Nitrogen and oxygen functionalized hollow carbon materials: The capacitive enhancement by simply incorporating novel redox additives into H2SO4 electrolyte

• Thiocarbanilide-derived N/O functionalized hollow carbon material (NPC) was synthesized.
• Rutin and pyrocatechol were used as redox additives for improving the capacitance of NPC-1.
• NPC-1-based symmetric supercapacitor exhibits prominent electrochemical performance.

In present work, we have developed a simple but effective template carbonization method for producing hollow carbon materials with high content of nitrogen and oxygen from thiocarbanilide. Among all samples, the NPC-1 exhibits high specific surface area (736 m2 g−1) and large pore volume (5.93 cm3 g−1) with high content of heteroatoms (∼11.25 at% nitrogen and ∼5.74 at% oxygen), which is conducive to the improvement of electrochemical performance. Specifically, the high specific capacitance and excellent cycling stability over 5000 cycles of the NPC-1-based electrode are achieved in 1 mol L−1 H2SO4 electrolyte. Additionally, pyrocatechol and rutin as novel redox additives that can easily cause redox-reactions have been incorporated into H2SO4 electrolyte to improve the capacitances. As a result, the NPC-1-R-0.15 and NPC-1-P-0.15 samples deliver high specific capacitances of 120.5 and 368.7 F g−1 at 2 A g−1, respectively, which are much higher than that of the NPC-1 sample (66.2 F g−1) without redox-additives at same current density. Furthermore, the large energy density of 18.9 and 11.9 Wh kg−1 of the NPC-1-based symmetric supercapacitors have been obtained in H2SO4+pyrocatechol and H2SO4+rutin electrolyte, respectively, and both samples also demonstrate excellent cyclic performance for 5000 cycles.