Covalent Triazine Frameworks Derived N/P/S‐Rich Carbon Nanosheets Enable Ultra‐high Capacity for Aqueous Redox‐Enhanced Supercapacitors ^†

Comprehensive Summary Controllable fabrication of multi‐electroactive sites and morphology‐ordered carbon electrodes with excellent capacity and alleviating self‐discharge behavior for aqueous redox‐enhanced supercapacitors (SC RE ) is highly desirable but still challenging. Herein, the N/P/S‐rich carbon nanosheets with ultrathin thickness (2–3 nm) and hierarchical porous structure are successfully prepared via phytic acid‐driven interfacial phosphorization strategy using S‐bridged covalent triazine framework nanosheets (CTFS) as precursor, which are synthesized through a eutectic molten salt‐induced ionothermal polymerization. The carbon electrode with adequate N/P/S active sites is pioneeringly introduced in SC RE , clarifying that the coupling hierarchical porous structure and multi‐electroactive sites can effectively enhance the interface interaction between carbon electrodes and redox electrolytes via the ex‐situ characterizations and theoretical calculations. Consequently, the resultant N/P/S‐rich carbon nanosheet (PCTFSC) enables SC RE in KI‐doped H 2 SO 4 electrolyte to achieve state‐of‐the‐art specific capacity (1586 mA·h·g –1 at 1 A·g –1 ) with 60% of capacity retention at 16 A·g –1 and ultra‐high energy density of 816 Wh·kg –1 , exceeding the reported aqueous supercapacitors thus far. Moreover, the PCTFS based SC RE also exhibits a low self‐discharge rate (holding 50% of open circuit potential after 15 h). This study provides new insights to design and regulate advanced carbon materials from the atom level and nano‐morphology toward high performance SC RE .