Potassium compound-assistant synthesis of multi-heteroatom doped ultrathin porous carbon nanosheets for high performance supercapacitors

Two-dimensional (2D) porous carbon materials have attracted great attentions as high-performance electrodes for supercapacitors due to their large aspect ratio and high surface area. Generally, micropore-dominant 2D carbon materials have higher densities than hierarchically porous 3D carbon materials, which can provide a new possibility of greatly enhancing the volumetric capacitance. Herein, we propose a facile and low-cost synthesis method of biomass-derived porous carbon nanosheets (PCNSs) with the assistance of the KOH derived potassium compounds using fish scale as precursor. The PCNS obtained at 600 °C possesses ultrathin nanosheet structure (with thickness of 3–5 nm), micropore-dominate porosity (with specific surface area of 962 m2 g−1), rich surface heteroatoms (14.64 at% for O, 5.05 at% for N and 0.92 at% for S) and high compacting density (1.06 g cm−3), which endow the electrodes with high gravimetric/volumetric capacitance performance in three-electrode and two-electrode systems.