Biocarbons are difficult to graphitize even at 3000 °C. In this study, three-dimensional porous graphene-like sheets (3DPGLS) were directly synthesized from biocarbons at 900 °C. Potassium carbonate was utilized as a catalyst to release graphite microcrystals from the crosslinked sp³ carbon atoms in the hard carbon phase, and subsequently recrystallized them to form graphene layers. The as-obtained 3DPGLS showed a high purity and low defect density, and possessed high conductivity (32.14 S cm⁻¹) and specific surface area (1506.19 m² g⁻¹). Without conductive additives, the capacitance of 3DPGLS reached 91.15 F g⁻¹ at a current density of 0.2 A g⁻¹ acting as a two-electrode symmetrical supercapacitor electrode material in an organic electrolyte. 85.1% of the initial capacitance was maintained after 5000 cycles at a current density of 0.1 A g⁻¹.

KFe ^II [Fe ^III (CN) ₆ ] with a symmetric cubic structure exhibits exceptional electrochemical performance based on a solid solution mechanism, and its high structural stability and electrochemical reversibility.