapid response. Meanwhile, it delivers a high energy density of 57.7 Wh kg−1 at a power density of 999 W kg−1 in a two-electrode system. This novel and low-cost strategy provides an effective route to transform fish scales into highly valuable electrode materials in energy storage fields.